text: // SPDX-License-Identifier: GPL-2.0-or-later
  /*
   * raid5.c : Multiple Devices driver for Linux
   *	   Copyright (C) 1996, 1997 Ingo Molnar, Miguel de Icaza, Gadi Oxman
   *	   Copyright (C) 1999, 2000 Ingo Molnar
   *	   Copyright (C) 2002, 2003 H. Peter Anvin
   *
   * RAID-4/5/6 management functions.
   * Thanks to Penguin Computing for making the RAID-6 development possible
   * by donating a test server!
   */
  
  /*
   * BITMAP UNPLUGGING:
   *
   * The sequencing for updating the bitmap reliably is a little
   * subtle (and I got it wrong the first time) so it deserves some
   * explanation.
   *
   * We group bitmap updates into batches.  Each batch has a number.
   * We may write out several batches at once, but that isn't very important.
   * conf->seq_write is the number of the last batch successfully written.
   * conf->seq_flush is the number of the last batch that was closed to
   *    new additions.
   * When we discover that we will need to write to any block in a stripe
   * (in add_stripe_bio) we update the in-memory bitmap and record in sh->bm_seq
   * the number of the batch it will be in. This is seq_flush+1.
   * When we are ready to do a write, if that batch hasn't been written yet,
   *   we plug the array and queue the stripe for later.
   * When an unplug happens, we increment bm_flush, thus closing the current
   *   batch.
   * When we notice that bm_flush > bm_write, we write out all pending updates
   * to the bitmap, and advance bm_write to where bm_flush was.
   * This may occasionally write a bit out twice, but is sure never to
   * miss any bits.
   */
  
  #include <linux/blkdev.h>
  #include <linux/kthread.h>
  #include <linux/raid/pq.h>
  #include <linux/async_tx.h>
  #include <linux/module.h>
  #include <linux/async.h>
  #include <linux/seq_file.h>
  #include <linux/cpu.h>
  #include <linux/slab.h>
  #include <linux/ratelimit.h>
  #include <linux/nodemask.h>
  
  #include <trace/events/block.h>
  #include <linux/list_sort.h>
  
  #include "md.h"
  #include "raid5.h"
  #include "raid0.h"
  #include "md-bitmap.h"
  #include "raid5-log.h"
  
  #define UNSUPPORTED_MDDEV_FLAGS	(1L << MD_FAILFAST_SUPPORTED)
  
  #define cpu_to_group(cpu) cpu_to_node(cpu)
  #define ANY_GROUP NUMA_NO_NODE
  
  static bool devices_handle_discard_safely = false;
  module_param(devices_handle_discard_safely, bool, 0644);
  MODULE_PARM_DESC(devices_handle_discard_safely,
  		 "Set to Y if all devices in each array reliably return zeroes on reads from discarded regions");
  static struct workqueue_struct *raid5_wq;
  
  static inline struct hlist_head *stripe_hash(struct r5conf *conf, sector_t sect)
  {
  	int hash = (sect >> RAID5_STRIPE_SHIFT(conf)) & HASH_MASK;
  	return &conf->stripe_hashtbl[hash];
  }
  
  static inline int stripe_hash_locks_hash(struct r5conf *conf, sector_t sect)
  {
  	return (sect >> RAID5_STRIPE_SHIFT(conf)) & STRIPE_HASH_LOCKS_MASK;
  }
  
  static inline void lock_device_hash_lock(struct r5conf *conf, int hash)
  {
  	spin_lock_irq(conf->hash_locks + hash);
  	spin_lock(&conf->device_lock);
  }
  
  static inline void unlock_device_hash_lock(struct r5conf *conf, int hash)
  {
  	spin_unlock(&conf->device_lock);
  	spin_unlock_irq(conf->hash_locks + hash);
  }
  
  static inline void lock_all_device_hash_locks_irq(struct r5conf *conf)
  {
  	int i;
  	spin_lock_irq(conf->hash_locks);
  	for (i = 1; i < NR_STRIPE_HASH_LOCKS; i++)
  		spin_lock_nest_lock(conf->hash_locks + i, conf->hash_locks);
  	spin_lock(&conf->device_lock);
  }
  
  static inline void unlock_all_device_hash_locks_irq(struct r5conf *conf)
  {
  	int i;
  	spin_unlock(&conf->device_lock);
  	for (i = NR_STRIPE_HASH_LOCKS - 1; i; i--)
  		spin_unlock(conf->hash_locks + i);
  	spin_unlock_irq(conf->hash_locks);
  }
  
  /* Find first data disk in a raid6 stripe */
  static inline int raid6_d0(struct stripe_head *sh)
  {
  	if (sh->ddf_layout)
  		/* ddf always start from first device */
  		return 0;
  	/* md starts just after Q block */
  	if (sh->qd_idx == sh->disks - 1)
  		return 0;
  	else
  		return sh->qd_idx + 1;
  }
  static inline int raid6_next_disk(int disk, int raid_disks)
  {
  	disk++;
  	return (disk < raid_disks) ? disk : 0;
  }
  
  /* When walking through the disks in a raid5, starting at raid6_d0,
   * We need to map each disk to a 'slot', where the data disks are slot
   * 0 .. raid_disks-3, the parity disk is raid_disks-2 and the Q disk
   * is raid_disks-1.  This help does that mapping.
   */
  static int raid6_idx_to_slot(int idx, struct stripe_head *sh,
  			     int *count, int syndrome_disks)
  {
  	int slot = *count;
  
  	if (sh->ddf_layout)
  		(*count)++;
  	if (idx == sh->pd_idx)
  		return syndrome_disks;
  	if (idx == sh->qd_idx)
  		return syndrome_disks + 1;
  	if (!sh->ddf_layout)
  		(*count)++;
  	return slot;
  }
  
  static void print_raid5_conf (struct r5conf *conf);
  
  static int stripe_operations_active(struct stripe_head *sh)
  {
  	return sh->check_state || sh->reconstruct_state ||
  	       test_bit(STRIPE_BIOFILL_RUN, &sh->state) ||
  	       test_bit(STRIPE_COMPUTE_RUN, &sh->state);
  }
  
  static bool stripe_is_lowprio(struct stripe_head *sh)
  {
  	return (test_bit(STRIPE_R5C_FULL_STRIPE, &sh->state) ||
  		test_bit(STRIPE_R5C_PARTIAL_STRIPE, &sh->state)) &&
  	       !test_bit(STRIPE_R5C_CACHING, &sh->state);
  }
  
  static void raid5_wakeup_stripe_thread(struct stripe_head *sh)
  {
  	struct r5conf *conf = sh->raid_conf;
  	struct r5worker_group *group;
  	int thread_cnt;
  	int i, cpu = sh->cpu;
  
  	if (!cpu_online(cpu)) {
  		cpu = cpumask_any(cpu_online_mask);
  		sh->cpu = cpu;
  	}
  
  	if (list_empty(&sh->lru)) {
  		struct r5worker_group *group;
  		group = conf->worker_groups + cpu_to_group(cpu);
  		if (stripe_is_lowprio(sh))
  			list_add_tail(&sh->lru, &group->loprio_list);
  		else
  			list_add_tail(&sh->lru, &group->handle_list);
  		group->stripes_cnt++;
  		sh->group = group;
  	}
  
  	if (conf->worker_cnt_per_group == 0) {
  		md_wakeup_thread(conf->mddev->thread);
  		return;
  	}
  
  	group = conf->worker_groups + cpu_to_group(sh->cpu);
  
  	group->workers[0].working = true;
  	/* at least one worker should run to avoid race */
  	queue_work_on(sh->cpu, raid5_wq, &group->workers[0].work);
  
  	thread_cnt = group->stripes_cnt / MAX_STRIPE_BATCH - 1;
  	/* wakeup more workers */
  	for (i = 1; i < conf->worker_cnt_per_group && thread_cnt > 0; i++) {
  		if (group->workers[i].working == false) {
  			group->workers[i].working = true;
  			queue_work_on(sh->cpu, raid5_wq,
  				      &group->workers[i].work);
  			thread_cnt--;
  		}
  	}
  }
  
  static void do_release_stripe(struct r5conf *conf, struct stripe_head *sh,
  			      struct list_head *temp_inactive_list)
  {
  	int i;
  	int injournal = 0;	/* number of date pages with R5_InJournal */
  
  	BUG_ON(!list_empty(&sh->lru));
  	BUG_ON(atomic_read(&conf->active_stripes)==0);
  
  	if (r5c_is_writeback(conf->log))
  		for (i = sh->disks; i--; )
  			if (test_bit(R5_InJournal, &sh->dev[i].flags))
  				injournal++;
  	/*
  	 * In the following cases, the stripe cannot be released to cached
  	 * lists. Therefore, we make the stripe write out and set
  	 * STRIPE_HANDLE:
  	 *   1. when quiesce in r5c write back;
  	 *   2. when resync is requested fot the stripe.
  	 */
  	if (test_bit(STRIPE_SYNC_REQUESTED, &sh->state) ||
  	    (conf->quiesce && r5c_is_writeback(conf->log) &&
  	     !test_bit(STRIPE_HANDLE, &sh->state) && injournal != 0)) {
  		if (test_bit(STRIPE_R5C_CACHING, &sh->state))
  			r5c_make_stripe_write_out(sh);
  		set_bit(STRIPE_HANDLE, &sh->state);
  	}
  
  	if (test_bit(STRIPE_HANDLE, &sh->state)) {
  		if (test_bit(STRIPE_DELAYED, &sh->state) &&
  		    !test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
  			list_add_tail(&sh->lru, &conf->delayed_list);
  		else if (test_bit(STRIPE_BIT_DELAY, &sh->state) &&
  			   sh->bm_seq - conf->seq_write > 0)
  			list_add_tail(&sh->lru, &conf->bitmap_list);
  		else {
  			clear_bit(STRIPE_DELAYED, &sh->state);
  			clear_bit(STRIPE_BIT_DELAY, &sh->state);
  			if (conf->worker_cnt_per_group == 0) {
  				if (stripe_is_lowprio(sh))
  					list_add_tail(&sh->lru,
  							&conf->loprio_list);
  				else
  					list_add_tail(&sh->lru,
  							&conf->handle_list);
  			} else {
  				raid5_wakeup_stripe_thread(sh);
  				return;
  			}
  		}
  		md_wakeup_thread(conf->mddev->thread);
  	} else {
  		BUG_ON(stripe_operations_active(sh));
  		if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
  			if (atomic_dec_return(&conf->preread_active_stripes)
  			    < IO_THRESHOLD)
  				md_wakeup_thread(conf->mddev->thread);
  		atomic_dec(&conf->active_stripes);
  		if (!test_bit(STRIPE_EXPANDING, &sh->state)) {
  			if (!r5c_is_writeback(conf->log))
  				list_add_tail(&sh->lru, temp_inactive_list);
  			else {
  				WARN_ON(test_bit(R5_InJournal, &sh->dev[sh->pd_idx].flags));
  				if (injournal == 0)
  					list_add_tail(&sh->lru, temp_inactive_list);
  				else if (injournal == conf->raid_disks - conf->max_degraded) {
  					/* full stripe */
  					if (!test_and_set_bit(STRIPE_R5C_FULL_STRIPE, &sh->state))
  						atomic_inc(&conf->r5c_cached_full_stripes);
  					if (test_and_clear_bit(STRIPE_R5C_PARTIAL_STRIPE, &sh->state))
  						atomic_dec(&conf->r5c_cached_partial_stripes);
  					list_add_tail(&sh->lru, &conf->r5c_full_stripe_list);
  					r5c_check_cached_full_stripe(conf);
  				} else
  					/*
  					 * STRIPE_R5C_PARTIAL_STRIPE is set in
  					 * r5c_try_caching_write(). No need to
  					 * set it again.
  					 */
  					list_add_tail(&sh->lru, &conf->r5c_partial_stripe_list);
  			}
  		}
  	}
  }
  
  static void __release_stripe(struct r5conf *conf, struct stripe_head *sh,
  			     struct list_head *temp_inactive_list)
  {
  	if (atomic_dec_and_test(&sh->count))
  		do_release_stripe(conf, sh, temp_inactive_list);
  }
  
  /*
   * @hash could be NR_STRIPE_HASH_LOCKS, then we have a list of inactive_list
   *
   * Be careful: Only one task can add/delete stripes from temp_inactive_list at
   * given time. Adding stripes only takes device lock, while deleting stripes
   * only takes hash lock.
   */
  static void release_inactive_stripe_list(struct r5conf *conf,
  					 struct list_head *temp_inactive_list,
  					 int hash)
  {
  	int size;
  	bool do_wakeup = false;
  	unsigned long flags;
  
  	if (hash == NR_STRIPE_HASH_LOCKS) {
  		size = NR_STRIPE_HASH_LOCKS;
  		hash = NR_STRIPE_HASH_LOCKS - 1;
  	} else
  		size = 1;
  	while (size) {
  		struct list_head *list = &temp_inactive_list[size - 1];
  
  		/*
  		 * We don't hold any lock here yet, raid5_get_active_stripe() might
  		 * remove stripes from the list
  		 */
  		if (!list_empty_careful(list)) {
  			spin_lock_irqsave(conf->hash_locks + hash, flags);
  			if (list_empty(conf->inactive_list + hash) &&
  			    !list_empty(list))
  				atomic_dec(&conf->empty_inactive_list_nr);
  			list_splice_tail_init(list, conf->inactive_list + hash);
  			do_wakeup = true;
  			spin_unlock_irqrestore(conf->hash_locks + hash, flags);
  		}
  		size--;
  		hash--;
  	}
  
  	if (do_wakeup) {
  		wake_up(&conf->wait_for_stripe);
  		if (atomic_read(&conf->active_stripes) == 0)
  			wake_up(&conf->wait_for_quiescent);
  		if (conf->retry_read_aligned)
  			md_wakeup_thread(conf->mddev->thread);
  	}
  }
  
  /* should hold conf->device_lock already */
  static int release_stripe_list(struct r5conf *conf,
  			       struct list_head *temp_inactive_list)
  {
  	struct stripe_head *sh, *t;
  	int count = 0;
  	struct llist_node *head;
  
  	head = llist_del_all(&conf->released_stripes);
  	head = llist_reverse_order(head);
  	llist_for_each_entry_safe(sh, t, head, release_list) {
  		int hash;
  
  		/* sh could be readded after STRIPE_ON_RELEASE_LIST is cleard */
  		smp_mb();
  		clear_bit(STRIPE_ON_RELEASE_LIST, &sh->state);
  		/*
  		 * Don't worry the bit is set here, because if the bit is set
  		 * again, the count is always > 1. This is true for
  		 * STRIPE_ON_UNPLUG_LIST bit too.
  		 */
  		hash = sh->hash_lock_index;
  		__release_stripe(conf, sh, &temp_inactive_list[hash]);
  		count++;
  	}
  
  	return count;
  }
  
  void raid5_release_stripe(struct stripe_head *sh)
  {
  	struct r5conf *conf = sh->raid_conf;
  	unsigned long flags;
  	struct list_head list;
  	int hash;
  	bool wakeup;
  
  	/* Avoid release_list until the last reference.
  	 */
  	if (atomic_add_unless(&sh->count, -1, 1))
  		return;
  
  	if (unlikely(!conf->mddev->thread) ||
  		test_and_set_bit(STRIPE_ON_RELEASE_LIST, &sh->state))
  		goto slow_path;
  	wakeup = llist_add(&sh->release_list, &conf->released_stripes);
  	if (wakeup)
  		md_wakeup_thread(conf->mddev->thread);
  	return;
  slow_path:
  	/* we are ok here if STRIPE_ON_RELEASE_LIST is set or not */
  	if (atomic_dec_and_lock_irqsave(&sh->count, &conf->device_lock, flags)) {
  		INIT_LIST_HEAD(&list);
  		hash = sh->hash_lock_index;
  		do_release_stripe(conf, sh, &list);
  		spin_unlock_irqrestore(&conf->device_lock, flags);
  		release_inactive_stripe_list(conf, &list, hash);
  	}
  }
  
  static inline void remove_hash(struct stripe_head *sh)
  {
  	pr_debug("remove_hash(), stripe %llu\n",
  		(unsigned long long)sh->sector);
  
  	hlist_del_init(&sh->hash);
  }
  
  static inline void insert_hash(struct r5conf *conf, struct stripe_head *sh)
  {
  	struct hlist_head *hp = stripe_hash(conf, sh->sector);
  
  	pr_debug("insert_hash(), stripe %llu\n",
  		(unsigned long long)sh->sector);
  
  	hlist_add_head(&sh->hash, hp);
  }
  
  /* find an idle stripe, make sure it is unhashed, and return it. */
  static struct stripe_head *get_free_stripe(struct r5conf *conf, int hash)
  {
  	struct stripe_head *sh = NULL;
  	struct list_head *first;
  
  	if (list_empty(conf->inactive_list + hash))
  		goto out;
  	first = (conf->inactive_list + hash)->next;
  	sh = list_entry(first, struct stripe_head, lru);
  	list_del_init(first);
  	remove_hash(sh);
  	atomic_inc(&conf->active_stripes);
  	BUG_ON(hash != sh->hash_lock_index);
  	if (list_empty(conf->inactive_list + hash))
  		atomic_inc(&conf->empty_inactive_list_nr);
  out:
  	return sh;
  }
  
  #if PAGE_SIZE != DEFAULT_STRIPE_SIZE
  static void free_stripe_pages(struct stripe_head *sh)
  {
  	int i;
  	struct page *p;
  
  	/* Have not allocate page pool */
  	if (!sh->pages)
  		return;
  
  	for (i = 0; i < sh->nr_pages; i++) {
  		p = sh->pages[i];
  		if (p)
  			put_page(p);
  		sh->pages[i] = NULL;
  	}
  }
  
  static int alloc_stripe_pages(struct stripe_head *sh, gfp_t gfp)
  {
  	int i;
  	struct page *p;
  
  	for (i = 0; i < sh->nr_pages; i++) {
  		/* The page have allocated. */
  		if (sh->pages[i])
  			continue;
  
  		p = alloc_page(gfp);
  		if (!p) {
  			free_stripe_pages(sh);
  			return -ENOMEM;
  		}
  		sh->pages[i] = p;
  	}
  	return 0;
  }
  
  static int
  init_stripe_shared_pages(struct stripe_head *sh, struct r5conf *conf, int disks)
  {
  	int nr_pages, cnt;
  
  	if (sh->pages)
  		return 0;
  
  	/* Each of the sh->dev[i] need one conf->stripe_size */
  	cnt = PAGE_SIZE / conf->stripe_size;
  	nr_pages = (disks + cnt - 1) / cnt;
  
  	sh->pages = kcalloc(nr_pages, sizeof(struct page *), GFP_KERNEL);
  	if (!sh->pages)
  		return -ENOMEM;
  	sh->nr_pages = nr_pages;
  	sh->stripes_per_page = cnt;
  	return 0;
  }
  #endif
  
  static void shrink_buffers(struct stripe_head *sh)
  {
  	int i;
  	int num = sh->raid_conf->pool_size;
  
  #if PAGE_SIZE == DEFAULT_STRIPE_SIZE
  	for (i = 0; i < num ; i++) {
  		struct page *p;
  
  		WARN_ON(sh->dev[i].page != sh->dev[i].orig_page);
  		p = sh->dev[i].page;
  		if (!p)
  			continue;
  		sh->dev[i].page = NULL;
  		put_page(p);
  	}
  #else
  	for (i = 0; i < num; i++)
  		sh->dev[i].page = NULL;
  	free_stripe_pages(sh); /* Free pages */
  #endif
  }
  
  static int grow_buffers(struct stripe_head *sh, gfp_t gfp)
  {
  	int i;
  	int num = sh->raid_conf->pool_size;
  
  #if PAGE_SIZE == DEFAULT_STRIPE_SIZE
  	for (i = 0; i < num; i++) {
  		struct page *page;
  
  		if (!(page = alloc_page(gfp))) {
  			return 1;
  		}
  		sh->dev[i].page = page;
  		sh->dev[i].orig_page = page;
  		sh->dev[i].offset = 0;
  	}
  #else
  	if (alloc_stripe_pages(sh, gfp))
  		return -ENOMEM;
  
  	for (i = 0; i < num; i++) {
  		sh->dev[i].page = raid5_get_dev_page(sh, i);
  		sh->dev[i].orig_page = sh->dev[i].page;
  		sh->dev[i].offset = raid5_get_page_offset(sh, i);
  	}
  #endif
  	return 0;
  }
  
  static void stripe_set_idx(sector_t stripe, struct r5conf *conf, int previous,
  			    struct stripe_head *sh);
  
  static void init_stripe(struct stripe_head *sh, sector_t sector, int previous)
  {
  	struct r5conf *conf = sh->raid_conf;
  	int i, seq;
  
  	BUG_ON(atomic_read(&sh->count) != 0);
  	BUG_ON(test_bit(STRIPE_HANDLE, &sh->state));
  	BUG_ON(stripe_operations_active(sh));
  	BUG_ON(sh->batch_head);
  
  	pr_debug("init_stripe called, stripe %llu\n",
  		(unsigned long long)sector);
  retry:
  	seq = read_seqcount_begin(&conf->gen_lock);
  	sh->generation = conf->generation - previous;
  	sh->disks = previous ? conf->previous_raid_disks : conf->raid_disks;
  	sh->sector = sector;
  	stripe_set_idx(sector, conf, previous, sh);
  	sh->state = 0;
  
  	for (i = sh->disks; i--; ) {
  		struct r5dev *dev = &sh->dev[i];
  
  		if (dev->toread || dev->read || dev->towrite || dev->written ||
  		    test_bit(R5_LOCKED, &dev->flags)) {
  			pr_err("sector=%llx i=%d %p %p %p %p %d\n",
  			       (unsigned long long)sh->sector, i, dev->toread,
  			       dev->read, dev->towrite, dev->written,
  			       test_bit(R5_LOCKED, &dev->flags));
  			WARN_ON(1);
  		}
  		dev->flags = 0;
  		dev->sector = raid5_compute_blocknr(sh, i, previous);
  	}
  	if (read_seqcount_retry(&conf->gen_lock, seq))
  		goto retry;
  	sh->overwrite_disks = 0;
  	insert_hash(conf, sh);
  	sh->cpu = smp_processor_id();
  	set_bit(STRIPE_BATCH_READY, &sh->state);
  }
  
  static struct stripe_head *__find_stripe(struct r5conf *conf, sector_t sector,
  					 short generation)
  {
  	struct stripe_head *sh;
  
  	pr_debug("__find_stripe, sector %llu\n", (unsigned long long)sector);
  	hlist_for_each_entry(sh, stripe_hash(conf, sector), hash)
  		if (sh->sector == sector && sh->generation == generation)
  			return sh;
  	pr_debug("__stripe %llu not in cache\n", (unsigned long long)sector);
  	return NULL;
  }
  
  /*
   * Need to check if array has failed when deciding whether to:
   *  - start an array
   *  - remove non-faulty devices
   *  - add a spare
   *  - allow a reshape
   * This determination is simple when no reshape is happening.
   * However if there is a reshape, we need to carefully check
   * both the before and after sections.
   * This is because some failed devices may only affect one
   * of the two sections, and some non-in_sync devices may
   * be insync in the section most affected by failed devices.
   */
  int raid5_calc_degraded(struct r5conf *conf)
  {
  	int degraded, degraded2;
  	int i;
  
  	rcu_read_lock();
  	degraded = 0;
  	for (i = 0; i < conf->previous_raid_disks; i++) {
  		struct md_rdev *rdev = rcu_dereference(conf->disks[i].rdev);
  		if (rdev && test_bit(Faulty, &rdev->flags))
  			rdev = rcu_dereference(conf->disks[i].replacement);
  		if (!rdev || test_bit(Faulty, &rdev->flags))
  			degraded++;
  		else if (test_bit(In_sync, &rdev->flags))
  			;
  		else
  			/* not in-sync or faulty.
  			 * If the reshape increases the number of devices,
  			 * this is being recovered by the reshape, so
  			 * this 'previous' section is not in_sync.
  			 * If the number of devices is being reduced however,
  			 * the device can only be part of the array if
  			 * we are reverting a reshape, so this section will
  			 * be in-sync.
  			 */
  			if (conf->raid_disks >= conf->previous_raid_disks)
  				degraded++;
  	}
  	rcu_read_unlock();
  	if (conf->raid_disks == conf->previous_raid_disks)
  		return degraded;
  	rcu_read_lock();
  	degraded2 = 0;
  	for (i = 0; i < conf->raid_disks; i++) {
  		struct md_rdev *rdev = rcu_dereference(conf->disks[i].rdev);
  		if (rdev && test_bit(Faulty, &rdev->flags))
  			rdev = rcu_dereference(conf->disks[i].replacement);
  		if (!rdev || test_bit(Faulty, &rdev->flags))
  			degraded2++;
  		else if (test_bit(In_sync, &rdev->flags))
  			;
  		else
  			/* not in-sync or faulty.
  			 * If reshape increases the number of devices, this
  			 * section has already been recovered, else it
  			 * almost certainly hasn't.
  			 */
  			if (conf->raid_disks <= conf->previous_raid_disks)
  				degraded2++;
  	}
  	rcu_read_unlock();
  	if (degraded2 > degraded)
  		return degraded2;
  	return degraded;
  }
  
  static int has_failed(struct r5conf *conf)
  {
  	int degraded;
  
  	if (conf->mddev->reshape_position == MaxSector)
  		return conf->mddev->degraded > conf->max_degraded;
  
  	degraded = raid5_calc_degraded(conf);
  	if (degraded > conf->max_degraded)
  		return 1;
  	return 0;
  }
  
  struct stripe_head *
  raid5_get_active_stripe(struct r5conf *conf, sector_t sector,
  			int previous, int noblock, int noquiesce)
  {
  	struct stripe_head *sh;
  	int hash = stripe_hash_locks_hash(conf, sector);
  	int inc_empty_inactive_list_flag;
  
  	pr_debug("get_stripe, sector %llu\n", (unsigned long long)sector);
  
  	spin_lock_irq(conf->hash_locks + hash);
  
  	do {
  		wait_event_lock_irq(conf->wait_for_quiescent,
  				    conf->quiesce == 0 || noquiesce,
  				    *(conf->hash_locks + hash));
  		sh = __find_stripe(conf, sector, conf->generation - previous);
  		if (!sh) {
  			if (!test_bit(R5_INACTIVE_BLOCKED, &conf->cache_state)) {
  				sh = get_free_stripe(conf, hash);
  				if (!sh && !test_bit(R5_DID_ALLOC,
  						     &conf->cache_state))
  					set_bit(R5_ALLOC_MORE,
  						&conf->cache_state);
  			}
  			if (noblock && sh == NULL)
  				break;
  
  			r5c_check_stripe_cache_usage(conf);
  			if (!sh) {
  				set_bit(R5_INACTIVE_BLOCKED,
  					&conf->cache_state);
  				r5l_wake_reclaim(conf->log, 0);
  				wait_event_lock_irq(
  					conf->wait_for_stripe,
  					!list_empty(conf->inactive_list + hash) &&
  					(atomic_read(&conf->active_stripes)
  					 < (conf->max_nr_stripes * 3 / 4)
  					 || !test_bit(R5_INACTIVE_BLOCKED,
  						      &conf->cache_state)),
  					*(conf->hash_locks + hash));
  				clear_bit(R5_INACTIVE_BLOCKED,
  					  &conf->cache_state);
  			} else {
  				init_stripe(sh, sector, previous);
  				atomic_inc(&sh->count);
  			}
  		} else if (!atomic_inc_not_zero(&sh->count)) {
  			spin_lock(&conf->device_lock);
  			if (!atomic_read(&sh->count)) {
  				if (!test_bit(STRIPE_HANDLE, &sh->state))
  					atomic_inc(&conf->active_stripes);
  				BUG_ON(list_empty(&sh->lru) &&
  				       !test_bit(STRIPE_EXPANDING, &sh->state));
  				inc_empty_inactive_list_flag = 0;
  				if (!list_empty(conf->inactive_list + hash))
  					inc_empty_inactive_list_flag = 1;
  				list_del_init(&sh->lru);
  				if (list_empty(conf->inactive_list + hash) && inc_empty_inactive_list_flag)
  					atomic_inc(&conf->empty_inactive_list_nr);
  				if (sh->group) {
  					sh->group->stripes_cnt--;
  					sh->group = NULL;
  				}
  			}
  			atomic_inc(&sh->count);
  			spin_unlock(&conf->device_lock);
  		}
  	} while (sh == NULL);
  
  	spin_unlock_irq(conf->hash_locks + hash);
  	return sh;
  }
  
  static bool is_full_stripe_write(struct stripe_head *sh)
  {
  	BUG_ON(sh->overwrite_disks > (sh->disks - sh->raid_conf->max_degraded));
  	return sh->overwrite_disks == (sh->disks - sh->raid_conf->max_degraded);
  }
  
  static void lock_two_stripes(struct stripe_head *sh1, struct stripe_head *sh2)
  		__acquires(&sh1->stripe_lock)
  		__acquires(&sh2->stripe_lock)
  {
  	if (sh1 > sh2) {
  		spin_lock_irq(&sh2->stripe_lock);
  		spin_lock_nested(&sh1->stripe_lock, 1);
  	} else {
  		spin_lock_irq(&sh1->stripe_lock);
  		spin_lock_nested(&sh2->stripe_lock, 1);
  	}
  }
  
  static void unlock_two_stripes(struct stripe_head *sh1, struct stripe_head *sh2)
  		__releases(&sh1->stripe_lock)
  		__releases(&sh2->stripe_lock)
  {
  	spin_unlock(&sh1->stripe_lock);
  	spin_unlock_irq(&sh2->stripe_lock);
  }
  
  /* Only freshly new full stripe normal write stripe can be added to a batch list */
  static bool stripe_can_batch(struct stripe_head *sh)
  {
  	struct r5conf *conf = sh->raid_conf;
  
  	if (raid5_has_log(conf) || raid5_has_ppl(conf))
  		return false;
  	return test_bit(STRIPE_BATCH_READY, &sh->state) &&
  		!test_bit(STRIPE_BITMAP_PENDING, &sh->state) &&
  		is_full_stripe_write(sh);
  }
  
  /* we only do back search */
  static void stripe_add_to_batch_list(struct r5conf *conf, struct stripe_head *sh)
  {
  	struct stripe_head *head;
  	sector_t head_sector, tmp_sec;
  	int hash;
  	int dd_idx;
  	int inc_empty_inactive_list_flag;
  
  	/* Don't cross chunks, so stripe pd_idx/qd_idx is the same */
  	tmp_sec = sh->sector;
  	if (!sector_div(tmp_sec, conf->chunk_sectors))
  		return;
  	head_sector = sh->sector - RAID5_STRIPE_SECTORS(conf);
  
  	hash = stripe_hash_locks_hash(conf, head_sector);
  	spin_lock_irq(conf->hash_locks + hash);
  	head = __find_stripe(conf, head_sector, conf->generation);
  	if (head && !atomic_inc_not_zero(&head->count)) {
  		spin_lock(&conf->device_lock);
  		if (!atomic_read(&head->count)) {
  			if (!test_bit(STRIPE_HANDLE, &head->state))
  				atomic_inc(&conf->active_stripes);
  			BUG_ON(list_empty(&head->lru) &&
  			       !test_bit(STRIPE_EXPANDING, &head->state));
  			inc_empty_inactive_list_flag = 0;
  			if (!list_empty(conf->inactive_list + hash))
  				inc_empty_inactive_list_flag = 1;
  			list_del_init(&head->lru);
  			if (list_empty(conf->inactive_list + hash) && inc_empty_inactive_list_flag)
  				atomic_inc(&conf->empty_inactive_list_nr);
  			if (head->group) {
  				head->group->stripes_cnt--;
  				head->group = NULL;
  			}
  		}
  		atomic_inc(&head->count);
  		spin_unlock(&conf->device_lock);
  	}
  	spin_unlock_irq(conf->hash_locks + hash);
  
  	if (!head)
  		return;
  	if (!stripe_can_batch(head))
  		goto out;
  
  	lock_two_stripes(head, sh);
  	/* clear_batch_ready clear the flag */
  	if (!stripe_can_batch(head) || !stripe_can_batch(sh))
  		goto unlock_out;
  
  	if (sh->batch_head)
  		goto unlock_out;
  
  	dd_idx = 0;
  	while (dd_idx == sh->pd_idx || dd_idx == sh->qd_idx)
  		dd_idx++;
  	if (head->dev[dd_idx].towrite->bi_opf != sh->dev[dd_idx].towrite->bi_opf ||
  	    bio_op(head->dev[dd_idx].towrite) != bio_op(sh->dev[dd_idx].towrite))
  		goto unlock_out;
  
  	if (head->batch_head) {
  		spin_lock(&head->batch_head->batch_lock);
  		/* This batch list is already running */
  		if (!stripe_can_batch(head)) {
  			spin_unlock(&head->batch_head->batch_lock);
  			goto unlock_out;
  		}
  		/*
  		 * We must assign batch_head of this stripe within the
  		 * batch_lock, otherwise clear_batch_ready of batch head
  		 * stripe could clear BATCH_READY bit of this stripe and
  		 * this stripe->batch_head doesn't get assigned, which
  		 * could confuse clear_batch_ready for this stripe
  		 */
  		sh->batch_head = head->batch_head;
  
  		/*
  		 * at this point, head's BATCH_READY could be cleared, but we
  		 * can still add the stripe to batch list
  		 */
  		list_add(&sh->batch_list, &head->batch_list);
  		spin_unlock(&head->batch_head->batch_lock);
  	} else {
  		head->batch_head = head;
  		sh->batch_head = head->batch_head;
  		spin_lock(&head->batch_lock);
  		list_add_tail(&sh->batch_list, &head->batch_list);
  		spin_unlock(&head->batch_lock);
  	}
  
  	if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
  		if (atomic_dec_return(&conf->preread_active_stripes)
  		    < IO_THRESHOLD)
  			md_wakeup_thread(conf->mddev->thread);
  
  	if (test_and_clear_bit(STRIPE_BIT_DELAY, &sh->state)) {
  		int seq = sh->bm_seq;
  		if (test_bit(STRIPE_BIT_DELAY, &sh->batch_head->state) &&
  		    sh->batch_head->bm_seq > seq)
  			seq = sh->batch_head->bm_seq;
  		set_bit(STRIPE_BIT_DELAY, &sh->batch_head->state);
  		sh->batch_head->bm_seq = seq;
  	}
  
  	atomic_inc(&sh->count);
  unlock_out:
  	unlock_two_stripes(head, sh);
  out:
  	raid5_release_stripe(head);
  }
  
  /* Determine if 'data_offset' or 'new_data_offset' should be used
   * in this stripe_head.
   */
  static int use_new_offset(struct r5conf *conf, struct stripe_head *sh)
  {
  	sector_t progress = conf->reshape_progress;
  	/* Need a memory barrier to make sure we see the value
  	 * of conf->generation, or ->data_offset that was set before
  	 * reshape_progress was updated.
  	 */
  	smp_rmb();
  	if (progress == MaxSector)
  		return 0;
  	if (sh->generation == conf->generation - 1)
  		return 0;
  	/* We are in a reshape, and this is a new-generation stripe,
  	 * so use new_data_offset.
  	 */
  	return 1;
  }
  
  static void dispatch_bio_list(struct bio_list *tmp)
  {
  	struct bio *bio;
  
  	while ((bio = bio_list_pop(tmp)))
  		submit_bio_noacct(bio);
  }
  
  static int cmp_stripe(void *priv, const struct list_head *a,
  		      const struct list_head *b)
  {
  	const struct r5pending_data *da = list_entry(a,
  				struct r5pending_data, sibling);
  	const struct r5pending_data *db = list_entry(b,
  				struct r5pending_data, sibling);
  	if (da->sector > db->sector)
  		return 1;
  	if (da->sector < db->sector)
  		return -1;
  	return 0;
  }
  
  static void dispatch_defer_bios(struct r5conf *conf, int target,
  				struct bio_list *list)
  {
  	struct r5pending_data *data;
  	struct list_head *first, *next = NULL;
  	int cnt = 0;
  
  	if (conf->pending_data_cnt == 0)
  		return;
  
  	list_sort(NULL, &conf->pending_list, cmp_stripe);
  
  	first = conf->pending_list.next;
  
  	/* temporarily move the head */
  	if (conf->next_pending_data)
  		list_move_tail(&conf->pending_list,
  				&conf->next_pending_data->sibling);
  
  	while (!list_empty(&conf->pending_list)) {
  		data = list_first_entry(&conf->pending_list,
  			struct r5pending_data, sibling);
  		if (&data->sibling == first)
  			first = data->sibling.next;
  		next = data->sibling.next;
  
  		bio_list_merge(list, &data->bios);
  		list_move(&data->sibling, &conf->free_list);
  		cnt++;
  		if (cnt >= target)
  			break;
  	}
  	conf->pending_data_cnt -= cnt;
  	BUG_ON(conf->pending_data_cnt < 0 || cnt < target);
  
  	if (next != &conf->pending_list)
  		conf->next_pending_data = list_entry(next,
  				struct r5pending_data, sibling);
  	else
  		conf->next_pending_data = NULL;
  	/* list isn't empty */
  	if (first != &conf->pending_list)
  		list_move_tail(&conf->pending_list, first);
  }
  
  static void flush_deferred_bios(struct r5conf *conf)
  {
  	struct bio_list tmp = BIO_EMPTY_LIST;
  
  	if (conf->pending_data_cnt == 0)
  		return;
  
  	spin_lock(&conf->pending_bios_lock);
  	dispatch_defer_bios(conf, conf->pending_data_cnt, &tmp);
  	BUG_ON(conf->pending_data_cnt != 0);
  	spin_unlock(&conf->pending_bios_lock);
  
  	dispatch_bio_list(&tmp);
  }
  
  static void defer_issue_bios(struct r5conf *conf, sector_t sector,
  				struct bio_list *bios)
  {
  	struct bio_list tmp = BIO_EMPTY_LIST;
  	struct r5pending_data *ent;
  
  	spin_lock(&conf->pending_bios_lock);
  	ent = list_first_entry(&conf->free_list, struct r5pending_data,
  							sibling);
  	list_move_tail(&ent->sibling, &conf->pending_list);
  	ent->sector = sector;
  	bio_list_init(&ent->bios);
  	bio_list_merge(&ent->bios, bios);
  	conf->pending_data_cnt++;
  	if (conf->pending_data_cnt >= PENDING_IO_MAX)
  		dispatch_defer_bios(conf, PENDING_IO_ONE_FLUSH, &tmp);
  
  	spin_unlock(&conf->pending_bios_lock);
  
  	dispatch_bio_list(&tmp);
  }
  
  static void
  raid5_end_read_request(struct bio *bi);
  static void
  raid5_end_write_request(struct bio *bi);
  
  static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
  {
  	struct r5conf *conf = sh->raid_conf;
  	int i, disks = sh->disks;
  	struct stripe_head *head_sh = sh;
  	struct bio_list pending_bios = BIO_EMPTY_LIST;
  	bool should_defer;
  
  	might_sleep();
  
  	if (log_stripe(sh, s) == 0)
  		return;
  
  	should_defer = conf->batch_bio_dispatch && conf->group_cnt;
  
  	for (i = disks; i--; ) {
  		int op, op_flags = 0;
  		int replace_only = 0;
  		struct bio *bi, *rbi;
  		struct md_rdev *rdev, *rrdev = NULL;
  
  		sh = head_sh;
  		if (test_and_clear_bit(R5_Wantwrite, &sh->dev[i].flags)) {
  			op = REQ_OP_WRITE;
  			if (test_and_clear_bit(R5_WantFUA, &sh->dev[i].flags))
  				op_flags = REQ_FUA;
  			if (test_bit(R5_Discard, &sh->dev[i].flags))
  				op = REQ_OP_DISCARD;
  		} else if (test_and_clear_bit(R5_Wantread, &sh->dev[i].flags))
  			op = REQ_OP_READ;
  		else if (test_and_clear_bit(R5_WantReplace,
  					    &sh->dev[i].flags)) {
  			op = REQ_OP_WRITE;
  			replace_only = 1;
  		} else
  			continue;
  		if (test_and_clear_bit(R5_SyncIO, &sh->dev[i].flags))
  			op_flags |= REQ_SYNC;
  
  again:
  		bi = &sh->dev[i].req;
  		rbi = &sh->dev[i].rreq; /* For writing to replacement */
  
  		rcu_read_lock();
  		rrdev = rcu_dereference(conf->disks[i].replacement);
  		smp_mb(); /* Ensure that if rrdev is NULL, rdev won't be */
  		rdev = rcu_dereference(conf->disks[i].rdev);
  		if (!rdev) {
  			rdev = rrdev;
  			rrdev = NULL;
  		}
  		if (op_is_write(op)) {
  			if (replace_only)
  				rdev = NULL;
  			if (rdev == rrdev)
  				/* We raced and saw duplicates */
  				rrdev = NULL;
  		} else {
  			if (test_bit(R5_ReadRepl, &head_sh->dev[i].flags) && rrdev)
  				rdev = rrdev;
  			rrdev = NULL;
  		}
  
  		if (rdev && test_bit(Faulty, &rdev->flags))
  			rdev = NULL;
  		if (rdev)
  			atomic_inc(&rdev->nr_pending);
  		if (rrdev && test_bit(Faulty, &rrdev->flags))
  			rrdev = NULL;
  		if (rrdev)
  			atomic_inc(&rrdev->nr_pending);
  		rcu_read_unlock();
  
  		/* We have already checked bad blocks for reads.  Now
  		 * need to check for writes.  We never accept write errors
  		 * on the replacement, so we don't to check rrdev.
  		 */
  		while (op_is_write(op) && rdev &&
  		       test_bit(WriteErrorSeen, &rdev->flags)) {
  			sector_t first_bad;
  			int bad_sectors;
  			int bad = is_badblock(rdev, sh->sector, RAID5_STRIPE_SECTORS(conf),
  					      &first_bad, &bad_sectors);
  			if (!bad)
  				break;
  
  			if (bad < 0) {
  				set_bit(BlockedBadBlocks, &rdev->flags);
  				if (!conf->mddev->external &&
  				    conf->mddev->sb_flags) {
  					/* It is very unlikely, but we might
  					 * still need to write out the
  					 * bad block log - better give it
  					 * a chance*/
  					md_check_recovery(conf->mddev);
  				}
  				/*
  				 * Because md_wait_for_blocked_rdev
  				 * will dec nr_pending, we must
  				 * increment it first.
  				 */
  				atomic_inc(&rdev->nr_pending);
  				md_wait_for_blocked_rdev(rdev, conf->mddev);
  			} else {
  				/* Acknowledged bad block - skip the write */
  				rdev_dec_pending(rdev, conf->mddev);
  				rdev = NULL;
  			}
  		}
  
  		if (rdev) {
  			if (s->syncing || s->expanding || s->expanded
  			    || s->replacing)
  				md_sync_acct(rdev->bdev, RAID5_STRIPE_SECTORS(conf));
  
  			set_bit(STRIPE_IO_STARTED, &sh->state);
  
  			bio_set_dev(bi, rdev->bdev);
  			bio_set_op_attrs(bi, op, op_flags);
  			bi->bi_end_io = op_is_write(op)
  				? raid5_end_write_request
  				: raid5_end_read_request;
  			bi->bi_private = sh;
  
  			pr_debug("%s: for %llu schedule op %d on disc %d\n",
  				__func__, (unsigned long long)sh->sector,
  				bi->bi_opf, i);
  			atomic_inc(&sh->count);
  			if (sh != head_sh)
  				atomic_inc(&head_sh->count);
  			if (use_new_offset(conf, sh))
  				bi->bi_iter.bi_sector = (sh->sector
  						 + rdev->new_data_offset);
  			else
  				bi->bi_iter.bi_sector = (sh->sector
  						 + rdev->data_offset);
  			if (test_bit(R5_ReadNoMerge, &head_sh->dev[i].flags))
  				bi->bi_opf |= REQ_NOMERGE;
  
  			if (test_bit(R5_SkipCopy, &sh->dev[i].flags))
  				WARN_ON(test_bit(R5_UPTODATE, &sh->dev[i].flags));
  
  			if (!op_is_write(op) &&
  			    test_bit(R5_InJournal, &sh->dev[i].flags))
  				/*
  				 * issuing read for a page in journal, this
  				 * must be preparing for prexor in rmw; read
  				 * the data into orig_page
  				 */
  				sh->dev[i].vec.bv_page = sh->dev[i].orig_page;
  			else
  				sh->dev[i].vec.bv_page = sh->dev[i].page;
  			bi->bi_vcnt = 1;
  			bi->bi_io_vec[0].bv_len = RAID5_STRIPE_SIZE(conf);
  			bi->bi_io_vec[0].bv_offset = sh->dev[i].offset;
  			bi->bi_iter.bi_size = RAID5_STRIPE_SIZE(conf);
  			bi->bi_write_hint = sh->dev[i].write_hint;
  			if (!rrdev)
  				sh->dev[i].write_hint = RWH_WRITE_LIFE_NOT_SET;
  			/*
  			 * If this is discard request, set bi_vcnt 0. We don't
  			 * want to confuse SCSI because SCSI will replace payload
  			 */
  			if (op == REQ_OP_DISCARD)
  				bi->bi_vcnt = 0;
  			if (rrdev)
  				set_bit(R5_DOUBLE_LOCKED, &sh->dev[i].flags);
  
  			if (conf->mddev->gendisk)
  				trace_block_bio_remap(bi->bi_disk->queue,
  						      bi, disk_devt(conf->mddev->gendisk),
  						      sh->dev[i].sector);
  			if (should_defer && op_is_write(op))
  				bio_list_add(&pending_bios, bi);
  			else
  				submit_bio_noacct(bi);
  		}
  		if (rrdev) {
  			if (s->syncing || s->expanding || s->expanded
  			    || s->replacing)
  				md_sync_acct(rrdev->bdev, RAID5_STRIPE_SECTORS(conf));
  
  			set_bit(STRIPE_IO_STARTED, &sh->state);
  
  			bio_set_dev(rbi, rrdev->bdev);
  			bio_set_op_attrs(rbi, op, op_flags);
  			BUG_ON(!op_is_write(op));
  			rbi->bi_end_io = raid5_end_write_request;
  			rbi->bi_private = sh;
  
  			pr_debug("%s: for %llu schedule op %d on "
  				 "replacement disc %d\n",
  				__func__, (unsigned long long)sh->sector,
  				rbi->bi_opf, i);
  			atomic_inc(&sh->count);
  			if (sh != head_sh)
  				atomic_inc(&head_sh->count);
  			if (use_new_offset(conf, sh))
  				rbi->bi_iter.bi_sector = (sh->sector
  						  + rrdev->new_data_offset);
  			else
  				rbi->bi_iter.bi_sector = (sh->sector
  						  + rrdev->data_offset);
  			if (test_bit(R5_SkipCopy, &sh->dev[i].flags))
  				WARN_ON(test_bit(R5_UPTODATE, &sh->dev[i].flags));
  			sh->dev[i].rvec.bv_page = sh->dev[i].page;
  			rbi->bi_vcnt = 1;
  			rbi->bi_io_vec[0].bv_len = RAID5_STRIPE_SIZE(conf);
  			rbi->bi_io_vec[0].bv_offset = sh->dev[i].offset;
  			rbi->bi_iter.bi_size = RAID5_STRIPE_SIZE(conf);
  			rbi->bi_write_hint = sh->dev[i].write_hint;
  			sh->dev[i].write_hint = RWH_WRITE_LIFE_NOT_SET;
  			/*
  			 * If this is discard request, set bi_vcnt 0. We don't
  			 * want to confuse SCSI because SCSI will replace payload
  			 */
  			if (op == REQ_OP_DISCARD)
  				rbi->bi_vcnt = 0;
  			if (conf->mddev->gendisk)
  				trace_block_bio_remap(rbi->bi_disk->queue,
  						      rbi, disk_devt(conf->mddev->gendisk),
  						      sh->dev[i].sector);
  			if (should_defer && op_is_write(op))
  				bio_list_add(&pending_bios, rbi);
  			else
  				submit_bio_noacct(rbi);
  		}
  		if (!rdev && !rrdev) {
  			if (op_is_write(op))
  				set_bit(STRIPE_DEGRADED, &sh->state);
  			pr_debug("skip op %d on disc %d for sector %llu\n",
  				bi->bi_opf, i, (unsigned long long)sh->sector);
  			clear_bit(R5_LOCKED, &sh->dev[i].flags);
  			set_bit(STRIPE_HANDLE, &sh->state);
  		}
  
  		if (!head_sh->batch_head)
  			continue;
  		sh = list_first_entry(&sh->batch_list, struct stripe_head,
  				      batch_list);
  		if (sh != head_sh)
  			goto again;
  	}
  
  	if (should_defer && !bio_list_empty(&pending_bios))
  		defer_issue_bios(conf, head_sh->sector, &pending_bios);
  }
  
  static struct dma_async_tx_descriptor *
  async_copy_data(int frombio, struct bio *bio, struct page **page,
  	unsigned int poff, sector_t sector, struct dma_async_tx_descriptor *tx,
  	struct stripe_head *sh, int no_skipcopy)
  {
  	struct bio_vec bvl;
  	struct bvec_iter iter;
  	struct page *bio_page;
  	int page_offset;
  	struct async_submit_ctl submit;
  	enum async_tx_flags flags = 0;
  	struct r5conf *conf = sh->raid_conf;
  
  	if (bio->bi_iter.bi_sector >= sector)
  		page_offset = (signed)(bio->bi_iter.bi_sector - sector) * 512;
  	else
  		page_offset = (signed)(sector - bio->bi_iter.bi_sector) * -512;
  
  	if (frombio)
  		flags |= ASYNC_TX_FENCE;
  	init_async_submit(&submit, flags, tx, NULL, NULL, NULL);
  
  	bio_for_each_segment(bvl, bio, iter) {
  		int len = bvl.bv_len;
  		int clen;
  		int b_offset = 0;
  
  		if (page_offset < 0) {
  			b_offset = -page_offset;
  			page_offset += b_offset;
  			len -= b_offset;
  		}
  
  		if (len > 0 && page_offset + len > RAID5_STRIPE_SIZE(conf))
  			clen = RAID5_STRIPE_SIZE(conf) - page_offset;
  		else
  			clen = len;
  
  		if (clen > 0) {
  			b_offset += bvl.bv_offset;
  			bio_page = bvl.bv_page;
  			if (frombio) {
  				if (conf->skip_copy &&
  				    b_offset == 0 && page_offset == 0 &&
  				    clen == RAID5_STRIPE_SIZE(conf) &&
  				    !no_skipcopy)
  					*page = bio_page;
  				else
  					tx = async_memcpy(*page, bio_page, page_offset + poff,
  						  b_offset, clen, &submit);
  			} else
  				tx = async_memcpy(bio_page, *page, b_offset,
  						  page_offset + poff, clen, &submit);
  		}
  		/* chain the operations */
  		submit.depend_tx = tx;
  
  		if (clen < len) /* hit end of page */
  			break;
  		page_offset +=  len;
  	}
  
  	return tx;
  }
  
  static void ops_complete_biofill(void *stripe_head_ref)
  {
  	struct stripe_head *sh = stripe_head_ref;
  	int i;
  	struct r5conf *conf = sh->raid_conf;
  
  	pr_debug("%s: stripe %llu\n", __func__,
  		(unsigned long long)sh->sector);
  
  	/* clear completed biofills */
  	for (i = sh->disks; i--; ) {
  		struct r5dev *dev = &sh->dev[i];
  
  		/* acknowledge completion of a biofill operation */
  		/* and check if we need to reply to a read request,
  		 * new R5_Wantfill requests are held off until
  		 * !STRIPE_BIOFILL_RUN
  		 */
  		if (test_and_clear_bit(R5_Wantfill, &dev->flags)) {
  			struct bio *rbi, *rbi2;
  
  			BUG_ON(!dev->read);
  			rbi = dev->read;
  			dev->read = NULL;
  			while (rbi && rbi->bi_iter.bi_sector <
  				dev->sector + RAID5_STRIPE_SECTORS(conf)) {
  				rbi2 = r5_next_bio(conf, rbi, dev->sector);
  				bio_endio(rbi);
  				rbi = rbi2;
  			}
  		}
  	}
  	clear_bit(STRIPE_BIOFILL_RUN, &sh->state);
  
  	set_bit(STRIPE_HANDLE, &sh->state);
  	raid5_release_stripe(sh);
  }
  
  static void ops_run_biofill(struct stripe_head *sh)
  {
  	struct dma_async_tx_descriptor *tx = NULL;
  	struct async_submit_ctl submit;
  	int i;
  	struct r5conf *conf = sh->raid_conf;
  
  	BUG_ON(sh->batch_head);
  	pr_debug("%s: stripe %llu\n", __func__,
  		(unsigned long long)sh->sector);
  
  	for (i = sh->disks; i--; ) {
  		struct r5dev *dev = &sh->dev[i];
  		if (test_bit(R5_Wantfill, &dev->flags)) {
  			struct bio *rbi;
  			spin_lock_irq(&sh->stripe_lock);
  			dev->read = rbi = dev->toread;
  			dev->toread = NULL;
  			spin_unlock_irq(&sh->stripe_lock);
  			while (rbi && rbi->bi_iter.bi_sector <
  				dev->sector + RAID5_STRIPE_SECTORS(conf)) {
  				tx = async_copy_data(0, rbi, &dev->page,
  						     dev->offset,
  						     dev->sector, tx, sh, 0);
  				rbi = r5_next_bio(conf, rbi, dev->sector);
  			}
  		}
  	}
  
  	atomic_inc(&sh->count);
  	init_async_submit(&submit, ASYNC_TX_ACK, tx, ops_complete_biofill, sh, NULL);
  	async_trigger_callback(&submit);
  }
  
  static void mark_target_uptodate(struct stripe_head *sh, int target)
  {
  	struct r5dev *tgt;
  
  	if (target < 0)
  		return;
  
  	tgt = &sh->dev[target];
  	set_bit(R5_UPTODATE, &tgt->flags);
  	BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
  	clear_bit(R5_Wantcompute, &tgt->flags);
  }
  
  static void ops_complete_compute(void *stripe_head_ref)
  {
  	struct stripe_head *sh = stripe_head_ref;
  
  	pr_debug("%s: stripe %llu\n", __func__,
  		(unsigned long long)sh->sector);
  
  	/* mark the computed target(s) as uptodate */
  	mark_target_uptodate(sh, sh->ops.target);
  	mark_target_uptodate(sh, sh->ops.target2);
  
  	clear_bit(STRIPE_COMPUTE_RUN, &sh->state);
  	if (sh->check_state == check_state_compute_run)
  		sh->check_state = check_state_compute_result;
  	set_bit(STRIPE_HANDLE, &sh->state);
  	raid5_release_stripe(sh);
  }
  
  /* return a pointer to the address conversion region of the scribble buffer */
  static struct page **to_addr_page(struct raid5_percpu *percpu, int i)
  {
  	return percpu->scribble + i * percpu->scribble_obj_size;
  }
  
  /* return a pointer to the address conversion region of the scribble buffer */
  static addr_conv_t *to_addr_conv(struct stripe_head *sh,
  				 struct raid5_percpu *percpu, int i)
  {
  	return (void *) (to_addr_page(percpu, i) + sh->disks + 2);
  }
  
  /*
   * Return a pointer to record offset address.
   */
  static unsigned int *
  to_addr_offs(struct stripe_head *sh, struct raid5_percpu *percpu)
  {
  	return (unsigned int *) (to_addr_conv(sh, percpu, 0) + sh->disks + 2);
  }
  
  static struct dma_async_tx_descriptor *
  ops_run_compute5(struct stripe_head *sh, struct raid5_percpu *percpu)
  {
  	int disks = sh->disks;
  	struct page **xor_srcs = to_addr_page(percpu, 0);
  	unsigned int *off_srcs = to_addr_offs(sh, percpu);
  	int target = sh->ops.target;
  	struct r5dev *tgt = &sh->dev[target];
  	struct page *xor_dest = tgt->page;
  	unsigned int off_dest = tgt->offset;
  	int count = 0;
  	struct dma_async_tx_descriptor *tx;
  	struct async_submit_ctl submit;
  	int i;
  
  	BUG_ON(sh->batch_head);
  
  	pr_debug("%s: stripe %llu block: %d\n",
  		__func__, (unsigned long long)sh->sector, target);
  	BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
  
  	for (i = disks; i--; ) {
  		if (i != target) {
  			off_srcs[count] = sh->dev[i].offset;
  			xor_srcs[count++] = sh->dev[i].page;
  		}
  	}
  
  	atomic_inc(&sh->count);
  
  	init_async_submit(&submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_ZERO_DST, NULL,
  			  ops_complete_compute, sh, to_addr_conv(sh, percpu, 0));
  	if (unlikely(count == 1))
  		tx = async_memcpy(xor_dest, xor_srcs[0], off_dest, off_srcs[0],
  				RAID5_STRIPE_SIZE(sh->raid_conf), &submit);
  	else
  		tx = async_xor_offs(xor_dest, off_dest, xor_srcs, off_srcs, count,
  				RAID5_STRIPE_SIZE(sh->raid_conf), &submit);
  
  	return tx;
  }
  
  /* set_syndrome_sources - populate source buffers for gen_syndrome
   * @srcs - (struct page *) array of size sh->disks
   * @offs - (unsigned int) array of offset for each page
   * @sh - stripe_head to parse
   *
   * Populates srcs in proper layout order for the stripe and returns the
   * 'count' of sources to be used in a call to async_gen_syndrome.  The P
   * destination buffer is recorded in srcs[count] and the Q destination
   * is recorded in srcs[count+1]].
   */
  static int set_syndrome_sources(struct page **srcs,
  				unsigned int *offs,
  				struct stripe_head *sh,
  				int srctype)
  {
  	int disks = sh->disks;
  	int syndrome_disks = sh->ddf_layout ? disks : (disks - 2);
  	int d0_idx = raid6_d0(sh);
  	int count;
  	int i;
  
  	for (i = 0; i < disks; i++)
  		srcs[i] = NULL;
  
  	count = 0;
  	i = d0_idx;
  	do {
  		int slot = raid6_idx_to_slot(i, sh, &count, syndrome_disks);
  		struct r5dev *dev = &sh->dev[i];
  
  		if (i == sh->qd_idx || i == sh->pd_idx ||
  		    (srctype == SYNDROME_SRC_ALL) ||
  		    (srctype == SYNDROME_SRC_WANT_DRAIN &&
  		     (test_bit(R5_Wantdrain, &dev->flags) ||
  		      test_bit(R5_InJournal, &dev->flags))) ||
  		    (srctype == SYNDROME_SRC_WRITTEN &&
  		     (dev->written ||
  		      test_bit(R5_InJournal, &dev->flags)))) {
  			if (test_bit(R5_InJournal, &dev->flags))
  				srcs[slot] = sh->dev[i].orig_page;
  			else
  				srcs[slot] = sh->dev[i].page;
  			/*
  			 * For R5_InJournal, PAGE_SIZE must be 4KB and will
  			 * not shared page. In that case, dev[i].offset
  			 * is 0.
  			 */
  			offs[slot] = sh->dev[i].offset;
  		}
  		i = raid6_next_disk(i, disks);
  	} while (i != d0_idx);
  
  	return syndrome_disks;
  }
  
  static struct dma_async_tx_descriptor *
  ops_run_compute6_1(struct stripe_head *sh, struct raid5_percpu *percpu)
  {
  	int disks = sh->disks;
  	struct page **blocks = to_addr_page(percpu, 0);
  	unsigned int *offs = to_addr_offs(sh, percpu);
  	int target;
  	int qd_idx = sh->qd_idx;
  	struct dma_async_tx_descriptor *tx;
  	struct async_submit_ctl submit;
  	struct r5dev *tgt;
  	struct page *dest;
  	unsigned int dest_off;
  	int i;
  	int count;
  
  	BUG_ON(sh->batch_head);
  	if (sh->ops.target < 0)
  		target = sh->ops.target2;
  	else if (sh->ops.target2 < 0)
  		target = sh->ops.target;
  	else
  		/* we should only have one valid target */
  		BUG();
  	BUG_ON(target < 0);
  	pr_debug("%s: stripe %llu block: %d\n",
  		__func__, (unsigned long long)sh->sector, target);
  
  	tgt = &sh->dev[target];
  	BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
  	dest = tgt->page;
  	dest_off = tgt->offset;
  
  	atomic_inc(&sh->count);
  
  	if (target == qd_idx) {
  		count = set_syndrome_sources(blocks, offs, sh, SYNDROME_SRC_ALL);
  		blocks[count] = NULL; /* regenerating p is not necessary */
  		BUG_ON(blocks[count+1] != dest); /* q should already be set */
  		init_async_submit(&submit, ASYNC_TX_FENCE, NULL,
  				  ops_complete_compute, sh,
  				  to_addr_conv(sh, percpu, 0));
  		tx = async_gen_syndrome(blocks, offs, count+2,
  				RAID5_STRIPE_SIZE(sh->raid_conf), &submit);
  	} else {
  		/* Compute any data- or p-drive using XOR */
  		count = 0;
  		for (i = disks; i-- ; ) {
  			if (i == target || i == qd_idx)
  				continue;
  			offs[count] = sh->dev[i].offset;
  			blocks[count++] = sh->dev[i].page;
  		}
  
  		init_async_submit(&submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_ZERO_DST,
  				  NULL, ops_complete_compute, sh,
  				  to_addr_conv(sh, percpu, 0));
  		tx = async_xor_offs(dest, dest_off, blocks, offs, count,
  				RAID5_STRIPE_SIZE(sh->raid_conf), &submit);
  	}
  
  	return tx;
  }
  
  static struct dma_async_tx_descriptor *
  ops_run_compute6_2(struct stripe_head *sh, struct raid5_percpu *percpu)
  {
  	int i, count, disks = sh->disks;
  	int syndrome_disks = sh->ddf_layout ? disks : disks-2;
  	int d0_idx = raid6_d0(sh);
  	int faila = -1, failb = -1;
  	int target = sh->ops.target;
  	int target2 = sh->ops.target2;
  	struct r5dev *tgt = &sh->dev[target];
  	struct r5dev *tgt2 = &sh->dev[target2];
  	struct dma_async_tx_descriptor *tx;
  	struct page **blocks = to_addr_page(percpu, 0);
  	unsigned int *offs = to_addr_offs(sh, percpu);
  	struct async_submit_ctl submit;
  
  	BUG_ON(sh->batch_head);
  	pr_debug("%s: stripe %llu block1: %d block2: %d\n",
  		 __func__, (unsigned long long)sh->sector, target, target2);
  	BUG_ON(target < 0 || target2 < 0);
  	BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
  	BUG_ON(!test_bit(R5_Wantcompute, &tgt2->flags));
  
  	/* we need to open-code set_syndrome_sources to handle the
  	 * slot number conversion for 'faila' and 'failb'
  	 */
  	for (i = 0; i < disks ; i++) {
  		offs[i] = 0;
  		blocks[i] = NULL;
  	}
  	count = 0;
  	i = d0_idx;
  	do {
  		int slot = raid6_idx_to_slot(i, sh, &count, syndrome_disks);
  
  		offs[slot] = sh->dev[i].offset;
  		blocks[slot] = sh->dev[i].page;
  
  		if (i == target)
  			faila = slot;
  		if (i == target2)
  			failb = slot;
  		i = raid6_next_disk(i, disks);
  	} while (i != d0_idx);
  
  	BUG_ON(faila == failb);
  	if (failb < faila)
  		swap(faila, failb);
  	pr_debug("%s: stripe: %llu faila: %d failb: %d\n",
  		 __func__, (unsigned long long)sh->sector, faila, failb);
  
  	atomic_inc(&sh->count);
  
  	if (failb == syndrome_disks+1) {
  		/* Q disk is one of the missing disks */
  		if (faila == syndrome_disks) {
  			/* Missing P+Q, just recompute */
  			init_async_submit(&submit, ASYNC_TX_FENCE, NULL,
  					  ops_complete_compute, sh,
  					  to_addr_conv(sh, percpu, 0));
  			return async_gen_syndrome(blocks, offs, syndrome_disks+2,
  						  RAID5_STRIPE_SIZE(sh->raid_conf),
  						  &submit);
  		} else {
  			struct page *dest;
  			unsigned int dest_off;
  			int data_target;
  			int qd_idx = sh->qd_idx;
  
  			/* Missing D+Q: recompute D from P, then recompute Q */
  			if (target == qd_idx)
  				data_target = target2;
  			else
  				data_target = target;
  
  			count = 0;
  			for (i = disks; i-- ; ) {
  				if (i == data_target || i == qd_idx)
  					continue;
  				offs[count] = sh->dev[i].offset;
  				blocks[count++] = sh->dev[i].page;
  			}
  			dest = sh->dev[data_target].page;
  			dest_off = sh->dev[data_target].offset;
  			init_async_submit(&submit,
  					  ASYNC_TX_FENCE|ASYNC_TX_XOR_ZERO_DST,
  					  NULL, NULL, NULL,
  					  to_addr_conv(sh, percpu, 0));
  			tx = async_xor_offs(dest, dest_off, blocks, offs, count,
  				       RAID5_STRIPE_SIZE(sh->raid_conf),
  				       &submit);
  
  			count = set_syndrome_sources(blocks, offs, sh, SYNDROME_SRC_ALL);
  			init_async_submit(&submit, ASYNC_TX_FENCE, tx,
  					  ops_complete_compute, sh,
  					  to_addr_conv(sh, percpu, 0));
  			return async_gen_syndrome(blocks, offs, count+2,
  						  RAID5_STRIPE_SIZE(sh->raid_conf),
  						  &submit);
  		}
  	} else {
  		init_async_submit(&submit, ASYNC_TX_FENCE, NULL,
  				  ops_complete_compute, sh,
  				  to_addr_conv(sh, percpu, 0));
  		if (failb == syndrome_disks) {
  			/* We're missing D+P. */
  			return async_raid6_datap_recov(syndrome_disks+2,
  						RAID5_STRIPE_SIZE(sh->raid_conf),
  						faila,
  						blocks, offs, &submit);
  		} else {
  			/* We're missing D+D. */
  			return async_raid6_2data_recov(syndrome_disks+2,
  						RAID5_STRIPE_SIZE(sh->raid_conf),
  						faila, failb,
  						blocks, offs, &submit);
  		}
  	}
  }
  
  static void ops_complete_prexor(void *stripe_head_ref)
  {
  	struct stripe_head *sh = stripe_head_ref;
  
  	pr_debug("%s: stripe %llu\n", __func__,
  		(unsigned long long)sh->sector);
  
  	if (r5c_is_writeback(sh->raid_conf->log))
  		/*
  		 * raid5-cache write back uses orig_page during prexor.
  		 * After prexor, it is time to free orig_page
  		 */
  		r5c_release_extra_page(sh);
  }
  
  static struct dma_async_tx_descriptor *
  ops_run_prexor5(struct stripe_head *sh, struct raid5_percpu *percpu,
  		struct dma_async_tx_descriptor *tx)
  {
  	int disks = sh->disks;
  	struct page **xor_srcs = to_addr_page(percpu, 0);
  	unsigned int *off_srcs = to_addr_offs(sh, percpu);
  	int count = 0, pd_idx = sh->pd_idx, i;
  	struct async_submit_ctl submit;
  
  	/* existing parity data subtracted */
  	unsigned int off_dest = off_srcs[count] = sh->dev[pd_idx].offset;
  	struct page *xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
  
  	BUG_ON(sh->batch_head);
  	pr_debug("%s: stripe %llu\n", __func__,
  		(unsigned long long)sh->sector);
  
  	for (i = disks; i--; ) {
  		struct r5dev *dev = &sh->dev[i];
  		/* Only process blocks that are known to be uptodate */
  		if (test_bit(R5_InJournal, &dev->flags)) {
  			/*
  			 * For this case, PAGE_SIZE must be equal to 4KB and
  			 * page offset is zero.
  			 */
  			off_srcs[count] = dev->offset;
  			xor_srcs[count++] = dev->orig_page;
  		} else if (test_bit(R5_Wantdrain, &dev->flags)) {
  			off_srcs[count] = dev->offset;
  			xor_srcs[count++] = dev->page;
  		}
  	}
  
  	init_async_submit(&submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
  			  ops_complete_prexor, sh, to_addr_conv(sh, percpu, 0));
  	tx = async_xor_offs(xor_dest, off_dest, xor_srcs, off_srcs, count,
  			RAID5_STRIPE_SIZE(sh->raid_conf), &submit);
  
  	return tx;
  }
  
  static struct dma_async_tx_descriptor *
  ops_run_prexor6(struct stripe_head *sh, struct raid5_percpu *percpu,
  		struct dma_async_tx_descriptor *tx)
  {
  	struct page **blocks = to_addr_page(percpu, 0);
  	unsigned int *offs = to_addr_offs(sh, percpu);
  	int count;
  	struct async_submit_ctl submit;
  
  	pr_debug("%s: stripe %llu\n", __func__,
  		(unsigned long long)sh->sector);
  
  	count = set_syndrome_sources(blocks, offs, sh, SYNDROME_SRC_WANT_DRAIN);
  
  	init_async_submit(&submit, ASYNC_TX_FENCE|ASYNC_TX_PQ_XOR_DST, tx,
  			  ops_complete_prexor, sh, to_addr_conv(sh, percpu, 0));
  	tx = async_gen_syndrome(blocks, offs, count+2,
  			RAID5_STRIPE_SIZE(sh->raid_conf), &submit);
  
  	return tx;
  }
  
  static struct dma_async_tx_descriptor *
  ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
  {
  	struct r5conf *conf = sh->raid_conf;
  	int disks = sh->disks;
  	int i;
  	struct stripe_head *head_sh = sh;
  
  	pr_debug("%s: stripe %llu\n", __func__,
  		(unsigned long long)sh->sector);
  
  	for (i = disks; i--; ) {
  		struct r5dev *dev;
  		struct bio *chosen;
  
  		sh = head_sh;
  		if (test_and_clear_bit(R5_Wantdrain, &head_sh->dev[i].flags)) {
  			struct bio *wbi;
  
  again:
  			dev = &sh->dev[i];
  			/*
  			 * clear R5_InJournal, so when rewriting a page in
  			 * journal, it is not skipped by r5l_log_stripe()
  			 */
  			clear_bit(R5_InJournal, &dev->flags);
  			spin_lock_irq(&sh->stripe_lock);
  			chosen = dev->towrite;
  			dev->towrite = NULL;
  			sh->overwrite_disks = 0;
  			BUG_ON(dev->written);
  			wbi = dev->written = chosen;
  			spin_unlock_irq(&sh->stripe_lock);
  			WARN_ON(dev->page != dev->orig_page);
  
  			while (wbi && wbi->bi_iter.bi_sector <
  				dev->sector + RAID5_STRIPE_SECTORS(conf)) {
  				if (wbi->bi_opf & REQ_FUA)
  					set_bit(R5_WantFUA, &dev->flags);
  				if (wbi->bi_opf & REQ_SYNC)
  					set_bit(R5_SyncIO, &dev->flags);
  				if (bio_op(wbi) == REQ_OP_DISCARD)
  					set_bit(R5_Discard, &dev->flags);
  				else {
  					tx = async_copy_data(1, wbi, &dev->page,
  							     dev->offset,
  							     dev->sector, tx, sh,
  							     r5c_is_writeback(conf->log));
  					if (dev->page != dev->orig_page &&
  					    !r5c_is_writeback(conf->log)) {
  						set_bit(R5_SkipCopy, &dev->flags);
  						clear_bit(R5_UPTODATE, &dev->flags);
  						clear_bit(R5_OVERWRITE, &dev->flags);
  					}
  				}
  				wbi = r5_next_bio(conf, wbi, dev->sector);
  			}
  
  			if (head_sh->batch_head) {
  				sh = list_first_entry(&sh->batch_list,
  						      struct stripe_head,
  						      batch_list);
  				if (sh == head_sh)
  					continue;
  				goto again;
  			}
  		}
  	}
  
  	return tx;
  }
  
  static void ops_complete_reconstruct(void *stripe_head_ref)
  {
  	struct stripe_head *sh = stripe_head_ref;
  	int disks = sh->disks;
  	int pd_idx = sh->pd_idx;
  	int qd_idx = sh->qd_idx;
  	int i;
  	bool fua = false, sync = false, discard = false;
  
  	pr_debug("%s: stripe %llu\n", __func__,
  		(unsigned long long)sh->sector);
  
  	for (i = disks; i--; ) {
  		fua |= test_bit(R5_WantFUA, &sh->dev[i].flags);
  		sync |= test_bit(R5_SyncIO, &sh->dev[i].flags);
  		discard |= test_bit(R5_Discard, &sh->dev[i].flags);
  	}
  
  	for (i = disks; i--; ) {
  		struct r5dev *dev = &sh->dev[i];
  
  		if (dev->written || i == pd_idx || i == qd_idx) {
  			if (!discard && !test_bit(R5_SkipCopy, &dev->flags)) {
  				set_bit(R5_UPTODATE, &dev->flags);
  				if (test_bit(STRIPE_EXPAND_READY, &sh->state))
  					set_bit(R5_Expanded, &dev->flags);
  			}
  			if (fua)
  				set_bit(R5_WantFUA, &dev->flags);
  			if (sync)
  				set_bit(R5_SyncIO, &dev->flags);
  		}
  	}
  
  	if (sh->reconstruct_state == reconstruct_state_drain_run)
  		sh->reconstruct_state = reconstruct_state_drain_result;
  	else if (sh->reconstruct_state == reconstruct_state_prexor_drain_run)
  		sh->reconstruct_state = reconstruct_state_prexor_drain_result;
  	else {
  		BUG_ON(sh->reconstruct_state != reconstruct_state_run);
  		sh->reconstruct_state = reconstruct_state_result;
  	}
  
  	set_bit(STRIPE_HANDLE, &sh->state);
  	raid5_release_stripe(sh);
  }
  
  static void
  ops_run_reconstruct5(struct stripe_head *sh, struct raid5_percpu *percpu,
  		     struct dma_async_tx_descriptor *tx)
  {
  	int disks = sh->disks;
  	struct page **xor_srcs;
  	unsigned int *off_srcs;
  	struct async_submit_ctl submit;
  	int count, pd_idx = sh->pd_idx, i;
  	struct page *xor_dest;
  	unsigned int off_dest;
  	int prexor = 0;
  	unsigned long flags;
  	int j = 0;
  	struct stripe_head *head_sh = sh;
  	int last_stripe;
  
  	pr_debug("%s: stripe %llu\n", __func__,
  		(unsigned long long)sh->sector);
  
  	for (i = 0; i < sh->disks; i++) {
  		if (pd_idx == i)
  			continue;
  		if (!test_bit(R5_Discard, &sh->dev[i].flags))
  			break;
  	}
  	if (i >= sh->disks) {
  		atomic_inc(&sh->count);
  		set_bit(R5_Discard, &sh->dev[pd_idx].flags);
  		ops_complete_reconstruct(sh);
  		return;
  	}
  again:
  	count = 0;
  	xor_srcs = to_addr_page(percpu, j);
  	off_srcs = to_addr_offs(sh, percpu);
  	/* check if prexor is active which means only process blocks
  	 * that are part of a read-modify-write (written)
  	 */
  	if (head_sh->reconstruct_state == reconstruct_state_prexor_drain_run) {
  		prexor = 1;
  		off_dest = off_srcs[count] = sh->dev[pd_idx].offset;
  		xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
  		for (i = disks; i--; ) {
  			struct r5dev *dev = &sh->dev[i];
  			if (head_sh->dev[i].written ||
  			    test_bit(R5_InJournal, &head_sh->dev[i].flags)) {
  				off_srcs[count] = dev->offset;
  				xor_srcs[count++] = dev->page;
  			}
  		}
  	} else {
  		xor_dest = sh->dev[pd_idx].page;
  		off_dest = sh->dev[pd_idx].offset;
  		for (i = disks; i--; ) {
  			struct r5dev *dev = &sh->dev[i];
  			if (i != pd_idx) {
  				off_srcs[count] = dev->offset;
  				xor_srcs[count++] = dev->page;
  			}
  		}
  	}
  
  	/* 1/ if we prexor'd then the dest is reused as a source
  	 * 2/ if we did not prexor then we are redoing the parity
  	 * set ASYNC_TX_XOR_DROP_DST and ASYNC_TX_XOR_ZERO_DST
  	 * for the synchronous xor case
  	 */
  	last_stripe = !head_sh->batch_head ||
  		list_first_entry(&sh->batch_list,
  				 struct stripe_head, batch_list) == head_sh;
  	if (last_stripe) {
  		flags = ASYNC_TX_ACK |
  			(prexor ? ASYNC_TX_XOR_DROP_DST : ASYNC_TX_XOR_ZERO_DST);
  
  		atomic_inc(&head_sh->count);
  		init_async_submit(&submit, flags, tx, ops_complete_reconstruct, head_sh,
  				  to_addr_conv(sh, percpu, j));
  	} else {
  		flags = prexor ? ASYNC_TX_XOR_DROP_DST : ASYNC_TX_XOR_ZERO_DST;
  		init_async_submit(&submit, flags, tx, NULL, NULL,
  				  to_addr_conv(sh, percpu, j));
  	}
  
  	if (unlikely(count == 1))
  		tx = async_memcpy(xor_dest, xor_srcs[0], off_dest, off_srcs[0],
  				RAID5_STRIPE_SIZE(sh->raid_conf), &submit);
  	else
  		tx = async_xor_offs(xor_dest, off_dest, xor_srcs, off_srcs, count,
  				RAID5_STRIPE_SIZE(sh->raid_conf), &submit);
  	if (!last_stripe) {
  		j++;
  		sh = list_first_entry(&sh->batch_list, struct stripe_head,
  				      batch_list);
  		goto again;
  	}
  }
  
  static void
  ops_run_reconstruct6(struct stripe_head *sh, struct raid5_percpu *percpu,
  		     struct dma_async_tx_descriptor *tx)
  {
  	struct async_submit_ctl submit;
  	struct page **blocks;
  	unsigned int *offs;
  	int count, i, j = 0;
  	struct stripe_head *head_sh = sh;
  	int last_stripe;
  	int synflags;
  	unsigned long txflags;
  
  	pr_debug("%s: stripe %llu\n", __func__, (unsigned long long)sh->sector);
  
  	for (i = 0; i < sh->disks; i++) {
  		if (sh->pd_idx == i || sh->qd_idx == i)
  			continue;
  		if (!test_bit(R5_Discard, &sh->dev[i].flags))
  			break;
  	}
  	if (i >= sh->disks) {
  		atomic_inc(&sh->count);
  		set_bit(R5_Discard, &sh->dev[sh->pd_idx].flags);
  		set_bit(R5_Discard, &sh->dev[sh->qd_idx].flags);
  		ops_complete_reconstruct(sh);
  		return;
  	}
  
  again:
  	blocks = to_addr_page(percpu, j);
  	offs = to_addr_offs(sh, percpu);
  
  	if (sh->reconstruct_state == reconstruct_state_prexor_drain_run) {
  		synflags = SYNDROME_SRC_WRITTEN;
  		txflags = ASYNC_TX_ACK | ASYNC_TX_PQ_XOR_DST;
  	} else {
  		synflags = SYNDROME_SRC_ALL;
  		txflags = ASYNC_TX_ACK;
  	}
  
  	count = set_syndrome_sources(blocks, offs, sh, synflags);
  	last_stripe = !head_sh->batch_head ||
  		list_first_entry(&sh->batch_list,
  				 struct stripe_head, batch_list) == head_sh;
  
  	if (last_stripe) {
  		atomic_inc(&head_sh->count);
  		init_async_submit(&submit, txflags, tx, ops_complete_reconstruct,
  				  head_sh, to_addr_conv(sh, percpu, j));
  	} else
  		init_async_submit(&submit, 0, tx, NULL, NULL,
  				  to_addr_conv(sh, percpu, j));
  	tx = async_gen_syndrome(blocks, offs, count+2,
  			RAID5_STRIPE_SIZE(sh->raid_conf),  &submit);
  	if (!last_stripe) {
  		j++;
  		sh = list_first_entry(&sh->batch_list, struct stripe_head,
  				      batch_list);
  		goto again;
  	}
  }
  
  static void ops_complete_check(void *stripe_head_ref)
  {
  	struct stripe_head *sh = stripe_head_ref;
  
  	pr_debug("%s: stripe %llu\n", __func__,
  		(unsigned long long)sh->sector);
  
  	sh->check_state = check_state_check_result;
  	set_bit(STRIPE_HANDLE, &sh->state);
  	raid5_release_stripe(sh);
  }
  
  static void ops_run_check_p(struct stripe_head *sh, struct raid5_percpu *percpu)
  {
  	int disks = sh->disks;
  	int pd_idx = sh->pd_idx;
  	int qd_idx = sh->qd_idx;
  	struct page *xor_dest;
  	unsigned int off_dest;
  	struct page **xor_srcs = to_addr_page(percpu, 0);
  	unsigned int *off_srcs = to_addr_offs(sh, percpu);
  	struct dma_async_tx_descriptor *tx;
  	struct async_submit_ctl submit;
  	int count;
  	int i;
  
  	pr_debug("%s: stripe %llu\n", __func__,
  		(unsigned long long)sh->sector);
  
  	BUG_ON(sh->batch_head);
  	count = 0;
  	xor_dest = sh->dev[pd_idx].page;
  	off_dest = sh->dev[pd_idx].offset;
  	off_srcs[count] = off_dest;
  	xor_srcs[count++] = xor_dest;
  	for (i = disks; i--; ) {
  		if (i == pd_idx || i == qd_idx)
  			continue;
  		off_srcs[count] = sh->dev[i].offset;
  		xor_srcs[count++] = sh->dev[i].page;
  	}
  
  	init_async_submit(&submit, 0, NULL, NULL, NULL,
  			  to_addr_conv(sh, percpu, 0));
  	tx = async_xor_val_offs(xor_dest, off_dest, xor_srcs, off_srcs, count,
  			   RAID5_STRIPE_SIZE(sh->raid_conf),
  			   &sh->ops.zero_sum_result, &submit);
  
  	atomic_inc(&sh->count);
  	init_async_submit(&submit, ASYNC_TX_ACK, tx, ops_complete_check, sh, NULL);
  	tx = async_trigger_callback(&submit);
  }
  
  static void ops_run_check_pq(struct stripe_head *sh, struct raid5_percpu *percpu, int checkp)
  {
  	struct page **srcs = to_addr_page(percpu, 0);
  	unsigned int *offs = to_addr_offs(sh, percpu);
  	struct async_submit_ctl submit;
  	int count;
  
  	pr_debug("%s: stripe %llu checkp: %d\n", __func__,
  		(unsigned long long)sh->sector, checkp);
  
  	BUG_ON(sh->batch_head);
  	count = set_syndrome_sources(srcs, offs, sh, SYNDROME_SRC_ALL);
  	if (!checkp)
  		srcs[count] = NULL;
  
  	atomic_inc(&sh->count);
  	init_async_submit(&submit, ASYNC_TX_ACK, NULL, ops_complete_check,
  			  sh, to_addr_conv(sh, percpu, 0));
  	async_syndrome_val(srcs, offs, count+2,
  			   RAID5_STRIPE_SIZE(sh->raid_conf),
  			   &sh->ops.zero_sum_result, percpu->spare_page, 0, &submit);
  }
  
  static void raid_run_ops(struct stripe_head *sh, unsigned long ops_request)
  {
  	int overlap_clear = 0, i, disks = sh->disks;
  	struct dma_async_tx_descriptor *tx = NULL;
  	struct r5conf *conf = sh->raid_conf;
  	int level = conf->level;
  	struct raid5_percpu *percpu;
  	unsigned long cpu;
  
  	cpu = get_cpu_light();
  	percpu = per_cpu_ptr(conf->percpu, cpu);
  	spin_lock(&percpu->lock);
  	if (test_bit(STRIPE_OP_BIOFILL, &ops_request)) {
  		ops_run_biofill(sh);
  		overlap_clear++;
  	}
  
  	if (test_bit(STRIPE_OP_COMPUTE_BLK, &ops_request)) {
  		if (level < 6)
  			tx = ops_run_compute5(sh, percpu);
  		else {
  			if (sh->ops.target2 < 0 || sh->ops.target < 0)
  				tx = ops_run_compute6_1(sh, percpu);
  			else
  				tx = ops_run_compute6_2(sh, percpu);
  		}
  		/* terminate the chain if reconstruct is not set to be run */
  		if (tx && !test_bit(STRIPE_OP_RECONSTRUCT, &ops_request))
  			async_tx_ack(tx);
  	}
  
  	if (test_bit(STRIPE_OP_PREXOR, &ops_request)) {
  		if (level < 6)
  			tx = ops_run_prexor5(sh, percpu, tx);
  		else
  			tx = ops_run_prexor6(sh, percpu, tx);
  	}
  
  	if (test_bit(STRIPE_OP_PARTIAL_PARITY, &ops_request))
  		tx = ops_run_partial_parity(sh, percpu, tx);
  
  	if (test_bit(STRIPE_OP_BIODRAIN, &ops_request)) {
  		tx = ops_run_biodrain(sh, tx);
  		overlap_clear++;
  	}
  
  	if (test_bit(STRIPE_OP_RECONSTRUCT, &ops_request)) {
  		if (level < 6)
  			ops_run_reconstruct5(sh, percpu, tx);
  		else
  			ops_run_reconstruct6(sh, percpu, tx);
  	}
  
  	if (test_bit(STRIPE_OP_CHECK, &ops_request)) {
  		if (sh->check_state == check_state_run)
  			ops_run_check_p(sh, percpu);
  		else if (sh->check_state == check_state_run_q)
  			ops_run_check_pq(sh, percpu, 0);
  		else if (sh->check_state == check_state_run_pq)
  			ops_run_check_pq(sh, percpu, 1);
  		else
  			BUG();
  	}
  
  	if (overlap_clear && !sh->batch_head)
  		for (i = disks; i--; ) {
  			struct r5dev *dev = &sh->dev[i];
  			if (test_and_clear_bit(R5_Overlap, &dev->flags))
  				wake_up(&sh->raid_conf->wait_for_overlap);
  		}
  	spin_unlock(&percpu->lock);
  	put_cpu_light();
  }
  
  static void free_stripe(struct kmem_cache *sc, struct stripe_head *sh)
  {
  #if PAGE_SIZE != DEFAULT_STRIPE_SIZE
  	kfree(sh->pages);
  #endif
  	if (sh->ppl_page)
  		__free_page(sh->ppl_page);
  	kmem_cache_free(sc, sh);
  }
  
  static struct stripe_head *alloc_stripe(struct kmem_cache *sc, gfp_t gfp,
  	int disks, struct r5conf *conf)
  {
  	struct stripe_head *sh;
  	int i;
  
  	sh = kmem_cache_zalloc(sc, gfp);
  	if (sh) {
  		spin_lock_init(&sh->stripe_lock);
  		spin_lock_init(&sh->batch_lock);
  		INIT_LIST_HEAD(&sh->batch_list);
  		INIT_LIST_HEAD(&sh->lru);
  		INIT_LIST_HEAD(&sh->r5c);
  		INIT_LIST_HEAD(&sh->log_list);
  		atomic_set(&sh->count, 1);
  		sh->raid_conf = conf;
  		sh->log_start = MaxSector;
  		for (i = 0; i < disks; i++) {
  			struct r5dev *dev = &sh->dev[i];
  
  			bio_init(&dev->req, &dev->vec, 1);
  			bio_init(&dev->rreq, &dev->rvec, 1);
  		}
  
  		if (raid5_has_ppl(conf)) {
  			sh->ppl_page = alloc_page(gfp);
  			if (!sh->ppl_page) {
  				free_stripe(sc, sh);
  				return NULL;
  			}
  		}
  #if PAGE_SIZE != DEFAULT_STRIPE_SIZE
  		if (init_stripe_shared_pages(sh, conf, disks)) {
  			free_stripe(sc, sh);
  			return NULL;
  		}
  #endif
  	}
  	return sh;
  }
  static int grow_one_stripe(struct r5conf *conf, gfp_t gfp)
  {
  	struct stripe_head *sh;
  
  	sh = alloc_stripe(conf->slab_cache, gfp, conf->pool_size, conf);
  	if (!sh)
  		return 0;
  
  	if (grow_buffers(sh, gfp)) {
  		shrink_buffers(sh);
  		free_stripe(conf->slab_cache, sh);
  		return 0;
  	}
  	sh->hash_lock_index =
  		conf->max_nr_stripes % NR_STRIPE_HASH_LOCKS;
  	/* we just created an active stripe so... */
  	atomic_inc(&conf->active_stripes);
  
  	raid5_release_stripe(sh);
  	conf->max_nr_stripes++;
  	return 1;
  }
  
  static int grow_stripes(struct r5conf *conf, int num)
  {
  	struct kmem_cache *sc;
  	size_t namelen = sizeof(conf->cache_name[0]);
  	int devs = max(conf->raid_disks, conf->previous_raid_disks);
  
  	if (conf->mddev->gendisk)
  		snprintf(conf->cache_name[0], namelen,
  			"raid%d-%s", conf->level, mdname(conf->mddev));
  	else
  		snprintf(conf->cache_name[0], namelen,
  			"raid%d-%p", conf->level, conf->mddev);
  	snprintf(conf->cache_name[1], namelen, "%.27s-alt", conf->cache_name[0]);
  
  	conf->active_name = 0;
  	sc = kmem_cache_create(conf->cache_name[conf->active_name],
  			       sizeof(struct stripe_head)+(devs-1)*sizeof(struct r5dev),
  			       0, 0, NULL);
  	if (!sc)
  		return 1;
  	conf->slab_cache = sc;
  	conf->pool_size = devs;
  	while (num--)
  		if (!grow_one_stripe(conf, GFP_KERNEL))
  			return 1;
  
  	return 0;
  }
  
  /**
   * scribble_alloc - allocate percpu scribble buffer for required size
   *		    of the scribble region
   * @percpu: from for_each_present_cpu() of the caller
   * @num: total number of disks in the array
   * @cnt: scribble objs count for required size of the scribble region
   *
   * The scribble buffer size must be enough to contain:
   * 1/ a struct page pointer for each device in the array +2
   * 2/ room to convert each entry in (1) to its corresponding dma
   *    (dma_map_page()) or page (page_address()) address.
   *
   * Note: the +2 is for the destination buffers of the ddf/raid6 case where we
   * calculate over all devices (not just the data blocks), using zeros in place
   * of the P and Q blocks.
   */
  static int scribble_alloc(struct raid5_percpu *percpu,
  			  int num, int cnt)
  {
  	size_t obj_size =
  		sizeof(struct page *) * (num + 2) +
  		sizeof(addr_conv_t) * (num + 2) +
  		sizeof(unsigned int) * (num + 2);
  	void *scribble;
  
  	/*
  	 * If here is in raid array suspend context, it is in memalloc noio
  	 * context as well, there is no potential recursive memory reclaim
  	 * I/Os with the GFP_KERNEL flag.
  	 */
  	scribble = kvmalloc_array(cnt, obj_size, GFP_KERNEL);
  	if (!scribble)
  		return -ENOMEM;
  
  	kvfree(percpu->scribble);
  
  	percpu->scribble = scribble;
  	percpu->scribble_obj_size = obj_size;
  	return 0;
  }
  
  static int resize_chunks(struct r5conf *conf, int new_disks, int new_sectors)
  {
  	unsigned long cpu;
  	int err = 0;
  
  	/*
  	 * Never shrink. And mddev_suspend() could deadlock if this is called
  	 * from raid5d. In that case, scribble_disks and scribble_sectors
  	 * should equal to new_disks and new_sectors
  	 */
  	if (conf->scribble_disks >= new_disks &&
  	    conf->scribble_sectors >= new_sectors)
  		return 0;
  	mddev_suspend(conf->mddev);
  	get_online_cpus();
  
  	for_each_present_cpu(cpu) {
  		struct raid5_percpu *percpu;
  
  		percpu = per_cpu_ptr(conf->percpu, cpu);
  		err = scribble_alloc(percpu, new_disks,
  				     new_sectors / RAID5_STRIPE_SECTORS(conf));
  		if (err)
  			break;
  	}
  
  	put_online_cpus();
  	mddev_resume(conf->mddev);
  	if (!err) {
  		conf->scribble_disks = new_disks;
  		conf->scribble_sectors = new_sectors;
  	}
  	return err;
  }
  
  static int resize_stripes(struct r5conf *conf, int newsize)
  {
  	/* Make all the stripes able to hold 'newsize' devices.
  	 * New slots in each stripe get 'page' set to a new page.
  	 *
  	 * This happens in stages:
  	 * 1/ create a new kmem_cache and allocate the required number of
  	 *    stripe_heads.
  	 * 2/ gather all the old stripe_heads and transfer the pages across
  	 *    to the new stripe_heads.  This will have the side effect of
  	 *    freezing the array as once all stripe_heads have been collected,
  	 *    no IO will be possible.  Old stripe heads are freed once their
  	 *    pages have been transferred over, and the old kmem_cache is
  	 *    freed when all stripes are done.
  	 * 3/ reallocate conf->disks to be suitable bigger.  If this fails,
  	 *    we simple return a failure status - no need to clean anything up.
  	 * 4/ allocate new pages for the new slots in the new stripe_heads.
  	 *    If this fails, we don't bother trying the shrink the
  	 *    stripe_heads down again, we just leave them as they are.
  	 *    As each stripe_head is processed the new one is released into
  	 *    active service.
  	 *
  	 * Once step2 is started, we cannot afford to wait for a write,
  	 * so we use GFP_NOIO allocations.
  	 */
  	struct stripe_head *osh, *nsh;
  	LIST_HEAD(newstripes);
  	struct disk_info *ndisks;
  	int err = 0;
  	struct kmem_cache *sc;
  	int i;
  	int hash, cnt;
  
  	md_allow_write(conf->mddev);
  
  	/* Step 1 */
  	sc = kmem_cache_create(conf->cache_name[1-conf->active_name],
  			       sizeof(struct stripe_head)+(newsize-1)*sizeof(struct r5dev),
  			       0, 0, NULL);
  	if (!sc)
  		return -ENOMEM;
  
  	/* Need to ensure auto-resizing doesn't interfere */
  	mutex_lock(&conf->cache_size_mutex);
  
  	for (i = conf->max_nr_stripes; i; i--) {
  		nsh = alloc_stripe(sc, GFP_KERNEL, newsize, conf);
  		if (!nsh)
  			break;
  
  		list_add(&nsh->lru, &newstripes);
  	}
  	if (i) {
  		/* didn't get enough, give up */
  		while (!list_empty(&newstripes)) {
  			nsh = list_entry(newstripes.next, struct stripe_head, lru);
  			list_del(&nsh->lru);
  			free_stripe(sc, nsh);
  		}
  		kmem_cache_destroy(sc);
  		mutex_unlock(&conf->cache_size_mutex);
  		return -ENOMEM;
  	}
  	/* Step 2 - Must use GFP_NOIO now.
  	 * OK, we have enough stripes, start collecting inactive
  	 * stripes and copying them over
  	 */
  	hash = 0;
  	cnt = 0;
  	list_for_each_entry(nsh, &newstripes, lru) {
  		lock_device_hash_lock(conf, hash);
  		wait_event_cmd(conf->wait_for_stripe,
  				    !list_empty(conf->inactive_list + hash),
  				    unlock_device_hash_lock(conf, hash),
  				    lock_device_hash_lock(conf, hash));
  		osh = get_free_stripe(conf, hash);
  		unlock_device_hash_lock(conf, hash);
  
  #if PAGE_SIZE != DEFAULT_STRIPE_SIZE
  	for (i = 0; i < osh->nr_pages; i++) {
  		nsh->pages[i] = osh->pages[i];
  		osh->pages[i] = NULL;
  	}
  #endif
  		for(i=0; i<conf->pool_size; i++) {
  			nsh->dev[i].page = osh->dev[i].page;
  			nsh->dev[i].orig_page = osh->dev[i].page;
  			nsh->dev[i].offset = osh->dev[i].offset;
  		}
  		nsh->hash_lock_index = hash;
  		free_stripe(conf->slab_cache, osh);
  		cnt++;
  		if (cnt >= conf->max_nr_stripes / NR_STRIPE_HASH_LOCKS +
  		    !!((conf->max_nr_stripes % NR_STRIPE_HASH_LOCKS) > hash)) {
  			hash++;
  			cnt = 0;
  		}
  	}
  	kmem_cache_destroy(conf->slab_cache);
  
  	/* Step 3.
  	 * At this point, we are holding all the stripes so the array
  	 * is completely stalled, so now is a good time to resize
  	 * conf->disks and the scribble region
  	 */
  	ndisks = kcalloc(newsize, sizeof(struct disk_info), GFP_NOIO);
  	if (ndisks) {
  		for (i = 0; i < conf->pool_size; i++)
  			ndisks[i] = conf->disks[i];
  
  		for (i = conf->pool_size; i < newsize; i++) {
  			ndisks[i].extra_page = alloc_page(GFP_NOIO);
  			if (!ndisks[i].extra_page)
  				err = -ENOMEM;
  		}
  
  		if (err) {
  			for (i = conf->pool_size; i < newsize; i++)
  				if (ndisks[i].extra_page)
  					put_page(ndisks[i].extra_page);
  			kfree(ndisks);
  		} else {
  			kfree(conf->disks);
  			conf->disks = ndisks;
  		}
  	} else
  		err = -ENOMEM;
  
  	conf->slab_cache = sc;
  	conf->active_name = 1-conf->active_name;
  
  	/* Step 4, return new stripes to service */
  	while(!list_empty(&newstripes)) {
  		nsh = list_entry(newstripes.next, struct stripe_head, lru);
  		list_del_init(&nsh->lru);
  
  #if PAGE_SIZE != DEFAULT_STRIPE_SIZE
  		for (i = 0; i < nsh->nr_pages; i++) {
  			if (nsh->pages[i])
  				continue;
  			nsh->pages[i] = alloc_page(GFP_NOIO);
  			if (!nsh->pages[i])
  				err = -ENOMEM;
  		}
  
  		for (i = conf->raid_disks; i < newsize; i++) {
  			if (nsh->dev[i].page)
  				continue;
  			nsh->dev[i].page = raid5_get_dev_page(nsh, i);
  			nsh->dev[i].orig_page = nsh->dev[i].page;
  			nsh->dev[i].offset = raid5_get_page_offset(nsh, i);
  		}
  #else
  		for (i=conf->raid_disks; i < newsize; i++)
  			if (nsh->dev[i].page == NULL) {
  				struct page *p = alloc_page(GFP_NOIO);
  				nsh->dev[i].page = p;
  				nsh->dev[i].orig_page = p;
  				nsh->dev[i].offset = 0;
  				if (!p)
  					err = -ENOMEM;
  			}
  #endif
  		raid5_release_stripe(nsh);
  	}
  	/* critical section pass, GFP_NOIO no longer needed */
  
  	if (!err)
  		conf->pool_size = newsize;
  	mutex_unlock(&conf->cache_size_mutex);
  
  	return err;
  }
  
  static int drop_one_stripe(struct r5conf *conf)
  {
  	struct stripe_head *sh;
  	int hash = (conf->max_nr_stripes - 1) & STRIPE_HASH_LOCKS_MASK;
  
  	spin_lock_irq(conf->hash_locks + hash);
  	sh = get_free_stripe(conf, hash);
  	spin_unlock_irq(conf->hash_locks + hash);
  	if (!sh)
  		return 0;
  	BUG_ON(atomic_read(&sh->count));
  	shrink_buffers(sh);
  	free_stripe(conf->slab_cache, sh);
  	atomic_dec(&conf->active_stripes);
  	conf->max_nr_stripes--;
  	return 1;
  }
  
  static void shrink_stripes(struct r5conf *conf)
  {
  	while (conf->max_nr_stripes &&
  	       drop_one_stripe(conf))
  		;
  
  	kmem_cache_destroy(conf->slab_cache);
  	conf->slab_cache = NULL;
  }
  
  static void raid5_end_read_request(struct bio * bi)
  {
  	struct stripe_head *sh = bi->bi_private;
  	struct r5conf *conf = sh->raid_conf;
  	int disks = sh->disks, i;
  	char b[BDEVNAME_SIZE];
  	struct md_rdev *rdev = NULL;
  	sector_t s;
  
  	for (i=0 ; i<disks; i++)
  		if (bi == &sh->dev[i].req)
  			break;
  
  	pr_debug("end_read_request %llu/%d, count: %d, error %d.\n",
  		(unsigned long long)sh->sector, i, atomic_read(&sh->count),
  		bi->bi_status);
  	if (i == disks) {
  		bio_reset(bi);
  		BUG();
  		return;
  	}
  	if (test_bit(R5_ReadRepl, &sh->dev[i].flags))
  		/* If replacement finished while this request was outstanding,
  		 * 'replacement' might be NULL already.
  		 * In that case it moved down to 'rdev'.
  		 * rdev is not removed until all requests are finished.
  		 */
  		rdev = conf->disks[i].replacement;
  	if (!rdev)
  		rdev = conf->disks[i].rdev;
  
  	if (use_new_offset(conf, sh))
  		s = sh->sector + rdev->new_data_offset;
  	else
  		s = sh->sector + rdev->data_offset;
  	if (!bi->bi_status) {
  		set_bit(R5_UPTODATE, &sh->dev[i].flags);
  		if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
  			/* Note that this cannot happen on a
  			 * replacement device.  We just fail those on
  			 * any error
  			 */
  			pr_info_ratelimited(
  				"md/raid:%s: read error corrected (%lu sectors at %llu on %s)\n",
  				mdname(conf->mddev), RAID5_STRIPE_SECTORS(conf),
  				(unsigned long long)s,
  				bdevname(rdev->bdev, b));
  			atomic_add(RAID5_STRIPE_SECTORS(conf), &rdev->corrected_errors);
  			clear_bit(R5_ReadError, &sh->dev[i].flags);
  			clear_bit(R5_ReWrite, &sh->dev[i].flags);
  		} else if (test_bit(R5_ReadNoMerge, &sh->dev[i].flags))
  			clear_bit(R5_ReadNoMerge, &sh->dev[i].flags);
  
  		if (test_bit(R5_InJournal, &sh->dev[i].flags))
  			/*
  			 * end read for a page in journal, this
  			 * must be preparing for prexor in rmw
  			 */
  			set_bit(R5_OrigPageUPTDODATE, &sh->dev[i].flags);
  
  		if (atomic_read(&rdev->read_errors))
  			atomic_set(&rdev->read_errors, 0);
  	} else {
  		const char *bdn = bdevname(rdev->bdev, b);
  		int retry = 0;
  		int set_bad = 0;
  
  		clear_bit(R5_UPTODATE, &sh->dev[i].flags);
  		if (!(bi->bi_status == BLK_STS_PROTECTION))
  			atomic_inc(&rdev->read_errors);
  		if (test_bit(R5_ReadRepl, &sh->dev[i].flags))
  			pr_warn_ratelimited(
  				"md/raid:%s: read error on replacement device (sector %llu on %s).\n",
  				mdname(conf->mddev),
  				(unsigned long long)s,
  				bdn);
  		else if (conf->mddev->degraded >= conf->max_degraded) {
  			set_bad = 1;
  			pr_warn_ratelimited(
  				"md/raid:%s: read error not correctable (sector %llu on %s).\n",
  				mdname(conf->mddev),
  				(unsigned long long)s,
  				bdn);
  		} else if (test_bit(R5_ReWrite, &sh->dev[i].flags)) {
  			/* Oh, no!!! */
  			set_bad = 1;
  			pr_warn_ratelimited(
  				"md/raid:%s: read error NOT corrected!! (sector %llu on %s).\n",
  				mdname(conf->mddev),
  				(unsigned long long)s,
  				bdn);
  		} else if (atomic_read(&rdev->read_errors)
  			 > conf->max_nr_stripes) {
  			if (!test_bit(Faulty, &rdev->flags)) {
  				pr_warn("md/raid:%s: %d read_errors > %d stripes\n",
  				    mdname(conf->mddev),
  				    atomic_read(&rdev->read_errors),
  				    conf->max_nr_stripes);
  				pr_warn("md/raid:%s: Too many read errors, failing device %s.\n",
  				    mdname(conf->mddev), bdn);
  			}
  		} else
  			retry = 1;
  		if (set_bad && test_bit(In_sync, &rdev->flags)
  		    && !test_bit(R5_ReadNoMerge, &sh->dev[i].flags))
  			retry = 1;
  		if (retry)
  			if (sh->qd_idx >= 0 && sh->pd_idx == i)
  				set_bit(R5_ReadError, &sh->dev[i].flags);
  			else if (test_bit(R5_ReadNoMerge, &sh->dev[i].flags)) {
  				set_bit(R5_ReadError, &sh->dev[i].flags);
  				clear_bit(R5_ReadNoMerge, &sh->dev[i].flags);
  			} else
  				set_bit(R5_ReadNoMerge, &sh->dev[i].flags);
  		else {
  			clear_bit(R5_ReadError, &sh->dev[i].flags);
  			clear_bit(R5_ReWrite, &sh->dev[i].flags);
  			if (!(set_bad
  			      && test_bit(In_sync, &rdev->flags)
  			      && rdev_set_badblocks(
  				      rdev, sh->sector, RAID5_STRIPE_SECTORS(conf), 0)))
  				md_error(conf->mddev, rdev);
  		}
  	}
  	rdev_dec_pending(rdev, conf->mddev);
  	bio_reset(bi);
  	clear_bit(R5_LOCKED, &sh->dev[i].flags);
  	set_bit(STRIPE_HANDLE, &sh->state);
  	raid5_release_stripe(sh);
  }
  
  static void raid5_end_write_request(struct bio *bi)
  {
  	struct stripe_head *sh = bi->bi_private;
  	struct r5conf *conf = sh->raid_conf;
  	int disks = sh->disks, i;
  	struct md_rdev *rdev;
  	sector_t first_bad;
  	int bad_sectors;
  	int replacement = 0;
  
  	for (i = 0 ; i < disks; i++) {
  		if (bi == &sh->dev[i].req) {
  			rdev = conf->disks[i].rdev;
  			break;
  		}
  		if (bi == &sh->dev[i].rreq) {
  			rdev = conf->disks[i].replacement;
  			if (rdev)
  				replacement = 1;
  			else
  				/* rdev was removed and 'replacement'
  				 * replaced it.  rdev is not removed
  				 * until all requests are finished.
  				 */
  				rdev = conf->disks[i].rdev;
  			break;
  		}
  	}
  	pr_debug("end_write_request %llu/%d, count %d, error: %d.\n",
  		(unsigned long long)sh->sector, i, atomic_read(&sh->count),
  		bi->bi_status);
  	if (i == disks) {
  		bio_reset(bi);
  		BUG();
  		return;
  	}
  
  	if (replacement) {
  		if (bi->bi_status)
  			md_error(conf->mddev, rdev);
  		else if (is_badblock(rdev, sh->sector,
  				     RAID5_STRIPE_SECTORS(conf),
  				     &first_bad, &bad_sectors))
  			set_bit(R5_MadeGoodRepl, &sh->dev[i].flags);
  	} else {
  		if (bi->bi_status) {
  			set_bit(STRIPE_DEGRADED, &sh->state);
  			set_bit(WriteErrorSeen, &rdev->flags);
  			set_bit(R5_WriteError, &sh->dev[i].flags);
  			if (!test_and_set_bit(WantReplacement, &rdev->flags))
  				set_bit(MD_RECOVERY_NEEDED,
  					&rdev->mddev->recovery);
  		} else if (is_badblock(rdev, sh->sector,
  				       RAID5_STRIPE_SECTORS(conf),
  				       &first_bad, &bad_sectors)) {
  			set_bit(R5_MadeGood, &sh->dev[i].flags);
  			if (test_bit(R5_ReadError, &sh->dev[i].flags))
  				/* That was a successful write so make
  				 * sure it looks like we already did
  				 * a re-write.
  				 */
  				set_bit(R5_ReWrite, &sh->dev[i].flags);
  		}
  	}
  	rdev_dec_pending(rdev, conf->mddev);
  
  	if (sh->batch_head && bi->bi_status && !replacement)
  		set_bit(STRIPE_BATCH_ERR, &sh->batch_head->state);
  
  	bio_reset(bi);
  	if (!test_and_clear_bit(R5_DOUBLE_LOCKED, &sh->dev[i].flags))
  		clear_bit(R5_LOCKED, &sh->dev[i].flags);
  	set_bit(STRIPE_HANDLE, &sh->state);
  	raid5_release_stripe(sh);
  
  	if (sh->batch_head && sh != sh->batch_head)
  		raid5_release_stripe(sh->batch_head);
  }
  
  static void raid5_error(struct mddev *mddev, struct md_rdev *rdev)
  {
  	char b[BDEVNAME_SIZE];
  	struct r5conf *conf = mddev->private;
  	unsigned long flags;
  	pr_debug("raid456: error called\n");
  
  	spin_lock_irqsave(&conf->device_lock, flags);
  
  	if (test_bit(In_sync, &rdev->flags) &&
  	    mddev->degraded == conf->max_degraded) {
  		/*
  		 * Don't allow to achieve failed state
  		 * Don't try to recover this device
  		 */
  		conf->recovery_disabled = mddev->recovery_disabled;
  		spin_unlock_irqrestore(&conf->device_lock, flags);
  		return;
  	}
  
  	set_bit(Faulty, &rdev->flags);
  	clear_bit(In_sync, &rdev->flags);
  	mddev->degraded = raid5_calc_degraded(conf);
  	spin_unlock_irqrestore(&conf->device_lock, flags);
  	set_bit(MD_RECOVERY_INTR, &mddev->recovery);
  
  	set_bit(Blocked, &rdev->flags);
  	set_mask_bits(&mddev->sb_flags, 0,
  		      BIT(MD_SB_CHANGE_DEVS) | BIT(MD_SB_CHANGE_PENDING));
  	pr_crit("md/raid:%s: Disk failure on %s, disabling device.\n"
  		"md/raid:%s: Operation continuing on %d devices.\n",
  		mdname(mddev),
  		bdevname(rdev->bdev, b),
  		mdname(mddev),
  		conf->raid_disks - mddev->degraded);
  	r5c_update_on_rdev_error(mddev, rdev);
  }
  
  /*
   * Input: a 'big' sector number,
   * Output: index of the data and parity disk, and the sector # in them.
   */
  sector_t raid5_compute_sector(struct r5conf *conf, sector_t r_sector,
  			      int previous, int *dd_idx,
  			      struct stripe_head *sh)
  {
  	sector_t stripe, stripe2;
  	sector_t chunk_number;
  	unsigned int chunk_offset;
  	int pd_idx, qd_idx;
  	int ddf_layout = 0;
  	sector_t new_sector;
  	int algorithm = previous ? conf->prev_algo
  				 : conf->algorithm;
  	int sectors_per_chunk = previous ? conf->prev_chunk_sectors
  					 : conf->chunk_sectors;
  	int raid_disks = previous ? conf->previous_raid_disks
  				  : conf->raid_disks;
  	int data_disks = raid_disks - conf->max_degraded;
  
  	/* First compute the information on this sector */
  
  	/*
  	 * Compute the chunk number and the sector offset inside the chunk
  	 */
  	chunk_offset = sector_div(r_sector, sectors_per_chunk);
  	chunk_number = r_sector;
  
  	/*
  	 * Compute the stripe number
  	 */
  	stripe = chunk_number;
  	*dd_idx = sector_div(stripe, data_disks);
  	stripe2 = stripe;
  	/*
  	 * Select the parity disk based on the user selected algorithm.
  	 */
  	pd_idx = qd_idx = -1;
  	switch(conf->level) {
  	case 4:
  		pd_idx = data_disks;
  		break;
  	case 5:
  		switch (algorithm) {
  		case ALGORITHM_LEFT_ASYMMETRIC:
  			pd_idx = data_disks - sector_div(stripe2, raid_disks);
  			if (*dd_idx >= pd_idx)
  				(*dd_idx)++;
  			break;
  		case ALGORITHM_RIGHT_ASYMMETRIC:
  			pd_idx = sector_div(stripe2, raid_disks);
  			if (*dd_idx >= pd_idx)
  				(*dd_idx)++;
  			break;
  		case ALGORITHM_LEFT_SYMMETRIC:
  			pd_idx = data_disks - sector_div(stripe2, raid_disks);
  			*dd_idx = (pd_idx + 1 + *dd_idx) % raid_disks;
  			break;
  		case ALGORITHM_RIGHT_SYMMETRIC:
  			pd_idx = sector_div(stripe2, raid_disks);
  			*dd_idx = (pd_idx + 1 + *dd_idx) % raid_disks;
  			break;
  		case ALGORITHM_PARITY_0:
  			pd_idx = 0;
  			(*dd_idx)++;
  			break;
  		case ALGORITHM_PARITY_N:
  			pd_idx = data_disks;
  			break;
  		default:
  			BUG();
  		}
  		break;
  	case 6:
  
  		switch (algorithm) {
  		case ALGORITHM_LEFT_ASYMMETRIC:
  			pd_idx = raid_disks - 1 - sector_div(stripe2, raid_disks);
  			qd_idx = pd_idx + 1;
  			if (pd_idx == raid_disks-1) {
  				(*dd_idx)++;	/* Q D D D P */
  				qd_idx = 0;
  			} else if (*dd_idx >= pd_idx)
  				(*dd_idx) += 2; /* D D P Q D */
  			break;
  		case ALGORITHM_RIGHT_ASYMMETRIC:
  			pd_idx = sector_div(stripe2, raid_disks);
  			qd_idx = pd_idx + 1;
  			if (pd_idx == raid_disks-1) {
  				(*dd_idx)++;	/* Q D D D P */
  				qd_idx = 0;
  			} else if (*dd_idx >= pd_idx)
  				(*dd_idx) += 2; /* D D P Q D */
  			break;
  		case ALGORITHM_LEFT_SYMMETRIC:
  			pd_idx = raid_disks - 1 - sector_div(stripe2, raid_disks);
  			qd_idx = (pd_idx + 1) % raid_disks;
  			*dd_idx = (pd_idx + 2 + *dd_idx) % raid_disks;
  			break;
  		case ALGORITHM_RIGHT_SYMMETRIC:
  			pd_idx = sector_div(stripe2, raid_disks);
  			qd_idx = (pd_idx + 1) % raid_disks;
  			*dd_idx = (pd_idx + 2 + *dd_idx) % raid_disks;
  			break;
  
  		case ALGORITHM_PARITY_0:
  			pd_idx = 0;
  			qd_idx = 1;
  			(*dd_idx) += 2;
  			break;
  		case ALGORITHM_PARITY_N:
  			pd_idx = data_disks;
  			qd_idx = data_disks + 1;
  			break;
  
  		case ALGORITHM_ROTATING_ZERO_RESTART:
  			/* Exactly the same as RIGHT_ASYMMETRIC, but or
  			 * of blocks for computing Q is different.
  			 */
  			pd_idx = sector_div(stripe2, raid_disks);
  			qd_idx = pd_idx + 1;
  			if (pd_idx == raid_disks-1) {
  				(*dd_idx)++;	/* Q D D D P */
  				qd_idx = 0;
  			} else if (*dd_idx >= pd_idx)
  				(*dd_idx) += 2; /* D D P Q D */
  			ddf_layout = 1;
  			break;
  
  		case ALGORITHM_ROTATING_N_RESTART:
  			/* Same a left_asymmetric, by first stripe is
  			 * D D D P Q  rather than
  			 * Q D D D P
  			 */
  			stripe2 += 1;
  			pd_idx = raid_disks - 1 - sector_div(stripe2, raid_disks);
  			qd_idx = pd_idx + 1;
  			if (pd_idx == raid_disks-1) {
  				(*dd_idx)++;	/* Q D D D P */
  				qd_idx = 0;
  			} else if (*dd_idx >= pd_idx)
  				(*dd_idx) += 2; /* D D P Q D */
  			ddf_layout = 1;
  			break;
  
  		case ALGORITHM_ROTATING_N_CONTINUE:
  			/* Same as left_symmetric but Q is before P */
  			pd_idx = raid_disks - 1 - sector_div(stripe2, raid_disks);
  			qd_idx = (pd_idx + raid_disks - 1) % raid_disks;
  			*dd_idx = (pd_idx + 1 + *dd_idx) % raid_disks;
  			ddf_layout = 1;
  			break;
  
  		case ALGORITHM_LEFT_ASYMMETRIC_6:
  			/* RAID5 left_asymmetric, with Q on last device */
  			pd_idx = data_disks - sector_div(stripe2, raid_disks-1);
  			if (*dd_idx >= pd_idx)
  				(*dd_idx)++;
  			qd_idx = raid_disks - 1;
  			break;
  
  		case ALGORITHM_RIGHT_ASYMMETRIC_6:
  			pd_idx = sector_div(stripe2, raid_disks-1);
  			if (*dd_idx >= pd_idx)
  				(*dd_idx)++;
  			qd_idx = raid_disks - 1;
  			break;
  
  		case ALGORITHM_LEFT_SYMMETRIC_6:
  			pd_idx = data_disks - sector_div(stripe2, raid_disks-1);
  			*dd_idx = (pd_idx + 1 + *dd_idx) % (raid_disks-1);
  			qd_idx = raid_disks - 1;
  			break;
  
  		case ALGORITHM_RIGHT_SYMMETRIC_6:
  			pd_idx = sector_div(stripe2, raid_disks-1);
  			*dd_idx = (pd_idx + 1 + *dd_idx) % (raid_disks-1);
  			qd_idx = raid_disks - 1;
  			break;
  
  		case ALGORITHM_PARITY_0_6:
  			pd_idx = 0;
  			(*dd_idx)++;
  			qd_idx = raid_disks - 1;
  			break;
  
  		default:
  			BUG();
  		}
  		break;
  	}
  
  	if (sh) {
  		sh->pd_idx = pd_idx;
  		sh->qd_idx = qd_idx;
  		sh->ddf_layout = ddf_layout;
  	}
  	/*
  	 * Finally, compute the new sector number
  	 */
  	new_sector = (sector_t)stripe * sectors_per_chunk + chunk_offset;
  	return new_sector;
  }
  
  sector_t raid5_compute_blocknr(struct stripe_head *sh, int i, int previous)
  {
  	struct r5conf *conf = sh->raid_conf;
  	int raid_disks = sh->disks;
  	int data_disks = raid_disks - conf->max_degraded;
  	sector_t new_sector = sh->sector, check;
  	int sectors_per_chunk = previous ? conf->prev_chunk_sectors
  					 : conf->chunk_sectors;
  	int algorithm = previous ? conf->prev_algo
  				 : conf->algorithm;
  	sector_t stripe;
  	int chunk_offset;
  	sector_t chunk_number;
  	int dummy1, dd_idx = i;
  	sector_t r_sector;
  	struct stripe_head sh2;
  
  	chunk_offset = sector_div(new_sector, sectors_per_chunk);
  	stripe = new_sector;
  
  	if (i == sh->pd_idx)
  		return 0;
  	switch(conf->level) {
  	case 4: break;
  	case 5:
  		switch (algorithm) {
  		case ALGORITHM_LEFT_ASYMMETRIC:
  		case ALGORITHM_RIGHT_ASYMMETRIC:
  			if (i > sh->pd_idx)
  				i--;
  			break;
  		case ALGORITHM_LEFT_SYMMETRIC:
  		case ALGORITHM_RIGHT_SYMMETRIC:
  			if (i < sh->pd_idx)
  				i += raid_disks;
  			i -= (sh->pd_idx + 1);
  			break;
  		case ALGORITHM_PARITY_0:
  			i -= 1;
  			break;
  		case ALGORITHM_PARITY_N:
  			break;
  		default:
  			BUG();
  		}
  		break;
  	case 6:
  		if (i == sh->qd_idx)
  			return 0; /* It is the Q disk */
  		switch (algorithm) {
  		case ALGORITHM_LEFT_ASYMMETRIC:
  		case ALGORITHM_RIGHT_ASYMMETRIC:
  		case ALGORITHM_ROTATING_ZERO_RESTART:
  		case ALGORITHM_ROTATING_N_RESTART:
  			if (sh->pd_idx == raid_disks-1)
  				i--;	/* Q D D D P */
  			else if (i > sh->pd_idx)
  				i -= 2; /* D D P Q D */
  			break;
  		case ALGORITHM_LEFT_SYMMETRIC:
  		case ALGORITHM_RIGHT_SYMMETRIC:
  			if (sh->pd_idx == raid_disks-1)
  				i--; /* Q D D D P */
  			else {
  				/* D D P Q D */
  				if (i < sh->pd_idx)
  					i += raid_disks;
  				i -= (sh->pd_idx + 2);
  			}
  			break;
  		case ALGORITHM_PARITY_0:
  			i -= 2;
  			break;
  		case ALGORITHM_PARITY_N:
  			break;
  		case ALGORITHM_ROTATING_N_CONTINUE:
  			/* Like left_symmetric, but P is before Q */
  			if (sh->pd_idx == 0)
  				i--;	/* P D D D Q */
  			else {
  				/* D D Q P D */
  				if (i < sh->pd_idx)
  					i += raid_disks;
  				i -= (sh->pd_idx + 1);
  			}
  			break;
  		case ALGORITHM_LEFT_ASYMMETRIC_6:
  		case ALGORITHM_RIGHT_ASYMMETRIC_6:
  			if (i > sh->pd_idx)
  				i--;
  			break;
  		case ALGORITHM_LEFT_SYMMETRIC_6:
  		case ALGORITHM_RIGHT_SYMMETRIC_6:
  			if (i < sh->pd_idx)
  				i += data_disks + 1;
  			i -= (sh->pd_idx + 1);
  			break;
  		case ALGORITHM_PARITY_0_6:
  			i -= 1;
  			break;
  		default:
  			BUG();
  		}
  		break;
  	}
  
  	chunk_number = stripe * data_disks + i;
  	r_sector = chunk_number * sectors_per_chunk + chunk_offset;
  
  	check = raid5_compute_sector(conf, r_sector,
  				     previous, &dummy1, &sh2);
  	if (check != sh->sector || dummy1 != dd_idx || sh2.pd_idx != sh->pd_idx
  		|| sh2.qd_idx != sh->qd_idx) {
  		pr_warn("md/raid:%s: compute_blocknr: map not correct\n",
  			mdname(conf->mddev));
  		return 0;
  	}
  	return r_sector;
  }
  
  /*
   * There are cases where we want handle_stripe_dirtying() and
   * schedule_reconstruction() to delay towrite to some dev of a stripe.
   *
   * This function checks whether we want to delay the towrite. Specifically,
   * we delay the towrite when:
   *
   *   1. degraded stripe has a non-overwrite to the missing dev, AND this
   *      stripe has data in journal (for other devices).
   *
   *      In this case, when reading data for the non-overwrite dev, it is
   *      necessary to handle complex rmw of write back cache (prexor with
   *      orig_page, and xor with page). To keep read path simple, we would
   *      like to flush data in journal to RAID disks first, so complex rmw
   *      is handled in the write patch (handle_stripe_dirtying).
   *
   *   2. when journal space is critical (R5C_LOG_CRITICAL=1)
   *
   *      It is important to be able to flush all stripes in raid5-cache.
   *      Therefore, we need reserve some space on the journal device for
   *      these flushes. If flush operation includes pending writes to the
   *      stripe, we need to reserve (conf->raid_disk + 1) pages per stripe
   *      for the flush out. If we exclude these pending writes from flush
   *      operation, we only need (conf->max_degraded + 1) pages per stripe.
   *      Therefore, excluding pending writes in these cases enables more
   *      efficient use of the journal device.
   *
   *      Note: To make sure the stripe makes progress, we only delay
   *      towrite for stripes with data already in journal (injournal > 0).
   *      When LOG_CRITICAL, stripes with injournal == 0 will be sent to
   *      no_space_stripes list.
   *
   *   3. during journal failure
   *      In journal failure, we try to flush all cached data to raid disks
   *      based on data in stripe cache. The array is read-only to upper
   *      layers, so we would skip all pending writes.
   *
   */
  static inline bool delay_towrite(struct r5conf *conf,
  				 struct r5dev *dev,
  				 struct stripe_head_state *s)
  {
  	/* case 1 above */
  	if (!test_bit(R5_OVERWRITE, &dev->flags) &&
  	    !test_bit(R5_Insync, &dev->flags) && s->injournal)
  		return true;
  	/* case 2 above */
  	if (test_bit(R5C_LOG_CRITICAL, &conf->cache_state) &&
  	    s->injournal > 0)
  		return true;
  	/* case 3 above */
  	if (s->log_failed && s->injournal)
  		return true;
  	return false;
  }
  
  static void
  schedule_reconstruction(struct stripe_head *sh, struct stripe_head_state *s,
  			 int rcw, int expand)
  {
  	int i, pd_idx = sh->pd_idx, qd_idx = sh->qd_idx, disks = sh->disks;
  	struct r5conf *conf = sh->raid_conf;
  	int level = conf->level;
  
  	if (rcw) {
  		/*
  		 * In some cases, handle_stripe_dirtying initially decided to
  		 * run rmw and allocates extra page for prexor. However, rcw is
  		 * cheaper later on. We need to free the extra page now,
  		 * because we won't be able to do that in ops_complete_prexor().
  		 */
  		r5c_release_extra_page(sh);
  
  		for (i = disks; i--; ) {
  			struct r5dev *dev = &sh->dev[i];
  
  			if (dev->towrite && !delay_towrite(conf, dev, s)) {
  				set_bit(R5_LOCKED, &dev->flags);
  				set_bit(R5_Wantdrain, &dev->flags);
  				if (!expand)
  					clear_bit(R5_UPTODATE, &dev->flags);
  				s->locked++;
  			} else if (test_bit(R5_InJournal, &dev->flags)) {
  				set_bit(R5_LOCKED, &dev->flags);
  				s->locked++;
  			}
  		}
  		/* if we are not expanding this is a proper write request, and
  		 * there will be bios with new data to be drained into the
  		 * stripe cache
  		 */
  		if (!expand) {
  			if (!s->locked)
  				/* False alarm, nothing to do */
  				return;
  			sh->reconstruct_state = reconstruct_state_drain_run;
  			set_bit(STRIPE_OP_BIODRAIN, &s->ops_request);
  		} else
  			sh->reconstruct_state = reconstruct_state_run;
  
  		set_bit(STRIPE_OP_RECONSTRUCT, &s->ops_request);
  
  		if (s->locked + conf->max_degraded == disks)
  			if (!test_and_set_bit(STRIPE_FULL_WRITE, &sh->state))
  				atomic_inc(&conf->pending_full_writes);
  	} else {
  		BUG_ON(!(test_bit(R5_UPTODATE, &sh->dev[pd_idx].flags) ||
  			test_bit(R5_Wantcompute, &sh->dev[pd_idx].flags)));
  		BUG_ON(level == 6 &&
  			(!(test_bit(R5_UPTODATE, &sh->dev[qd_idx].flags) ||
  			   test_bit(R5_Wantcompute, &sh->dev[qd_idx].flags))));
  
  		for (i = disks; i--; ) {
  			struct r5dev *dev = &sh->dev[i];
  			if (i == pd_idx || i == qd_idx)
  				continue;
  
  			if (dev->towrite &&
  			    (test_bit(R5_UPTODATE, &dev->flags) ||
  			     test_bit(R5_Wantcompute, &dev->flags))) {
  				set_bit(R5_Wantdrain, &dev->flags);
  				set_bit(R5_LOCKED, &dev->flags);
  				clear_bit(R5_UPTODATE, &dev->flags);
  				s->locked++;
  			} else if (test_bit(R5_InJournal, &dev->flags)) {
  				set_bit(R5_LOCKED, &dev->flags);
  				s->locked++;
  			}
  		}
  		if (!s->locked)
  			/* False alarm - nothing to do */
  			return;
  		sh->reconstruct_state = reconstruct_state_prexor_drain_run;
  		set_bit(STRIPE_OP_PREXOR, &s->ops_request);
  		set_bit(STRIPE_OP_BIODRAIN, &s->ops_request);
  		set_bit(STRIPE_OP_RECONSTRUCT, &s->ops_request);
  	}
  
  	/* keep the parity disk(s) locked while asynchronous operations
  	 * are in flight
  	 */
  	set_bit(R5_LOCKED, &sh->dev[pd_idx].flags);
  	clear_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
  	s->locked++;
  
  	if (level == 6) {
  		int qd_idx = sh->qd_idx;
  		struct r5dev *dev = &sh->dev[qd_idx];
  
  		set_bit(R5_LOCKED, &dev->flags);
  		clear_bit(R5_UPTODATE, &dev->flags);
  		s->locked++;
  	}
  
  	if (raid5_has_ppl(sh->raid_conf) && sh->ppl_page &&
  	    test_bit(STRIPE_OP_BIODRAIN, &s->ops_request) &&
  	    !test_bit(STRIPE_FULL_WRITE, &sh->state) &&
  	    test_bit(R5_Insync, &sh->dev[pd_idx].flags))
  		set_bit(STRIPE_OP_PARTIAL_PARITY, &s->ops_request);
  
  	pr_debug("%s: stripe %llu locked: %d ops_request: %lx\n",
  		__func__, (unsigned long long)sh->sector,
  		s->locked, s->ops_request);
  }
  
  /*
   * Each stripe/dev can have one or more bion attached.
   * toread/towrite point to the first in a chain.
   * The bi_next chain must be in order.
   */
  static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
  			  int forwrite, int previous)
  {
  	struct bio **bip;
  	struct r5conf *conf = sh->raid_conf;
  	int firstwrite=0;
  
  	pr_debug("adding bi b#%llu to stripe s#%llu\n",
  		(unsigned long long)bi->bi_iter.bi_sector,
  		(unsigned long long)sh->sector);
  
  	spin_lock_irq(&sh->stripe_lock);
  	sh->dev[dd_idx].write_hint = bi->bi_write_hint;
  	/* Don't allow new IO added to stripes in batch list */
  	if (sh->batch_head)
  		goto overlap;
  	if (forwrite) {
  		bip = &sh->dev[dd_idx].towrite;
  		if (*bip == NULL)
  			firstwrite = 1;
  	} else
  		bip = &sh->dev[dd_idx].toread;
  	while (*bip && (*bip)->bi_iter.bi_sector < bi->bi_iter.bi_sector) {
  		if (bio_end_sector(*bip) > bi->bi_iter.bi_sector)
  			goto overlap;
  		bip = & (*bip)->bi_next;
  	}
  	if (*bip && (*bip)->bi_iter.bi_sector < bio_end_sector(bi))
  		goto overlap;
  
  	if (forwrite && raid5_has_ppl(conf)) {
  		/*
  		 * With PPL only writes to consecutive data chunks within a
  		 * stripe are allowed because for a single stripe_head we can
  		 * only have one PPL entry at a time, which describes one data
  		 * range. Not really an overlap, but wait_for_overlap can be
  		 * used to handle this.
  		 */
  		sector_t sector;
  		sector_t first = 0;
  		sector_t last = 0;
  		int count = 0;
  		int i;
  
  		for (i = 0; i < sh->disks; i++) {
  			if (i != sh->pd_idx &&
  			    (i == dd_idx || sh->dev[i].towrite)) {
  				sector = sh->dev[i].sector;
  				if (count == 0 || sector < first)
  					first = sector;
  				if (sector > last)
  					last = sector;
  				count++;
  			}
  		}
  
  		if (first + conf->chunk_sectors * (count - 1) != last)
  			goto overlap;
  	}
  
  	if (!forwrite || previous)
  		clear_bit(STRIPE_BATCH_READY, &sh->state);
  
  	BUG_ON(*bip && bi->bi_next && (*bip) != bi->bi_next);
  	if (*bip)
  		bi->bi_next = *bip;
  	*bip = bi;
  	bio_inc_remaining(bi);
  	md_write_inc(conf->mddev, bi);
  
  	if (forwrite) {
  		/* check if page is covered */
  		sector_t sector = sh->dev[dd_idx].sector;
  		for (bi=sh->dev[dd_idx].towrite;
  		     sector < sh->dev[dd_idx].sector + RAID5_STRIPE_SECTORS(conf) &&
  			     bi && bi->bi_iter.bi_sector <= sector;
  		     bi = r5_next_bio(conf, bi, sh->dev[dd_idx].sector)) {
  			if (bio_end_sector(bi) >= sector)
  				sector = bio_end_sector(bi);
  		}
  		if (sector >= sh->dev[dd_idx].sector + RAID5_STRIPE_SECTORS(conf))
  			if (!test_and_set_bit(R5_OVERWRITE, &sh->dev[dd_idx].flags))
  				sh->overwrite_disks++;
  	}
  
  	pr_debug("added bi b#%llu to stripe s#%llu, disk %d.\n",
  		(unsigned long long)(*bip)->bi_iter.bi_sector,
  		(unsigned long long)sh->sector, dd_idx);
  
  	if (conf->mddev->bitmap && firstwrite) {
  		/* Cannot hold spinlock over bitmap_startwrite,
  		 * but must ensure this isn't added to a batch until
  		 * we have added to the bitmap and set bm_seq.
  		 * So set STRIPE_BITMAP_PENDING to prevent
  		 * batching.
  		 * If multiple add_stripe_bio() calls race here they
  		 * much all set STRIPE_BITMAP_PENDING.  So only the first one
  		 * to complete "bitmap_startwrite" gets to set
  		 * STRIPE_BIT_DELAY.  This is important as once a stripe
  		 * is added to a batch, STRIPE_BIT_DELAY cannot be changed
  		 * any more.
  		 */
  		set_bit(STRIPE_BITMAP_PENDING, &sh->state);
  		spin_unlock_irq(&sh->stripe_lock);
  		md_bitmap_startwrite(conf->mddev->bitmap, sh->sector,
  				     RAID5_STRIPE_SECTORS(conf), 0);
  		spin_lock_irq(&sh->stripe_lock);
  		clear_bit(STRIPE_BITMAP_PENDING, &sh->state);
  		if (!sh->batch_head) {
  			sh->bm_seq = conf->seq_flush+1;
  			set_bit(STRIPE_BIT_DELAY, &sh->state);
  		}
  	}
  	spin_unlock_irq(&sh->stripe_lock);
  
  	if (stripe_can_batch(sh))
  		stripe_add_to_batch_list(conf, sh);
  	return 1;
  
   overlap:
  	set_bit(R5_Overlap, &sh->dev[dd_idx].flags);
  	spin_unlock_irq(&sh->stripe_lock);
  	return 0;
  }
  
  static void end_reshape(struct r5conf *conf);
  
  static void stripe_set_idx(sector_t stripe, struct r5conf *conf, int previous,
  			    struct stripe_head *sh)
  {
  	int sectors_per_chunk =
  		previous ? conf->prev_chunk_sectors : conf->chunk_sectors;
  	int dd_idx;
  	int chunk_offset = sector_div(stripe, sectors_per_chunk);
  	int disks = previous ? conf->previous_raid_disks : conf->raid_disks;
  
  	raid5_compute_sector(conf,
  			     stripe * (disks - conf->max_degraded)
  			     *sectors_per_chunk + chunk_offset,
  			     previous,
  			     &dd_idx, sh);
  }
  
  static void
  handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
  		     struct stripe_head_state *s, int disks)
  {
  	int i;
  	BUG_ON(sh->batch_head);
  	for (i = disks; i--; ) {
  		struct bio *bi;
  		int bitmap_end = 0;
  
  		if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
  			struct md_rdev *rdev;
  			rcu_read_lock();
  			rdev = rcu_dereference(conf->disks[i].rdev);
  			if (rdev && test_bit(In_sync, &rdev->flags) &&
  			    !test_bit(Faulty, &rdev->flags))
  				atomic_inc(&rdev->nr_pending);
  			else
  				rdev = NULL;
  			rcu_read_unlock();
  			if (rdev) {
  				if (!rdev_set_badblocks(
  					    rdev,
  					    sh->sector,
  					    RAID5_STRIPE_SECTORS(conf), 0))
  					md_error(conf->mddev, rdev);
  				rdev_dec_pending(rdev, conf->mddev);
  			}
  		}
  		spin_lock_irq(&sh->stripe_lock);
  		/* fail all writes first */
  		bi = sh->dev[i].towrite;
  		sh->dev[i].towrite = NULL;
  		sh->overwrite_disks = 0;
  		spin_unlock_irq(&sh->stripe_lock);
  		if (bi)
  			bitmap_end = 1;
  
  		log_stripe_write_finished(sh);
  
  		if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
  			wake_up(&conf->wait_for_overlap);
  
  		while (bi && bi->bi_iter.bi_sector <
  			sh->dev[i].sector + RAID5_STRIPE_SECTORS(conf)) {
  			struct bio *nextbi = r5_next_bio(conf, bi, sh->dev[i].sector);
  
  			md_write_end(conf->mddev);
  			bio_io_error(bi);
  			bi = nextbi;
  		}
  		if (bitmap_end)
  			md_bitmap_endwrite(conf->mddev->bitmap, sh->sector,
  					   RAID5_STRIPE_SECTORS(conf), 0, 0);
  		bitmap_end = 0;
  		/* and fail all 'written' */
  		bi = sh->dev[i].written;
  		sh->dev[i].written = NULL;
  		if (test_and_clear_bit(R5_SkipCopy, &sh->dev[i].flags)) {
  			WARN_ON(test_bit(R5_UPTODATE, &sh->dev[i].flags));
  			sh->dev[i].page = sh->dev[i].orig_page;
  		}
  
  		if (bi) bitmap_end = 1;
  		while (bi && bi->bi_iter.bi_sector <
  		       sh->dev[i].sector + RAID5_STRIPE_SECTORS(conf)) {
  			struct bio *bi2 = r5_next_bio(conf, bi, sh->dev[i].sector);
  
  			md_write_end(conf->mddev);
  			bio_io_error(bi);
  			bi = bi2;
  		}
  
  		/* fail any reads if this device is non-operational and
  		 * the data has not reached the cache yet.
  		 */
  		if (!test_bit(R5_Wantfill, &sh->dev[i].flags) &&
  		    s->failed > conf->max_degraded &&
  		    (!test_bit(R5_Insync, &sh->dev[i].flags) ||
  		      test_bit(R5_ReadError, &sh->dev[i].flags))) {
  			spin_lock_irq(&sh->stripe_lock);
  			bi = sh->dev[i].toread;
  			sh->dev[i].toread = NULL;
  			spin_unlock_irq(&sh->stripe_lock);
  			if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
  				wake_up(&conf->wait_for_overlap);
  			if (bi)
  				s->to_read--;
  			while (bi && bi->bi_iter.bi_sector <
  			       sh->dev[i].sector + RAID5_STRIPE_SECTORS(conf)) {
  				struct bio *nextbi =
  					r5_next_bio(conf, bi, sh->dev[i].sector);
  
  				bio_io_error(bi);
  				bi = nextbi;
  			}
  		}
  		if (bitmap_end)
  			md_bitmap_endwrite(conf->mddev->bitmap, sh->sector,
  					   RAID5_STRIPE_SECTORS(conf), 0, 0);
  		/* If we were in the middle of a write the parity block might
  		 * still be locked - so just clear all R5_LOCKED flags
  		 */
  		clear_bit(R5_LOCKED, &sh->dev[i].flags);
  	}
  	s->to_write = 0;
  	s->written = 0;
  
  	if (test_and_clear_bit(STRIPE_FULL_WRITE, &sh->state))
  		if (atomic_dec_and_test(&conf->pending_full_writes))
  			md_wakeup_thread(conf->mddev->thread);
  }
  
  static void
  handle_failed_sync(struct r5conf *conf, struct stripe_head *sh,
  		   struct stripe_head_state *s)
  {
  	int abort = 0;
  	int i;
  
  	BUG_ON(sh->batch_head);
  	clear_bit(STRIPE_SYNCING, &sh->state);
  	if (test_and_clear_bit(R5_Overlap, &sh->dev[sh->pd_idx].flags))
  		wake_up(&conf->wait_for_overlap);
  	s->syncing = 0;
  	s->replacing = 0;
  	/* There is nothing more to do for sync/check/repair.
  	 * Don't even need to abort as that is handled elsewhere
  	 * if needed, and not always wanted e.g. if there is a known
  	 * bad block here.
  	 * For recover/replace we need to record a bad block on all
  	 * non-sync devices, or abort the recovery
  	 */
  	if (test_bit(MD_RECOVERY_RECOVER, &conf->mddev->recovery)) {
  		/* During recovery devices cannot be removed, so
  		 * locking and refcounting of rdevs is not needed
  		 */
  		rcu_read_lock();
  		for (i = 0; i < conf->raid_disks; i++) {
  			struct md_rdev *rdev = rcu_dereference(conf->disks[i].rdev);
  			if (rdev
  			    && !test_bit(Faulty, &rdev->flags)
  			    && !test_bit(In_sync, &rdev->flags)
  			    && !rdev_set_badblocks(rdev, sh->sector,
  						   RAID5_STRIPE_SECTORS(conf), 0))
  				abort = 1;
  			rdev = rcu_dereference(conf->disks[i].replacement);
  			if (rdev
  			    && !test_bit(Faulty, &rdev->flags)
  			    && !test_bit(In_sync, &rdev->flags)
  			    && !rdev_set_badblocks(rdev, sh->sector,
  						   RAID5_STRIPE_SECTORS(conf), 0))
  				abort = 1;
  		}
  		rcu_read_unlock();
  		if (abort)
  			conf->recovery_disabled =
  				conf->mddev->recovery_disabled;
  	}
  	md_done_sync(conf->mddev, RAID5_STRIPE_SECTORS(conf), !abort);
  }
  
  static int want_replace(struct stripe_head *sh, int disk_idx)
  {
  	struct md_rdev *rdev;
  	int rv = 0;
  
  	rcu_read_lock();
  	rdev = rcu_dereference(sh->raid_conf->disks[disk_idx].replacement);
  	if (rdev
  	    && !test_bit(Faulty, &rdev->flags)
  	    && !test_bit(In_sync, &rdev->flags)
  	    && (rdev->recovery_offset <= sh->sector
  		|| rdev->mddev->recovery_cp <= sh->sector))
  		rv = 1;
  	rcu_read_unlock();
  	return rv;
  }
  
  static int need_this_block(struct stripe_head *sh, struct stripe_head_state *s,
  			   int disk_idx, int disks)
  {
  	struct r5dev *dev = &sh->dev[disk_idx];
  	struct r5dev *fdev[2] = { &sh->dev[s->failed_num[0]],
  				  &sh->dev[s->failed_num[1]] };
  	int i;
  	bool force_rcw = (sh->raid_conf->rmw_level == PARITY_DISABLE_RMW);
  
  
  	if (test_bit(R5_LOCKED, &dev->flags) ||
  	    test_bit(R5_UPTODATE, &dev->flags))
  		/* No point reading this as we already have it or have
  		 * decided to get it.
  		 */
  		return 0;
  
  	if (dev->toread ||
  	    (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)))
  		/* We need this block to directly satisfy a request */
  		return 1;
  
  	if (s->syncing || s->expanding ||
  	    (s->replacing && want_replace(sh, disk_idx)))
  		/* When syncing, or expanding we read everything.
  		 * When replacing, we need the replaced block.
  		 */
  		return 1;
  
  	if ((s->failed >= 1 && fdev[0]->toread) ||
  	    (s->failed >= 2 && fdev[1]->toread))
  		/* If we want to read from a failed device, then
  		 * we need to actually read every other device.
  		 */
  		return 1;
  
  	/* Sometimes neither read-modify-write nor reconstruct-write
  	 * cycles can work.  In those cases we read every block we
  	 * can.  Then the parity-update is certain to have enough to
  	 * work with.
  	 * This can only be a problem when we need to write something,
  	 * and some device has failed.  If either of those tests
  	 * fail we need look no further.
  	 */
  	if (!s->failed || !s->to_write)
  		return 0;
  
  	if (test_bit(R5_Insync, &dev->flags) &&
  	    !test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
  		/* Pre-reads at not permitted until after short delay
  		 * to gather multiple requests.  However if this
  		 * device is no Insync, the block could only be computed
  		 * and there is no need to delay that.
  		 */
  		return 0;
  
  	for (i = 0; i < s->failed && i < 2; i++) {
  		if (fdev[i]->towrite &&
  		    !test_bit(R5_UPTODATE, &fdev[i]->flags) &&
  		    !test_bit(R5_OVERWRITE, &fdev[i]->flags))
  			/* If we have a partial write to a failed
  			 * device, then we will need to reconstruct
  			 * the content of that device, so all other
  			 * devices must be read.
  			 */
  			return 1;
  
  		if (s->failed >= 2 &&
  		    (fdev[i]->towrite ||
  		     s->failed_num[i] == sh->pd_idx ||
  		     s->failed_num[i] == sh->qd_idx) &&
  		    !test_bit(R5_UPTODATE, &fdev[i]->flags))
  			/* In max degraded raid6, If the failed disk is P, Q,
  			 * or we want to read the failed disk, we need to do
  			 * reconstruct-write.
  			 */
  			force_rcw = true;
  	}
  
  	/* If we are forced to do a reconstruct-write, because parity
  	 * cannot be trusted and we are currently recovering it, there
  	 * is extra need to be careful.
  	 * If one of the devices that we would need to read, because
  	 * it is not being overwritten (and maybe not written at all)
  	 * is missing/faulty, then we need to read everything we can.
  	 */
  	if (!force_rcw &&
  	    sh->sector < sh->raid_conf->mddev->recovery_cp)
  		/* reconstruct-write isn't being forced */
  		return 0;
  	for (i = 0; i < s->failed && i < 2; i++) {
  		if (s->failed_num[i] != sh->pd_idx &&
  		    s->failed_num[i] != sh->qd_idx &&
  		    !test_bit(R5_UPTODATE, &fdev[i]->flags) &&
  		    !test_bit(R5_OVERWRITE, &fdev[i]->flags))
  			return 1;
  	}
  
  	return 0;
  }
  
  /* fetch_block - checks the given member device to see if its data needs
   * to be read or computed to satisfy a request.
   *
   * Returns 1 when no more member devices need to be checked, otherwise returns
   * 0 to tell the loop in handle_stripe_fill to continue
   */
  static int fetch_block(struct stripe_head *sh, struct stripe_head_state *s,
  		       int disk_idx, int disks)
  {
  	struct r5dev *dev = &sh->dev[disk_idx];
  
  	/* is the data in this block needed, and can we get it? */
  	if (need_this_block(sh, s, disk_idx, disks)) {
  		/* we would like to get this block, possibly by computing it,
  		 * otherwise read it if the backing disk is insync
  		 */
  		BUG_ON(test_bit(R5_Wantcompute, &dev->flags));
  		BUG_ON(test_bit(R5_Wantread, &dev->flags));
  		BUG_ON(sh->batch_head);
  
  		/*
  		 * In the raid6 case if the only non-uptodate disk is P
  		 * then we already trusted P to compute the other failed
  		 * drives. It is safe to compute rather than re-read P.
  		 * In other cases we only compute blocks from failed
  		 * devices, otherwise check/repair might fail to detect
  		 * a real inconsistency.
  		 */
  
  		if ((s->uptodate == disks - 1) &&
  		    ((sh->qd_idx >= 0 && sh->pd_idx == disk_idx) ||
  		    (s->failed && (disk_idx == s->failed_num[0] ||
  				   disk_idx == s->failed_num[1])))) {
  			/* have disk failed, and we're requested to fetch it;
  			 * do compute it
  			 */
  			pr_debug("Computing stripe %llu block %d\n",
  			       (unsigned long long)sh->sector, disk_idx);
  			set_bit(STRIPE_COMPUTE_RUN, &sh->state);
  			set_bit(STRIPE_OP_COMPUTE_BLK, &s->ops_request);
  			set_bit(R5_Wantcompute, &dev->flags);
  			sh->ops.target = disk_idx;
  			sh->ops.target2 = -1; /* no 2nd target */
  			s->req_compute = 1;
  			/* Careful: from this point on 'uptodate' is in the eye
  			 * of raid_run_ops which services 'compute' operations
  			 * before writes. R5_Wantcompute flags a block that will
  			 * be R5_UPTODATE by the time it is needed for a
  			 * subsequent operation.
  			 */
  			s->uptodate++;
  			return 1;
  		} else if (s->uptodate == disks-2 && s->failed >= 2) {
  			/* Computing 2-failure is *very* expensive; only
  			 * do it if failed >= 2
  			 */
  			int other;
  			for (other = disks; other--; ) {
  				if (other == disk_idx)
  					continue;
  				if (!test_bit(R5_UPTODATE,
  				      &sh->dev[other].flags))
  					break;
  			}
  			BUG_ON(other < 0);
  			pr_debug("Computing stripe %llu blocks %d,%d\n",
  			       (unsigned long long)sh->sector,
  			       disk_idx, other);
  			set_bit(STRIPE_COMPUTE_RUN, &sh->state);
  			set_bit(STRIPE_OP_COMPUTE_BLK, &s->ops_request);
  			set_bit(R5_Wantcompute, &sh->dev[disk_idx].flags);
  			set_bit(R5_Wantcompute, &sh->dev[other].flags);
  			sh->ops.target = disk_idx;
  			sh->ops.target2 = other;
  			s->uptodate += 2;
  			s->req_compute = 1;
  			return 1;
  		} else if (test_bit(R5_Insync, &dev->flags)) {
  			set_bit(R5_LOCKED, &dev->flags);
  			set_bit(R5_Wantread, &dev->flags);
  			s->locked++;
  			pr_debug("Reading block %d (sync=%d)\n",
  				disk_idx, s->syncing);
  		}
  	}
  
  	return 0;
  }
  
  /*
   * handle_stripe_fill - read or compute data to satisfy pending requests.
   */
  static void handle_stripe_fill(struct stripe_head *sh,
  			       struct stripe_head_state *s,
  			       int disks)
  {
  	int i;
  
  	/* look for blocks to read/compute, skip this if a compute
  	 * is already in flight, or if the stripe contents are in the
  	 * midst of changing due to a write
  	 */
  	if (!test_bit(STRIPE_COMPUTE_RUN, &sh->state) && !sh->check_state &&
  	    !sh->reconstruct_state) {
  
  		/*
  		 * For degraded stripe with data in journal, do not handle
  		 * read requests yet, instead, flush the stripe to raid
  		 * disks first, this avoids handling complex rmw of write
  		 * back cache (prexor with orig_page, and then xor with
  		 * page) in the read path
  		 */
  		if (s->injournal && s->failed) {
  			if (test_bit(STRIPE_R5C_CACHING, &sh->state))
  				r5c_make_stripe_write_out(sh);
  			goto out;
  		}
  
  		for (i = disks; i--; )
  			if (fetch_block(sh, s, i, disks))
  				break;
  	}
  out:
  	set_bit(STRIPE_HANDLE, &sh->state);
  }
  
  static void break_stripe_batch_list(struct stripe_head *head_sh,
  				    unsigned long handle_flags);
  /* handle_stripe_clean_event
   * any written block on an uptodate or failed drive can be returned.
   * Note that if we 'wrote' to a failed drive, it will be UPTODATE, but
   * never LOCKED, so we don't need to test 'failed' directly.
   */
  static void handle_stripe_clean_event(struct r5conf *conf,
  	struct stripe_head *sh, int disks)
  {
  	int i;
  	struct r5dev *dev;
  	int discard_pending = 0;
  	struct stripe_head *head_sh = sh;
  	bool do_endio = false;
  
  	for (i = disks; i--; )
  		if (sh->dev[i].written) {
  			dev = &sh->dev[i];
  			if (!test_bit(R5_LOCKED, &dev->flags) &&
  			    (test_bit(R5_UPTODATE, &dev->flags) ||
  			     test_bit(R5_Discard, &dev->flags) ||
  			     test_bit(R5_SkipCopy, &dev->flags))) {
  				/* We can return any write requests */
  				struct bio *wbi, *wbi2;
  				pr_debug("Return write for disc %d\n", i);
  				if (test_and_clear_bit(R5_Discard, &dev->flags))
  					clear_bit(R5_UPTODATE, &dev->flags);
  				if (test_and_clear_bit(R5_SkipCopy, &dev->flags)) {
  					WARN_ON(test_bit(R5_UPTODATE, &dev->flags));
  				}
  				do_endio = true;
  
  returnbi:
  				dev->page = dev->orig_page;
  				wbi = dev->written;
  				dev->written = NULL;
  				while (wbi && wbi->bi_iter.bi_sector <
  					dev->sector + RAID5_STRIPE_SECTORS(conf)) {
  					wbi2 = r5_next_bio(conf, wbi, dev->sector);
  					md_write_end(conf->mddev);
  					bio_endio(wbi);
  					wbi = wbi2;
  				}
  				md_bitmap_endwrite(conf->mddev->bitmap, sh->sector,
  						   RAID5_STRIPE_SECTORS(conf),
  						   !test_bit(STRIPE_DEGRADED, &sh->state),
  						   0);
  				if (head_sh->batch_head) {
  					sh = list_first_entry(&sh->batch_list,
  							      struct stripe_head,
  							      batch_list);
  					if (sh != head_sh) {
  						dev = &sh->dev[i];
  						goto returnbi;
  					}
  				}
  				sh = head_sh;
  				dev = &sh->dev[i];
  			} else if (test_bit(R5_Discard, &dev->flags))
  				discard_pending = 1;
  		}
  
  	log_stripe_write_finished(sh);
  
  	if (!discard_pending &&
  	    test_bit(R5_Discard, &sh->dev[sh->pd_idx].flags)) {
  		int hash;
  		clear_bit(R5_Discard, &sh->dev[sh->pd_idx].flags);
  		clear_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags);
  		if (sh->qd_idx >= 0) {
  			clear_bit(R5_Discard, &sh->dev[sh->qd_idx].flags);
  			clear_bit(R5_UPTODATE, &sh->dev[sh->qd_idx].flags);
  		}
  		/* now that discard is done we can proceed with any sync */
  		clear_bit(STRIPE_DISCARD, &sh->state);
  		/*
  		 * SCSI discard will change some bio fields and the stripe has
  		 * no updated data, so remove it from hash list and the stripe
  		 * will be reinitialized
  		 */
  unhash:
  		hash = sh->hash_lock_index;
  		spin_lock_irq(conf->hash_locks + hash);
  		remove_hash(sh);
  		spin_unlock_irq(conf->hash_locks + hash);
  		if (head_sh->batch_head) {
  			sh = list_first_entry(&sh->batch_list,
  					      struct stripe_head, batch_list);
  			if (sh != head_sh)
  					goto unhash;
  		}
  		sh = head_sh;
  
  		if (test_bit(STRIPE_SYNC_REQUESTED, &sh->state))
  			set_bit(STRIPE_HANDLE, &sh->state);
  
  	}
  
  	if (test_and_clear_bit(STRIPE_FULL_WRITE, &sh->state))
  		if (atomic_dec_and_test(&conf->pending_full_writes))
  			md_wakeup_thread(conf->mddev->thread);
  
  	if (head_sh->batch_head && do_endio)
  		break_stripe_batch_list(head_sh, STRIPE_EXPAND_SYNC_FLAGS);
  }
  
  /*
   * For RMW in write back cache, we need extra page in prexor to store the
   * old data. This page is stored in dev->orig_page.
   *
   * This function checks whether we have data for prexor. The exact logic
   * is:
   *       R5_UPTODATE && (!R5_InJournal || R5_OrigPageUPTDODATE)
   */
  static inline bool uptodate_for_rmw(struct r5dev *dev)
  {
  	return (test_bit(R5_UPTODATE, &dev->flags)) &&
  		(!test_bit(R5_InJournal, &dev->flags) ||
  		 test_bit(R5_OrigPageUPTDODATE, &dev->flags));
  }
  
  static int handle_stripe_dirtying(struct r5conf *conf,
  				  struct stripe_head *sh,
  				  struct stripe_head_state *s,
  				  int disks)
  {
  	int rmw = 0, rcw = 0, i;
  	sector_t recovery_cp = conf->mddev->recovery_cp;
  
  	/* Check whether resync is now happening or should start.
  	 * If yes, then the array is dirty (after unclean shutdown or
  	 * initial creation), so parity in some stripes might be inconsistent.
  	 * In this case, we need to always do reconstruct-write, to ensure
  	 * that in case of drive failure or read-error correction, we
  	 * generate correct data from the parity.
  	 */
  	if (conf->rmw_level == PARITY_DISABLE_RMW ||
  	    (recovery_cp < MaxSector && sh->sector >= recovery_cp &&
  	     s->failed == 0)) {
  		/* Calculate the real rcw later - for now make it
  		 * look like rcw is cheaper
  		 */
  		rcw = 1; rmw = 2;
  		pr_debug("force RCW rmw_level=%u, recovery_cp=%llu sh->sector=%llu\n",
  			 conf->rmw_level, (unsigned long long)recovery_cp,
  			 (unsigned long long)sh->sector);
  	} else for (i = disks; i--; ) {
  		/* would I have to read this buffer for read_modify_write */
  		struct r5dev *dev = &sh->dev[i];
  		if (((dev->towrite && !delay_towrite(conf, dev, s)) ||
  		     i == sh->pd_idx || i == sh->qd_idx ||
  		     test_bit(R5_InJournal, &dev->flags)) &&
  		    !test_bit(R5_LOCKED, &dev->flags) &&
  		    !(uptodate_for_rmw(dev) ||
  		      test_bit(R5_Wantcompute, &dev->flags))) {
  			if (test_bit(R5_Insync, &dev->flags))
  				rmw++;
  			else
  				rmw += 2*disks;  /* cannot read it */
  		}
  		/* Would I have to read this buffer for reconstruct_write */
  		if (!test_bit(R5_OVERWRITE, &dev->flags) &&
  		    i != sh->pd_idx && i != sh->qd_idx &&
  		    !test_bit(R5_LOCKED, &dev->flags) &&
  		    !(test_bit(R5_UPTODATE, &dev->flags) ||
  		      test_bit(R5_Wantcompute, &dev->flags))) {
  			if (test_bit(R5_Insync, &dev->flags))
  				rcw++;
  			else
  				rcw += 2*disks;
  		}
  	}
  
  	pr_debug("for sector %llu state 0x%lx, rmw=%d rcw=%d\n",
  		 (unsigned long long)sh->sector, sh->state, rmw, rcw);
  	set_bit(STRIPE_HANDLE, &sh->state);
  	if ((rmw < rcw || (rmw == rcw && conf->rmw_level == PARITY_PREFER_RMW)) && rmw > 0) {
  		/* prefer read-modify-write, but need to get some data */
  		if (conf->mddev->queue)
  			blk_add_trace_msg(conf->mddev->queue,
  					  "raid5 rmw %llu %d",
  					  (unsigned long long)sh->sector, rmw);
  		for (i = disks; i--; ) {
  			struct r5dev *dev = &sh->dev[i];
  			if (test_bit(R5_InJournal, &dev->flags) &&
  			    dev->page == dev->orig_page &&
  			    !test_bit(R5_LOCKED, &sh->dev[sh->pd_idx].flags)) {
  				/* alloc page for prexor */
  				struct page *p = alloc_page(GFP_NOIO);
  
  				if (p) {
  					dev->orig_page = p;
  					continue;
  				}
  
  				/*
  				 * alloc_page() failed, try use
  				 * disk_info->extra_page
  				 */
  				if (!test_and_set_bit(R5C_EXTRA_PAGE_IN_USE,
  						      &conf->cache_state)) {
  					r5c_use_extra_page(sh);
  					break;
  				}
  
  				/* extra_page in use, add to delayed_list */
  				set_bit(STRIPE_DELAYED, &sh->state);
  				s->waiting_extra_page = 1;
  				return -EAGAIN;
  			}
  		}
  
  		for (i = disks; i--; ) {
  			struct r5dev *dev = &sh->dev[i];
  			if (((dev->towrite && !delay_towrite(conf, dev, s)) ||
  			     i == sh->pd_idx || i == sh->qd_idx ||
  			     test_bit(R5_InJournal, &dev->flags)) &&
  			    !test_bit(R5_LOCKED, &dev->flags) &&
  			    !(uptodate_for_rmw(dev) ||
  			      test_bit(R5_Wantcompute, &dev->flags)) &&
  			    test_bit(R5_Insync, &dev->flags)) {
  				if (test_bit(STRIPE_PREREAD_ACTIVE,
  					     &sh->state)) {
  					pr_debug("Read_old block %d for r-m-w\n",
  						 i);
  					set_bit(R5_LOCKED, &dev->flags);
  					set_bit(R5_Wantread, &dev->flags);
  					s->locked++;
  				} else
  					set_bit(STRIPE_DELAYED, &sh->state);
  			}
  		}
  	}
  	if ((rcw < rmw || (rcw == rmw && conf->rmw_level != PARITY_PREFER_RMW)) && rcw > 0) {
  		/* want reconstruct write, but need to get some data */
  		int qread =0;
  		rcw = 0;
  		for (i = disks; i--; ) {
  			struct r5dev *dev = &sh->dev[i];
  			if (!test_bit(R5_OVERWRITE, &dev->flags) &&
  			    i != sh->pd_idx && i != sh->qd_idx &&
  			    !test_bit(R5_LOCKED, &dev->flags) &&
  			    !(test_bit(R5_UPTODATE, &dev->flags) ||
  			      test_bit(R5_Wantcompute, &dev->flags))) {
  				rcw++;
  				if (test_bit(R5_Insync, &dev->flags) &&
  				    test_bit(STRIPE_PREREAD_ACTIVE,
  					     &sh->state)) {
  					pr_debug("Read_old block "
  						"%d for Reconstruct\n", i);
  					set_bit(R5_LOCKED, &dev->flags);
  					set_bit(R5_Wantread, &dev->flags);
  					s->locked++;
  					qread++;
  				} else
  					set_bit(STRIPE_DELAYED, &sh->state);
  			}
  		}
  		if (rcw && conf->mddev->queue)
  			blk_add_trace_msg(conf->mddev->queue, "raid5 rcw %llu %d %d %d",
  					  (unsigned long long)sh->sector,
  					  rcw, qread, test_bit(STRIPE_DELAYED, &sh->state));
  	}
  
  	if (rcw > disks && rmw > disks &&
  	    !test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
  		set_bit(STRIPE_DELAYED, &sh->state);
  
  	/* now if nothing is locked, and if we have enough data,
  	 * we can start a write request
  	 */
  	/* since handle_stripe can be called at any time we need to handle the
  	 * case where a compute block operation has been submitted and then a
  	 * subsequent call wants to start a write request.  raid_run_ops only
  	 * handles the case where compute block and reconstruct are requested
  	 * simultaneously.  If this is not the case then new writes need to be
  	 * held off until the compute completes.
  	 */
  	if ((s->req_compute || !test_bit(STRIPE_COMPUTE_RUN, &sh->state)) &&
  	    (s->locked == 0 && (rcw == 0 || rmw == 0) &&
  	     !test_bit(STRIPE_BIT_DELAY, &sh->state)))
  		schedule_reconstruction(sh, s, rcw == 0, 0);
  	return 0;
  }
  
  static void handle_parity_checks5(struct r5conf *conf, struct stripe_head *sh,
  				struct stripe_head_state *s, int disks)
  {
  	struct r5dev *dev = NULL;
  
  	BUG_ON(sh->batch_head);
  	set_bit(STRIPE_HANDLE, &sh->state);
  
  	switch (sh->check_state) {
  	case check_state_idle:
  		/* start a new check operation if there are no failures */
  		if (s->failed == 0) {
  			BUG_ON(s->uptodate != disks);
  			sh->check_state = check_state_run;
  			set_bit(STRIPE_OP_CHECK, &s->ops_request);
  			clear_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags);
  			s->uptodate--;
  			break;
  		}
  		dev = &sh->dev[s->failed_num[0]];
  		fallthrough;
  	case check_state_compute_result:
  		sh->check_state = check_state_idle;
  		if (!dev)
  			dev = &sh->dev[sh->pd_idx];
  
  		/* check that a write has not made the stripe insync */
  		if (test_bit(STRIPE_INSYNC, &sh->state))
  			break;
  
  		/* either failed parity check, or recovery is happening */
  		BUG_ON(!test_bit(R5_UPTODATE, &dev->flags));
  		BUG_ON(s->uptodate != disks);
  
  		set_bit(R5_LOCKED, &dev->flags);
  		s->locked++;
  		set_bit(R5_Wantwrite, &dev->flags);
  
  		clear_bit(STRIPE_DEGRADED, &sh->state);
  		set_bit(STRIPE_INSYNC, &sh->state);
  		break;
  	case check_state_run:
  		break; /* we will be called again upon completion */
  	case check_state_check_result:
  		sh->check_state = check_state_idle;
  
  		/* if a failure occurred during the check operation, leave
  		 * STRIPE_INSYNC not set and let the stripe be handled again
  		 */
  		if (s->failed)
  			break;
  
  		/* handle a successful check operation, if parity is correct
  		 * we are done.  Otherwise update the mismatch count and repair
  		 * parity if !MD_RECOVERY_CHECK
  		 */
  		if ((sh->ops.zero_sum_result & SUM_CHECK_P_RESULT) == 0)
  			/* parity is correct (on disc,
  			 * not in buffer any more)
  			 */
  			set_bit(STRIPE_INSYNC, &sh->state);
  		else {
  			atomic64_add(RAID5_STRIPE_SECTORS(conf), &conf->mddev->resync_mismatches);
  			if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery)) {
  				/* don't try to repair!! */
  				set_bit(STRIPE_INSYNC, &sh->state);
  				pr_warn_ratelimited("%s: mismatch sector in range "
  						    "%llu-%llu\n", mdname(conf->mddev),
  						    (unsigned long long) sh->sector,
  						    (unsigned long long) sh->sector +
  						    RAID5_STRIPE_SECTORS(conf));
  			} else {
  				sh->check_state = check_state_compute_run;
  				set_bit(STRIPE_COMPUTE_RUN, &sh->state);
  				set_bit(STRIPE_OP_COMPUTE_BLK, &s->ops_request);
  				set_bit(R5_Wantcompute,
  					&sh->dev[sh->pd_idx].flags);
  				sh->ops.target = sh->pd_idx;
  				sh->ops.target2 = -1;
  				s->uptodate++;
  			}
  		}
  		break;
  	case check_state_compute_run:
  		break;
  	default:
  		pr_err("%s: unknown check_state: %d sector: %llu\n",
  		       __func__, sh->check_state,
  		       (unsigned long long) sh->sector);
  		BUG();
  	}
  }
  
  static void handle_parity_checks6(struct r5conf *conf, struct stripe_head *sh,
  				  struct stripe_head_state *s,
  				  int disks)
  {
  	int pd_idx = sh->pd_idx;
  	int qd_idx = sh->qd_idx;
  	struct r5dev *dev;
  
  	BUG_ON(sh->batch_head);
  	set_bit(STRIPE_HANDLE, &sh->state);
  
  	BUG_ON(s->failed > 2);
  
  	/* Want to check and possibly repair P and Q.
  	 * However there could be one 'failed' device, in which
  	 * case we can only check one of them, possibly using the
  	 * other to generate missing data
  	 */
  
  	switch (sh->check_state) {
  	case check_state_idle:
  		/* start a new check operation if there are < 2 failures */
  		if (s->failed == s->q_failed) {
  			/* The only possible failed device holds Q, so it
  			 * makes sense to check P (If anything else were failed,
  			 * we would have used P to recreate it).
  			 */
  			sh->check_state = check_state_run;
  		}
  		if (!s->q_failed && s->failed < 2) {
  			/* Q is not failed, and we didn't use it to generate
  			 * anything, so it makes sense to check it
  			 */
  			if (sh->check_state == check_state_run)
  				sh->check_state = check_state_run_pq;
  			else
  				sh->check_state = check_state_run_q;
  		}
  
  		/* discard potentially stale zero_sum_result */
  		sh->ops.zero_sum_result = 0;
  
  		if (sh->check_state == check_state_run) {
  			/* async_xor_zero_sum destroys the contents of P */
  			clear_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
  			s->uptodate--;
  		}
  		if (sh->check_state >= check_state_run &&
  		    sh->check_state <= check_state_run_pq) {
  			/* async_syndrome_zero_sum preserves P and Q, so
  			 * no need to mark them !uptodate here
  			 */
  			set_bit(STRIPE_OP_CHECK, &s->ops_request);
  			break;
  		}
  
  		/* we have 2-disk failure */
  		BUG_ON(s->failed != 2);
  		fallthrough;
  	case check_state_compute_result:
  		sh->check_state = check_state_idle;
  
  		/* check that a write has not made the stripe insync */
  		if (test_bit(STRIPE_INSYNC, &sh->state))
  			break;
  
  		/* now write out any block on a failed drive,
  		 * or P or Q if they were recomputed
  		 */
  		dev = NULL;
  		if (s->failed == 2) {
  			dev = &sh->dev[s->failed_num[1]];
  			s->locked++;
  			set_bit(R5_LOCKED, &dev->flags);
  			set_bit(R5_Wantwrite, &dev->flags);
  		}
  		if (s->failed >= 1) {
  			dev = &sh->dev[s->failed_num[0]];
  			s->locked++;
  			set_bit(R5_LOCKED, &dev->flags);
  			set_bit(R5_Wantwrite, &dev->flags);
  		}
  		if (sh->ops.zero_sum_result & SUM_CHECK_P_RESULT) {
  			dev = &sh->dev[pd_idx];
  			s->locked++;
  			set_bit(R5_LOCKED, &dev->flags);
  			set_bit(R5_Wantwrite, &dev->flags);
  		}
  		if (sh->ops.zero_sum_result & SUM_CHECK_Q_RESULT) {
  			dev = &sh->dev[qd_idx];
  			s->locked++;
  			set_bit(R5_LOCKED, &dev->flags);
  			set_bit(R5_Wantwrite, &dev->flags);
  		}
  		if (WARN_ONCE(dev && !test_bit(R5_UPTODATE, &dev->flags),
  			      "%s: disk%td not up to date\n",
  			      mdname(conf->mddev),
  			      dev - (struct r5dev *) &sh->dev)) {
  			clear_bit(R5_LOCKED, &dev->flags);
  			clear_bit(R5_Wantwrite, &dev->flags);
  			s->locked--;
  		}
  		clear_bit(STRIPE_DEGRADED, &sh->state);
  
  		set_bit(STRIPE_INSYNC, &sh->state);
  		break;
  	case check_state_run:
  	case check_state_run_q:
  	case check_state_run_pq:
  		break; /* we will be called again upon completion */
  	case check_state_check_result:
  		sh->check_state = check_state_idle;
  
  		/* handle a successful check operation, if parity is correct
  		 * we are done.  Otherwise update the mismatch count and repair
  		 * parity if !MD_RECOVERY_CHECK
  		 */
  		if (sh->ops.zero_sum_result == 0) {
  			/* both parities are correct */
  			if (!s->failed)
  				set_bit(STRIPE_INSYNC, &sh->state);
  			else {
  				/* in contrast to the raid5 case we can validate
  				 * parity, but still have a failure to write
  				 * back
  				 */
  				sh->check_state = check_state_compute_result;
  				/* Returning at this point means that we may go
  				 * off and bring p and/or q uptodate again so
  				 * we make sure to check zero_sum_result again
  				 * to verify if p or q need writeback
  				 */
  			}
  		} else {
  			atomic64_add(RAID5_STRIPE_SECTORS(conf), &conf->mddev->resync_mismatches);
  			if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery)) {
  				/* don't try to repair!! */
  				set_bit(STRIPE_INSYNC, &sh->state);
  				pr_warn_ratelimited("%s: mismatch sector in range "
  						    "%llu-%llu\n", mdname(conf->mddev),
  						    (unsigned long long) sh->sector,
  						    (unsigned long long) sh->sector +
  						    RAID5_STRIPE_SECTORS(conf));
  			} else {
  				int *target = &sh->ops.target;
  
  				sh->ops.target = -1;
  				sh->ops.target2 = -1;
  				sh->check_state = check_state_compute_run;
  				set_bit(STRIPE_COMPUTE_RUN, &sh->state);
  				set_bit(STRIPE_OP_COMPUTE_BLK, &s->ops_request);
  				if (sh->ops.zero_sum_result & SUM_CHECK_P_RESULT) {
  					set_bit(R5_Wantcompute,
  						&sh->dev[pd_idx].flags);
  					*target = pd_idx;
  					target = &sh->ops.target2;
  					s->uptodate++;
  				}
  				if (sh->ops.zero_sum_result & SUM_CHECK_Q_RESULT) {
  					set_bit(R5_Wantcompute,
  						&sh->dev[qd_idx].flags);
  					*target = qd_idx;
  					s->uptodate++;
  				}
  			}
  		}
  		break;
  	case check_state_compute_run:
  		break;
  	default:
  		pr_warn("%s: unknown check_state: %d sector: %llu\n",
  			__func__, sh->check_state,
  			(unsigned long long) sh->sector);
  		BUG();
  	}
  }
  
  static void handle_stripe_expansion(struct r5conf *conf, struct stripe_head *sh)
  {
  	int i;
  
  	/* We have read all the blocks in this stripe and now we need to
  	 * copy some of them into a target stripe for expand.
  	 */
  	struct dma_async_tx_descriptor *tx = NULL;
  	BUG_ON(sh->batch_head);
  	clear_bit(STRIPE_EXPAND_SOURCE, &sh->state);
  	for (i = 0; i < sh->disks; i++)
  		if (i != sh->pd_idx && i != sh->qd_idx) {
  			int dd_idx, j;
  			struct stripe_head *sh2;
  			struct async_submit_ctl submit;
  
  			sector_t bn = raid5_compute_blocknr(sh, i, 1);
  			sector_t s = raid5_compute_sector(conf, bn, 0,
  							  &dd_idx, NULL);
  			sh2 = raid5_get_active_stripe(conf, s, 0, 1, 1);
  			if (sh2 == NULL)
  				/* so far only the early blocks of this stripe
  				 * have been requested.  When later blocks
  				 * get requested, we will try again
  				 */
  				continue;
  			if (!test_bit(STRIPE_EXPANDING, &sh2->state) ||
  			   test_bit(R5_Expanded, &sh2->dev[dd_idx].flags)) {
  				/* must have already done this block */
  				raid5_release_stripe(sh2);
  				continue;
  			}
  
  			/* place all the copies on one channel */
  			init_async_submit(&submit, 0, tx, NULL, NULL, NULL);
  			tx = async_memcpy(sh2->dev[dd_idx].page,
  					  sh->dev[i].page, sh2->dev[dd_idx].offset,
  					  sh->dev[i].offset, RAID5_STRIPE_SIZE(conf),
  					  &submit);
  
  			set_bit(R5_Expanded, &sh2->dev[dd_idx].flags);
  			set_bit(R5_UPTODATE, &sh2->dev[dd_idx].flags);
  			for (j = 0; j < conf->raid_disks; j++)
  				if (j != sh2->pd_idx &&
  				    j != sh2->qd_idx &&
  				    !test_bit(R5_Expanded, &sh2->dev[j].flags))
  					break;
  			if (j == conf->raid_disks) {
  				set_bit(STRIPE_EXPAND_READY, &sh2->state);
  				set_bit(STRIPE_HANDLE, &sh2->state);
  			}
  			raid5_release_stripe(sh2);
  
  		}
  	/* done submitting copies, wait for them to complete */
  	async_tx_quiesce(&tx);
  }
  
  /*
   * handle_stripe - do things to a stripe.
   *
   * We lock the stripe by setting STRIPE_ACTIVE and then examine the
   * state of various bits to see what needs to be done.
   * Possible results:
   *    return some read requests which now have data
   *    return some write requests which are safely on storage
   *    schedule a read on some buffers
   *    schedule a write of some buffers
   *    return confirmation of parity correctness
   *
   */
  
  static void analyse_stripe(struct stripe_head *sh, struct stripe_head_state *s)
  {
  	struct r5conf *conf = sh->raid_conf;
  	int disks = sh->disks;
  	struct r5dev *dev;
  	int i;
  	int do_recovery = 0;
  
  	memset(s, 0, sizeof(*s));
  
  	s->expanding = test_bit(STRIPE_EXPAND_SOURCE, &sh->state) && !sh->batch_head;
  	s->expanded = test_bit(STRIPE_EXPAND_READY, &sh->state) && !sh->batch_head;
  	s->failed_num[0] = -1;
  	s->failed_num[1] = -1;
  	s->log_failed = r5l_log_disk_error(conf);
  
  	/* Now to look around and see what can be done */
  	rcu_read_lock();
  	for (i=disks; i--; ) {
  		struct md_rdev *rdev;
  		sector_t first_bad;
  		int bad_sectors;
  		int is_bad = 0;
  
  		dev = &sh->dev[i];
  
  		pr_debug("check %d: state 0x%lx read %p write %p written %p\n",
  			 i, dev->flags,
  			 dev->toread, dev->towrite, dev->written);
  		/* maybe we can reply to a read
  		 *
  		 * new wantfill requests are only permitted while
  		 * ops_complete_biofill is guaranteed to be inactive
  		 */
  		if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread &&
  		    !test_bit(STRIPE_BIOFILL_RUN, &sh->state))
  			set_bit(R5_Wantfill, &dev->flags);
  
  		/* now count some things */
  		if (test_bit(R5_LOCKED, &dev->flags))
  			s->locked++;
  		if (test_bit(R5_UPTODATE, &dev->flags))
  			s->uptodate++;
  		if (test_bit(R5_Wantcompute, &dev->flags)) {
  			s->compute++;
  			BUG_ON(s->compute > 2);
  		}
  
  		if (test_bit(R5_Wantfill, &dev->flags))
  			s->to_fill++;
  		else if (dev->toread)
  			s->to_read++;
  		if (dev->towrite) {
  			s->to_write++;
  			if (!test_bit(R5_OVERWRITE, &dev->flags))
  				s->non_overwrite++;
  		}
  		if (dev->written)
  			s->written++;
  		/* Prefer to use the replacement for reads, but only
  		 * if it is recovered enough and has no bad blocks.
  		 */
  		rdev = rcu_dereference(conf->disks[i].replacement);
  		if (rdev && !test_bit(Faulty, &rdev->flags) &&
  		    rdev->recovery_offset >= sh->sector + RAID5_STRIPE_SECTORS(conf) &&
  		    !is_badblock(rdev, sh->sector, RAID5_STRIPE_SECTORS(conf),
  				 &first_bad, &bad_sectors))
  			set_bit(R5_ReadRepl, &dev->flags);
  		else {
  			if (rdev && !test_bit(Faulty, &rdev->flags))
  				set_bit(R5_NeedReplace, &dev->flags);
  			else
  				clear_bit(R5_NeedReplace, &dev->flags);
  			rdev = rcu_dereference(conf->disks[i].rdev);
  			clear_bit(R5_ReadRepl, &dev->flags);
  		}
  		if (rdev && test_bit(Faulty, &rdev->flags))
  			rdev = NULL;
  		if (rdev) {
  			is_bad = is_badblock(rdev, sh->sector, RAID5_STRIPE_SECTORS(conf),
  					     &first_bad, &bad_sectors);
  			if (s->blocked_rdev == NULL
  			    && (test_bit(Blocked, &rdev->flags)
  				|| is_bad < 0)) {
  				if (is_bad < 0)
  					set_bit(BlockedBadBlocks,
  						&rdev->flags);
  				s->blocked_rdev = rdev;
  				atomic_inc(&rdev->nr_pending);
  			}
  		}
  		clear_bit(R5_Insync, &dev->flags);
  		if (!rdev)
  			/* Not in-sync */;
  		else if (is_bad) {
  			/* also not in-sync */
  			if (!test_bit(WriteErrorSeen, &rdev->flags) &&
  			    test_bit(R5_UPTODATE, &dev->flags)) {
  				/* treat as in-sync, but with a read error
  				 * which we can now try to correct
  				 */
  				set_bit(R5_Insync, &dev->flags);
  				set_bit(R5_ReadError, &dev->flags);
  			}
  		} else if (test_bit(In_sync, &rdev->flags))
  			set_bit(R5_Insync, &dev->flags);
  		else if (sh->sector + RAID5_STRIPE_SECTORS(conf) <= rdev->recovery_offset)
  			/* in sync if before recovery_offset */
  			set_bit(R5_Insync, &dev->flags);
  		else if (test_bit(R5_UPTODATE, &dev->flags) &&
  			 test_bit(R5_Expanded, &dev->flags))
  			/* If we've reshaped into here, we assume it is Insync.
  			 * We will shortly update recovery_offset to make
  			 * it official.
  			 */
  			set_bit(R5_Insync, &dev->flags);
  
  		if (test_bit(R5_WriteError, &dev->flags)) {
  			/* This flag does not apply to '.replacement'
  			 * only to .rdev, so make sure to check that*/
  			struct md_rdev *rdev2 = rcu_dereference(
  				conf->disks[i].rdev);
  			if (rdev2 == rdev)
  				clear_bit(R5_Insync, &dev->flags);
  			if (rdev2 && !test_bit(Faulty, &rdev2->flags)) {
  				s->handle_bad_blocks = 1;
  				atomic_inc(&rdev2->nr_pending);
  			} else
  				clear_bit(R5_WriteError, &dev->flags);
  		}
  		if (test_bit(R5_MadeGood, &dev->flags)) {
  			/* This flag does not apply to '.replacement'
  			 * only to .rdev, so make sure to check that*/
  			struct md_rdev *rdev2 = rcu_dereference(
  				conf->disks[i].rdev);
  			if (rdev2 && !test_bit(Faulty, &rdev2->flags)) {
  				s->handle_bad_blocks = 1;
  				atomic_inc(&rdev2->nr_pending);
  			} else
  				clear_bit(R5_MadeGood, &dev->flags);
  		}
  		if (test_bit(R5_MadeGoodRepl, &dev->flags)) {
  			struct md_rdev *rdev2 = rcu_dereference(
  				conf->disks[i].replacement);
  			if (rdev2 && !test_bit(Faulty, &rdev2->flags)) {
  				s->handle_bad_blocks = 1;
  				atomic_inc(&rdev2->nr_pending);
  			} else
  				clear_bit(R5_MadeGoodRepl, &dev->flags);
  		}
  		if (!test_bit(R5_Insync, &dev->flags)) {
  			/* The ReadError flag will just be confusing now */
  			clear_bit(R5_ReadError, &dev->flags);
  			clear_bit(R5_ReWrite, &dev->flags);
  		}
  		if (test_bit(R5_ReadError, &dev->flags))
  			clear_bit(R5_Insync, &dev->flags);
  		if (!test_bit(R5_Insync, &dev->flags)) {
  			if (s->failed < 2)
  				s->failed_num[s->failed] = i;
  			s->failed++;
  			if (rdev && !test_bit(Faulty, &rdev->flags))
  				do_recovery = 1;
  			else if (!rdev) {
  				rdev = rcu_dereference(
  				    conf->disks[i].replacement);
  				if (rdev && !test_bit(Faulty, &rdev->flags))
  					do_recovery = 1;
  			}
  		}
  
  		if (test_bit(R5_InJournal, &dev->flags))
  			s->injournal++;
  		if (test_bit(R5_InJournal, &dev->flags) && dev->written)
  			s->just_cached++;
  	}
  	if (test_bit(STRIPE_SYNCING, &sh->state)) {
  		/* If there is a failed device being replaced,
  		 *     we must be recovering.
  		 * else if we are after recovery_cp, we must be syncing
  		 * else if MD_RECOVERY_REQUESTED is set, we also are syncing.
  		 * else we can only be replacing
  		 * sync and recovery both need to read all devices, and so
  		 * use the same flag.
  		 */
  		if (do_recovery ||
  		    sh->sector >= conf->mddev->recovery_cp ||
  		    test_bit(MD_RECOVERY_REQUESTED, &(conf->mddev->recovery)))
  			s->syncing = 1;
  		else
  			s->replacing = 1;
  	}
  	rcu_read_unlock();
  }
  
  /*
   * Return '1' if this is a member of batch, or '0' if it is a lone stripe or
   * a head which can now be handled.
   */
  static int clear_batch_ready(struct stripe_head *sh)
  {
  	struct stripe_head *tmp;
  	if (!test_and_clear_bit(STRIPE_BATCH_READY, &sh->state))
  		return (sh->batch_head && sh->batch_head != sh);
  	spin_lock(&sh->stripe_lock);
  	if (!sh->batch_head) {
  		spin_unlock(&sh->stripe_lock);
  		return 0;
  	}
  
  	/*
  	 * this stripe could be added to a batch list before we check
  	 * BATCH_READY, skips it
  	 */
  	if (sh->batch_head != sh) {
  		spin_unlock(&sh->stripe_lock);
  		return 1;
  	}
  	spin_lock(&sh->batch_lock);
  	list_for_each_entry(tmp, &sh->batch_list, batch_list)
  		clear_bit(STRIPE_BATCH_READY, &tmp->state);
  	spin_unlock(&sh->batch_lock);
  	spin_unlock(&sh->stripe_lock);
  
  	/*
  	 * BATCH_READY is cleared, no new stripes can be added.
  	 * batch_list can be accessed without lock
  	 */
  	return 0;
  }
  
  static void break_stripe_batch_list(struct stripe_head *head_sh,
  				    unsigned long handle_flags)
  {
  	struct stripe_head *sh, *next;
  	int i;
  	int do_wakeup = 0;
  
  	list_for_each_entry_safe(sh, next, &head_sh->batch_list, batch_list) {
  
  		list_del_init(&sh->batch_list);
  
  		WARN_ONCE(sh->state & ((1 << STRIPE_ACTIVE) |
  					  (1 << STRIPE_SYNCING) |
  					  (1 << STRIPE_REPLACED) |
  					  (1 << STRIPE_DELAYED) |
  					  (1 << STRIPE_BIT_DELAY) |
  					  (1 << STRIPE_FULL_WRITE) |
  					  (1 << STRIPE_BIOFILL_RUN) |
  					  (1 << STRIPE_COMPUTE_RUN)  |
  					  (1 << STRIPE_DISCARD) |
  					  (1 << STRIPE_BATCH_READY) |
  					  (1 << STRIPE_BATCH_ERR) |
  					  (1 << STRIPE_BITMAP_PENDING)),
  			"stripe state: %lx\n", sh->state);
  		WARN_ONCE(head_sh->state & ((1 << STRIPE_DISCARD) |
  					      (1 << STRIPE_REPLACED)),
  			"head stripe state: %lx\n", head_sh->state);
  
  		set_mask_bits(&sh->state, ~(STRIPE_EXPAND_SYNC_FLAGS |
  					    (1 << STRIPE_PREREAD_ACTIVE) |
  					    (1 << STRIPE_DEGRADED) |
  					    (1 << STRIPE_ON_UNPLUG_LIST)),
  			      head_sh->state & (1 << STRIPE_INSYNC));
  
  		sh->check_state = head_sh->check_state;
  		sh->reconstruct_state = head_sh->reconstruct_state;
  		spin_lock_irq(&sh->stripe_lock);
  		sh->batch_head = NULL;
  		spin_unlock_irq(&sh->stripe_lock);
  		for (i = 0; i < sh->disks; i++) {
  			if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
  				do_wakeup = 1;
  			sh->dev[i].flags = head_sh->dev[i].flags &
  				(~((1 << R5_WriteError) | (1 << R5_Overlap)));
  		}
  		if (handle_flags == 0 ||
  		    sh->state & handle_flags)
  			set_bit(STRIPE_HANDLE, &sh->state);
  		raid5_release_stripe(sh);
  	}
  	spin_lock_irq(&head_sh->stripe_lock);
  	head_sh->batch_head = NULL;
  	spin_unlock_irq(&head_sh->stripe_lock);
  	for (i = 0; i < head_sh->disks; i++)
  		if (test_and_clear_bit(R5_Overlap, &head_sh->dev[i].flags))
  			do_wakeup = 1;
  	if (head_sh->state & handle_flags)
  		set_bit(STRIPE_HANDLE, &head_sh->state);
  
  	if (do_wakeup)
  		wake_up(&head_sh->raid_conf->wait_for_overlap);
  }
  
  static void handle_stripe(struct stripe_head *sh)
  {
  	struct stripe_head_state s;
  	struct r5conf *conf = sh->raid_conf;
  	int i;
  	int prexor;
  	int disks = sh->disks;
  	struct r5dev *pdev, *qdev;
  
  	clear_bit(STRIPE_HANDLE, &sh->state);
  
  	/*
  	 * handle_stripe should not continue handle the batched stripe, only
  	 * the head of batch list or lone stripe can continue. Otherwise we
  	 * could see break_stripe_batch_list warns about the STRIPE_ACTIVE
  	 * is set for the batched stripe.
  	 */
  	if (clear_batch_ready(sh))
  		return;
  
  	if (test_and_set_bit_lock(STRIPE_ACTIVE, &sh->state)) {
  		/* already being handled, ensure it gets handled
  		 * again when current action finishes */
  		set_bit(STRIPE_HANDLE, &sh->state);
  		return;
  	}
  
  	if (test_and_clear_bit(STRIPE_BATCH_ERR, &sh->state))
  		break_stripe_batch_list(sh, 0);
  
  	if (test_bit(STRIPE_SYNC_REQUESTED, &sh->state) && !sh->batch_head) {
  		spin_lock(&sh->stripe_lock);
  		/*
  		 * Cannot process 'sync' concurrently with 'discard'.
  		 * Flush data in r5cache before 'sync'.
  		 */
  		if (!test_bit(STRIPE_R5C_PARTIAL_STRIPE, &sh->state) &&
  		    !test_bit(STRIPE_R5C_FULL_STRIPE, &sh->state) &&
  		    !test_bit(STRIPE_DISCARD, &sh->state) &&
  		    test_and_clear_bit(STRIPE_SYNC_REQUESTED, &sh->state)) {
  			set_bit(STRIPE_SYNCING, &sh->state);
  			clear_bit(STRIPE_INSYNC, &sh->state);
  			clear_bit(STRIPE_REPLACED, &sh->state);
  		}
  		spin_unlock(&sh->stripe_lock);
  	}
  	clear_bit(STRIPE_DELAYED, &sh->state);
  
  	pr_debug("handling stripe %llu, state=%#lx cnt=%d, "
  		"pd_idx=%d, qd_idx=%d\n, check:%d, reconstruct:%d\n",
  	       (unsigned long long)sh->sector, sh->state,
  	       atomic_read(&sh->count), sh->pd_idx, sh->qd_idx,
  	       sh->check_state, sh->reconstruct_state);
  
  	analyse_stripe(sh, &s);
  
  	if (test_bit(STRIPE_LOG_TRAPPED, &sh->state))
  		goto finish;
  
  	if (s.handle_bad_blocks ||
  	    test_bit(MD_SB_CHANGE_PENDING, &conf->mddev->sb_flags)) {
  		set_bit(STRIPE_HANDLE, &sh->state);
  		goto finish;
  	}
  
  	if (unlikely(s.blocked_rdev)) {
  		if (s.syncing || s.expanding || s.expanded ||
  		    s.replacing || s.to_write || s.written) {
  			set_bit(STRIPE_HANDLE, &sh->state);
  			goto finish;
  		}
  		/* There is nothing for the blocked_rdev to block */
  		rdev_dec_pending(s.blocked_rdev, conf->mddev);
  		s.blocked_rdev = NULL;
  	}
  
  	if (s.to_fill && !test_bit(STRIPE_BIOFILL_RUN, &sh->state)) {
  		set_bit(STRIPE_OP_BIOFILL, &s.ops_request);
  		set_bit(STRIPE_BIOFILL_RUN, &sh->state);
  	}
  
  	pr_debug("locked=%d uptodate=%d to_read=%d"
  	       " to_write=%d failed=%d failed_num=%d,%d\n",
  	       s.locked, s.uptodate, s.to_read, s.to_write, s.failed,
  	       s.failed_num[0], s.failed_num[1]);
  	/*
  	 * check if the array has lost more than max_degraded devices and,
  	 * if so, some requests might need to be failed.
  	 *
  	 * When journal device failed (log_failed), we will only process
  	 * the stripe if there is data need write to raid disks
  	 */
  	if (s.failed > conf->max_degraded ||
  	    (s.log_failed && s.injournal == 0)) {
  		sh->check_state = 0;
  		sh->reconstruct_state = 0;
  		break_stripe_batch_list(sh, 0);
  		if (s.to_read+s.to_write+s.written)
  			handle_failed_stripe(conf, sh, &s, disks);
  		if (s.syncing + s.replacing)
  			handle_failed_sync(conf, sh, &s);
  	}
  
  	/* Now we check to see if any write operations have recently
  	 * completed
  	 */
  	prexor = 0;
  	if (sh->reconstruct_state == reconstruct_state_prexor_drain_result)
  		prexor = 1;
  	if (sh->reconstruct_state == reconstruct_state_drain_result ||
  	    sh->reconstruct_state == reconstruct_state_prexor_drain_result) {
  		sh->reconstruct_state = reconstruct_state_idle;
  
  		/* All the 'written' buffers and the parity block are ready to
  		 * be written back to disk
  		 */
  		BUG_ON(!test_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags) &&
  		       !test_bit(R5_Discard, &sh->dev[sh->pd_idx].flags));
  		BUG_ON(sh->qd_idx >= 0 &&
  		       !test_bit(R5_UPTODATE, &sh->dev[sh->qd_idx].flags) &&
  		       !test_bit(R5_Discard, &sh->dev[sh->qd_idx].flags));
  		for (i = disks; i--; ) {
  			struct r5dev *dev = &sh->dev[i];
  			if (test_bit(R5_LOCKED, &dev->flags) &&
  				(i == sh->pd_idx || i == sh->qd_idx ||
  				 dev->written || test_bit(R5_InJournal,
  							  &dev->flags))) {
  				pr_debug("Writing block %d\n", i);
  				set_bit(R5_Wantwrite, &dev->flags);
  				if (prexor)
  					continue;
  				if (s.failed > 1)
  					continue;
  				if (!test_bit(R5_Insync, &dev->flags) ||
  				    ((i == sh->pd_idx || i == sh->qd_idx)  &&
  				     s.failed == 0))
  					set_bit(STRIPE_INSYNC, &sh->state);
  			}
  		}
  		if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
  			s.dec_preread_active = 1;
  	}
  
  	/*
  	 * might be able to return some write requests if the parity blocks
  	 * are safe, or on a failed drive
  	 */
  	pdev = &sh->dev[sh->pd_idx];
  	s.p_failed = (s.failed >= 1 && s.failed_num[0] == sh->pd_idx)
  		|| (s.failed >= 2 && s.failed_num[1] == sh->pd_idx);
  	qdev = &sh->dev[sh->qd_idx];
  	s.q_failed = (s.failed >= 1 && s.failed_num[0] == sh->qd_idx)
  		|| (s.failed >= 2 && s.failed_num[1] == sh->qd_idx)
  		|| conf->level < 6;
  
  	if (s.written &&
  	    (s.p_failed || ((test_bit(R5_Insync, &pdev->flags)
  			     && !test_bit(R5_LOCKED, &pdev->flags)
  			     && (test_bit(R5_UPTODATE, &pdev->flags) ||
  				 test_bit(R5_Discard, &pdev->flags))))) &&
  	    (s.q_failed || ((test_bit(R5_Insync, &qdev->flags)
  			     && !test_bit(R5_LOCKED, &qdev->flags)
  			     && (test_bit(R5_UPTODATE, &qdev->flags) ||
  				 test_bit(R5_Discard, &qdev->flags))))))
  		handle_stripe_clean_event(conf, sh, disks);
  
  	if (s.just_cached)
  		r5c_handle_cached_data_endio(conf, sh, disks);
  	log_stripe_write_finished(sh);
  
  	/* Now we might consider reading some blocks, either to check/generate
  	 * parity, or to satisfy requests
  	 * or to load a block that is being partially written.
  	 */
  	if (s.to_read || s.non_overwrite
  	    || (s.to_write && s.failed)
  	    || (s.syncing && (s.uptodate + s.compute < disks))
  	    || s.replacing
  	    || s.expanding)
  		handle_stripe_fill(sh, &s, disks);
  
  	/*
  	 * When the stripe finishes full journal write cycle (write to journal
  	 * and raid disk), this is the clean up procedure so it is ready for
  	 * next operation.
  	 */
  	r5c_finish_stripe_write_out(conf, sh, &s);
  
  	/*
  	 * Now to consider new write requests, cache write back and what else,
  	 * if anything should be read.  We do not handle new writes when:
  	 * 1/ A 'write' operation (copy+xor) is already in flight.
  	 * 2/ A 'check' operation is in flight, as it may clobber the parity
  	 *    block.
  	 * 3/ A r5c cache log write is in flight.
  	 */
  
  	if (!sh->reconstruct_state && !sh->check_state && !sh->log_io) {
  		if (!r5c_is_writeback(conf->log)) {
  			if (s.to_write)
  				handle_stripe_dirtying(conf, sh, &s, disks);
  		} else { /* write back cache */
  			int ret = 0;
  
  			/* First, try handle writes in caching phase */
  			if (s.to_write)
  				ret = r5c_try_caching_write(conf, sh, &s,
  							    disks);
  			/*
  			 * If caching phase failed: ret == -EAGAIN
  			 *    OR
  			 * stripe under reclaim: !caching && injournal
  			 *
  			 * fall back to handle_stripe_dirtying()
  			 */
  			if (ret == -EAGAIN ||
  			    /* stripe under reclaim: !caching && injournal */
  			    (!test_bit(STRIPE_R5C_CACHING, &sh->state) &&
  			     s.injournal > 0)) {
  				ret = handle_stripe_dirtying(conf, sh, &s,
  							     disks);
  				if (ret == -EAGAIN)
  					goto finish;
  			}
  		}
  	}
  
  	/* maybe we need to check and possibly fix the parity for this stripe
  	 * Any reads will already have been scheduled, so we just see if enough
  	 * data is available.  The parity check is held off while parity
  	 * dependent operations are in flight.
  	 */
  	if (sh->check_state ||
  	    (s.syncing && s.locked == 0 &&
  	     !test_bit(STRIPE_COMPUTE_RUN, &sh->state) &&
  	     !test_bit(STRIPE_INSYNC, &sh->state))) {
  		if (conf->level == 6)
  			handle_parity_checks6(conf, sh, &s, disks);
  		else
  			handle_parity_checks5(conf, sh, &s, disks);
  	}
  
  	if ((s.replacing || s.syncing) && s.locked == 0
  	    && !test_bit(STRIPE_COMPUTE_RUN, &sh->state)
  	    && !test_bit(STRIPE_REPLACED, &sh->state)) {
  		/* Write out to replacement devices where possible */
  		for (i = 0; i < conf->raid_disks; i++)
  			if (test_bit(R5_NeedReplace, &sh->dev[i].flags)) {
  				WARN_ON(!test_bit(R5_UPTODATE, &sh->dev[i].flags));
  				set_bit(R5_WantReplace, &sh->dev[i].flags);
  				set_bit(R5_LOCKED, &sh->dev[i].flags);
  				s.locked++;
  			}
  		if (s.replacing)
  			set_bit(STRIPE_INSYNC, &sh->state);
  		set_bit(STRIPE_REPLACED, &sh->state);
  	}
  	if ((s.syncing || s.replacing) && s.locked == 0 &&
  	    !test_bit(STRIPE_COMPUTE_RUN, &sh->state) &&
  	    test_bit(STRIPE_INSYNC, &sh->state)) {
  		md_done_sync(conf->mddev, RAID5_STRIPE_SECTORS(conf), 1);
  		clear_bit(STRIPE_SYNCING, &sh->state);
  		if (test_and_clear_bit(R5_Overlap, &sh->dev[sh->pd_idx].flags))
  			wake_up(&conf->wait_for_overlap);
  	}
  
  	/* If the failed drives are just a ReadError, then we might need
  	 * to progress the repair/check process
  	 */
  	if (s.failed <= conf->max_degraded && !conf->mddev->ro)
  		for (i = 0; i < s.failed; i++) {
  			struct r5dev *dev = &sh->dev[s.failed_num[i]];
  			if (test_bit(R5_ReadError, &dev->flags)
  			    && !test_bit(R5_LOCKED, &dev->flags)
  			    && test_bit(R5_UPTODATE, &dev->flags)
  				) {
  				if (!test_bit(R5_ReWrite, &dev->flags)) {
  					set_bit(R5_Wantwrite, &dev->flags);
  					set_bit(R5_ReWrite, &dev->flags);
  				} else
  					/* let's read it back */
  					set_bit(R5_Wantread, &dev->flags);
  				set_bit(R5_LOCKED, &dev->flags);
  				s.locked++;
  			}
  		}
  
  	/* Finish reconstruct operations initiated by the expansion process */
  	if (sh->reconstruct_state == reconstruct_state_result) {
  		struct stripe_head *sh_src
  			= raid5_get_active_stripe(conf, sh->sector, 1, 1, 1);
  		if (sh_src && test_bit(STRIPE_EXPAND_SOURCE, &sh_src->state)) {
  			/* sh cannot be written until sh_src has been read.
  			 * so arrange for sh to be delayed a little
  			 */
  			set_bit(STRIPE_DELAYED, &sh->state);
  			set_bit(STRIPE_HANDLE, &sh->state);
  			if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE,
  					      &sh_src->state))
  				atomic_inc(&conf->preread_active_stripes);
  			raid5_release_stripe(sh_src);
  			goto finish;
  		}
  		if (sh_src)
  			raid5_release_stripe(sh_src);
  
  		sh->reconstruct_state = reconstruct_state_idle;
  		clear_bit(STRIPE_EXPANDING, &sh->state);
  		for (i = conf->raid_disks; i--; ) {
  			set_bit(R5_Wantwrite, &sh->dev[i].flags);
  			set_bit(R5_LOCKED, &sh->dev[i].flags);
  			s.locked++;
  		}
  	}
  
  	if (s.expanded && test_bit(STRIPE_EXPANDING, &sh->state) &&
  	    !sh->reconstruct_state) {
  		/* Need to write out all blocks after computing parity */
  		sh->disks = conf->raid_disks;
  		stripe_set_idx(sh->sector, conf, 0, sh);
  		schedule_reconstruction(sh, &s, 1, 1);
  	} else if (s.expanded && !sh->reconstruct_state && s.locked == 0) {
  		clear_bit(STRIPE_EXPAND_READY, &sh->state);
  		atomic_dec(&conf->reshape_stripes);
  		wake_up(&conf->wait_for_overlap);
  		md_done_sync(conf->mddev, RAID5_STRIPE_SECTORS(conf), 1);
  	}
  
  	if (s.expanding && s.locked == 0 &&
  	    !test_bit(STRIPE_COMPUTE_RUN, &sh->state))
  		handle_stripe_expansion(conf, sh);
  
  finish:
  	/* wait for this device to become unblocked */
  	if (unlikely(s.blocked_rdev)) {
  		if (conf->mddev->external)
  			md_wait_for_blocked_rdev(s.blocked_rdev,
  						 conf->mddev);
  		else
  			/* Internal metadata will immediately
  			 * be written by raid5d, so we don't
  			 * need to wait here.
  			 */
  			rdev_dec_pending(s.blocked_rdev,
  					 conf->mddev);
  	}
  
  	if (s.handle_bad_blocks)
  		for (i = disks; i--; ) {
  			struct md_rdev *rdev;
  			struct r5dev *dev = &sh->dev[i];
  			if (test_and_clear_bit(R5_WriteError, &dev->flags)) {
  				/* We own a safe reference to the rdev */
  				rdev = conf->disks[i].rdev;
  				if (!rdev_set_badblocks(rdev, sh->sector,
  							RAID5_STRIPE_SECTORS(conf), 0))
  					md_error(conf->mddev, rdev);
  				rdev_dec_pending(rdev, conf->mddev);
  			}
  			if (test_and_clear_bit(R5_MadeGood, &dev->flags)) {
  				rdev = conf->disks[i].rdev;
  				rdev_clear_badblocks(rdev, sh->sector,
  						     RAID5_STRIPE_SECTORS(conf), 0);
  				rdev_dec_pending(rdev, conf->mddev);
  			}
  			if (test_and_clear_bit(R5_MadeGoodRepl, &dev->flags)) {
  				rdev = conf->disks[i].replacement;
  				if (!rdev)
  					/* rdev have been moved down */
  					rdev = conf->disks[i].rdev;
  				rdev_clear_badblocks(rdev, sh->sector,
  						     RAID5_STRIPE_SECTORS(conf), 0);
  				rdev_dec_pending(rdev, conf->mddev);
  			}
  		}
  
  	if (s.ops_request)
  		raid_run_ops(sh, s.ops_request);
  
  	ops_run_io(sh, &s);
  
  	if (s.dec_preread_active) {
  		/* We delay this until after ops_run_io so that if make_request
  		 * is waiting on a flush, it won't continue until the writes
  		 * have actually been submitted.
  		 */
  		atomic_dec(&conf->preread_active_stripes);
  		if (atomic_read(&conf->preread_active_stripes) <
  		    IO_THRESHOLD)
  			md_wakeup_thread(conf->mddev->thread);
  	}
  
  	clear_bit_unlock(STRIPE_ACTIVE, &sh->state);
  }
  
  static void raid5_activate_delayed(struct r5conf *conf)
  {
  	if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD) {
  		while (!list_empty(&conf->delayed_list)) {
  			struct list_head *l = conf->delayed_list.next;
  			struct stripe_head *sh;
  			sh = list_entry(l, struct stripe_head, lru);
  			list_del_init(l);
  			clear_bit(STRIPE_DELAYED, &sh->state);
  			if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
  				atomic_inc(&conf->preread_active_stripes);
  			list_add_tail(&sh->lru, &conf->hold_list);
  			raid5_wakeup_stripe_thread(sh);
  		}
  	}
  }
  
  static void activate_bit_delay(struct r5conf *conf,
  	struct list_head *temp_inactive_list)
  {
  	/* device_lock is held */
  	struct list_head head;
  	list_add(&head, &conf->bitmap_list);
  	list_del_init(&conf->bitmap_list);
  	while (!list_empty(&head)) {
  		struct stripe_head *sh = list_entry(head.next, struct stripe_head, lru);
  		int hash;
  		list_del_init(&sh->lru);
  		atomic_inc(&sh->count);
  		hash = sh->hash_lock_index;
  		__release_stripe(conf, sh, &temp_inactive_list[hash]);
  	}
  }
  
  static int in_chunk_boundary(struct mddev *mddev, struct bio *bio)
  {
  	struct r5conf *conf = mddev->private;
  	sector_t sector = bio->bi_iter.bi_sector;
  	unsigned int chunk_sectors;
  	unsigned int bio_sectors = bio_sectors(bio);
  
  	WARN_ON_ONCE(bio->bi_partno);
  
  	chunk_sectors = min(conf->chunk_sectors, conf->prev_chunk_sectors);
  	return  chunk_sectors >=
  		((sector & (chunk_sectors - 1)) + bio_sectors);
  }
  
  /*
   *  add bio to the retry LIFO  ( in O(1) ... we are in interrupt )
   *  later sampled by raid5d.
   */
  static void add_bio_to_retry(struct bio *bi,struct r5conf *conf)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&conf->device_lock, flags);
  
  	bi->bi_next = conf->retry_read_aligned_list;
  	conf->retry_read_aligned_list = bi;
  
  	spin_unlock_irqrestore(&conf->device_lock, flags);
  	md_wakeup_thread(conf->mddev->thread);
  }
  
  static struct bio *remove_bio_from_retry(struct r5conf *conf,
  					 unsigned int *offset)
  {
  	struct bio *bi;
  
  	bi = conf->retry_read_aligned;
  	if (bi) {
  		*offset = conf->retry_read_offset;
  		conf->retry_read_aligned = NULL;
  		return bi;
  	}
  	bi = conf->retry_read_aligned_list;
  	if(bi) {
  		conf->retry_read_aligned_list = bi->bi_next;
  		bi->bi_next = NULL;
  		*offset = 0;
  	}
  
  	return bi;
  }
  
  /*
   *  The "raid5_align_endio" should check if the read succeeded and if it
   *  did, call bio_endio on the original bio (having bio_put the new bio
   *  first).
   *  If the read failed..
   */
  static void raid5_align_endio(struct bio *bi)
  {
  	struct bio* raid_bi  = bi->bi_private;
  	struct mddev *mddev;
  	struct r5conf *conf;
  	struct md_rdev *rdev;
  	blk_status_t error = bi->bi_status;
  
  	bio_put(bi);
  
  	rdev = (void*)raid_bi->bi_next;
  	raid_bi->bi_next = NULL;
  	mddev = rdev->mddev;
  	conf = mddev->private;
  
  	rdev_dec_pending(rdev, conf->mddev);
  
  	if (!error) {
  		bio_endio(raid_bi);
  		if (atomic_dec_and_test(&conf->active_aligned_reads))
  			wake_up(&conf->wait_for_quiescent);
  		return;
  	}
  
  	pr_debug("raid5_align_endio : io error...handing IO for a retry\n");
  
  	add_bio_to_retry(raid_bi, conf);
  }
  
  static int raid5_read_one_chunk(struct mddev *mddev, struct bio *raid_bio)
  {
  	struct r5conf *conf = mddev->private;
  	int dd_idx;
  	struct bio* align_bi;
  	struct md_rdev *rdev;
  	sector_t end_sector;
  
  	if (!in_chunk_boundary(mddev, raid_bio)) {
  		pr_debug("%s: non aligned\n", __func__);
  		return 0;
  	}
  	/*
  	 * use bio_clone_fast to make a copy of the bio
  	 */
  	align_bi = bio_clone_fast(raid_bio, GFP_NOIO, &mddev->bio_set);
  	if (!align_bi)
  		return 0;
  	/*
  	 *   set bi_end_io to a new function, and set bi_private to the
  	 *     original bio.
  	 */
  	align_bi->bi_end_io  = raid5_align_endio;
  	align_bi->bi_private = raid_bio;
  	/*
  	 *	compute position
  	 */
  	align_bi->bi_iter.bi_sector =
  		raid5_compute_sector(conf, raid_bio->bi_iter.bi_sector,
  				     0, &dd_idx, NULL);
  
  	end_sector = bio_end_sector(align_bi);
  	rcu_read_lock();
  	rdev = rcu_dereference(conf->disks[dd_idx].replacement);
  	if (!rdev || test_bit(Faulty, &rdev->flags) ||
  	    rdev->recovery_offset < end_sector) {
  		rdev = rcu_dereference(conf->disks[dd_idx].rdev);
  		if (rdev &&
  		    (test_bit(Faulty, &rdev->flags) ||
  		    !(test_bit(In_sync, &rdev->flags) ||
  		      rdev->recovery_offset >= end_sector)))
  			rdev = NULL;
  	}
  
  	if (r5c_big_stripe_cached(conf, align_bi->bi_iter.bi_sector)) {
  		rcu_read_unlock();
  		bio_put(align_bi);
  		return 0;
  	}
  
  	if (rdev) {
  		sector_t first_bad;
  		int bad_sectors;
  
  		atomic_inc(&rdev->nr_pending);
  		rcu_read_unlock();
  		raid_bio->bi_next = (void*)rdev;
  		bio_set_dev(align_bi, rdev->bdev);
  
  		if (is_badblock(rdev, align_bi->bi_iter.bi_sector,
  				bio_sectors(align_bi),
  				&first_bad, &bad_sectors)) {
  			bio_put(align_bi);
  			rdev_dec_pending(rdev, mddev);
  			return 0;
  		}
  
  		/* No reshape active, so we can trust rdev->data_offset */
  		align_bi->bi_iter.bi_sector += rdev->data_offset;
  
  		spin_lock_irq(&conf->device_lock);
  		wait_event_lock_irq(conf->wait_for_quiescent,
  				    conf->quiesce == 0,
  				    conf->device_lock);
  		atomic_inc(&conf->active_aligned_reads);
  		spin_unlock_irq(&conf->device_lock);
  
  		if (mddev->gendisk)
  			trace_block_bio_remap(align_bi->bi_disk->queue,
  					      align_bi, disk_devt(mddev->gendisk),
  					      raid_bio->bi_iter.bi_sector);
  		submit_bio_noacct(align_bi);
  		return 1;
  	} else {
  		rcu_read_unlock();
  		bio_put(align_bi);
  		return 0;
  	}
  }
  
  static struct bio *chunk_aligned_read(struct mddev *mddev, struct bio *raid_bio)
  {
  	struct bio *split;
  	sector_t sector = raid_bio->bi_iter.bi_sector;
  	unsigned chunk_sects = mddev->chunk_sectors;
  	unsigned sectors = chunk_sects - (sector & (chunk_sects-1));
  
  	if (sectors < bio_sectors(raid_bio)) {
  		struct r5conf *conf = mddev->private;
  		split = bio_split(raid_bio, sectors, GFP_NOIO, &conf->bio_split);
  		bio_chain(split, raid_bio);
  		submit_bio_noacct(raid_bio);
  		raid_bio = split;
  	}
  
  	if (!raid5_read_one_chunk(mddev, raid_bio))
  		return raid_bio;
  
  	return NULL;
  }
  
  /* __get_priority_stripe - get the next stripe to process
   *
   * Full stripe writes are allowed to pass preread active stripes up until
   * the bypass_threshold is exceeded.  In general the bypass_count
   * increments when the handle_list is handled before the hold_list; however, it
   * will not be incremented when STRIPE_IO_STARTED is sampled set signifying a
   * stripe with in flight i/o.  The bypass_count will be reset when the
   * head of the hold_list has changed, i.e. the head was promoted to the
   * handle_list.
   */
  static struct stripe_head *__get_priority_stripe(struct r5conf *conf, int group)
  {
  	struct stripe_head *sh, *tmp;
  	struct list_head *handle_list = NULL;
  	struct r5worker_group *wg;
  	bool second_try = !r5c_is_writeback(conf->log) &&
  		!r5l_log_disk_error(conf);
  	bool try_loprio = test_bit(R5C_LOG_TIGHT, &conf->cache_state) ||
  		r5l_log_disk_error(conf);
  
  again:
  	wg = NULL;
  	sh = NULL;
  	if (conf->worker_cnt_per_group == 0) {
  		handle_list = try_loprio ? &conf->loprio_list :
  					&conf->handle_list;
  	} else if (group != ANY_GROUP) {
  		handle_list = try_loprio ? &conf->worker_groups[group].loprio_list :
  				&conf->worker_groups[group].handle_list;
  		wg = &conf->worker_groups[group];
  	} else {
  		int i;
  		for (i = 0; i < conf->group_cnt; i++) {
  			handle_list = try_loprio ? &conf->worker_groups[i].loprio_list :
  				&conf->worker_groups[i].handle_list;
  			wg = &conf->worker_groups[i];
  			if (!list_empty(handle_list))
  				break;
  		}
  	}
  
  	pr_debug("%s: handle: %s hold: %s full_writes: %d bypass_count: %d\n",
  		  __func__,
  		  list_empty(handle_list) ? "empty" : "busy",
  		  list_empty(&conf->hold_list) ? "empty" : "busy",
  		  atomic_read(&conf->pending_full_writes), conf->bypass_count);
  
  	if (!list_empty(handle_list)) {
  		sh = list_entry(handle_list->next, typeof(*sh), lru);
  
  		if (list_empty(&conf->hold_list))
  			conf->bypass_count = 0;
  		else if (!test_bit(STRIPE_IO_STARTED, &sh->state)) {
  			if (conf->hold_list.next == conf->last_hold)
  				conf->bypass_count++;
  			else {
  				conf->last_hold = conf->hold_list.next;
  				conf->bypass_count -= conf->bypass_threshold;
  				if (conf->bypass_count < 0)
  					conf->bypass_count = 0;
  			}
  		}
  	} else if (!list_empty(&conf->hold_list) &&
  		   ((conf->bypass_threshold &&
  		     conf->bypass_count > conf->bypass_threshold) ||
  		    atomic_read(&conf->pending_full_writes) == 0)) {
  
  		list_for_each_entry(tmp, &conf->hold_list,  lru) {
  			if (conf->worker_cnt_per_group == 0 ||
  			    group == ANY_GROUP ||
  			    !cpu_online(tmp->cpu) ||
  			    cpu_to_group(tmp->cpu) == group) {
  				sh = tmp;
  				break;
  			}
  		}
  
  		if (sh) {
  			conf->bypass_count -= conf->bypass_threshold;
  			if (conf->bypass_count < 0)
  				conf->bypass_count = 0;
  		}
  		wg = NULL;
  	}
  
  	if (!sh) {
  		if (second_try)
  			return NULL;
  		second_try = true;
  		try_loprio = !try_loprio;
  		goto again;
  	}
  
  	if (wg) {
  		wg->stripes_cnt--;
  		sh->group = NULL;
  	}
  	list_del_init(&sh->lru);
  	BUG_ON(atomic_inc_return(&sh->count) != 1);
  	return sh;
  }
  
  struct raid5_plug_cb {
  	struct blk_plug_cb	cb;
  	struct list_head	list;
  	struct list_head	temp_inactive_list[NR_STRIPE_HASH_LOCKS];
  };
  
  static void raid5_unplug(struct blk_plug_cb *blk_cb, bool from_schedule)
  {
  	struct raid5_plug_cb *cb = container_of(
  		blk_cb, struct raid5_plug_cb, cb);
  	struct stripe_head *sh;
  	struct mddev *mddev = cb->cb.data;
  	struct r5conf *conf = mddev->private;
  	int cnt = 0;
  	int hash;
  
  	if (cb->list.next && !list_empty(&cb->list)) {
  		spin_lock_irq(&conf->device_lock);
  		while (!list_empty(&cb->list)) {
  			sh = list_first_entry(&cb->list, struct stripe_head, lru);
  			list_del_init(&sh->lru);
  			/*
  			 * avoid race release_stripe_plug() sees
  			 * STRIPE_ON_UNPLUG_LIST clear but the stripe
  			 * is still in our list
  			 */
  			smp_mb__before_atomic();
  			clear_bit(STRIPE_ON_UNPLUG_LIST, &sh->state);
  			/*
  			 * STRIPE_ON_RELEASE_LIST could be set here. In that
  			 * case, the count is always > 1 here
  			 */
  			hash = sh->hash_lock_index;
  			__release_stripe(conf, sh, &cb->temp_inactive_list[hash]);
  			cnt++;
  		}
  		spin_unlock_irq(&conf->device_lock);
  	}
  	release_inactive_stripe_list(conf, cb->temp_inactive_list,
  				     NR_STRIPE_HASH_LOCKS);
  	if (mddev->queue)
  		trace_block_unplug(mddev->queue, cnt, !from_schedule);
  	kfree(cb);
  }
  
  static void release_stripe_plug(struct mddev *mddev,
  				struct stripe_head *sh)
  {
  	struct blk_plug_cb *blk_cb = blk_check_plugged(
  		raid5_unplug, mddev,
  		sizeof(struct raid5_plug_cb));
  	struct raid5_plug_cb *cb;
  
  	if (!blk_cb) {
  		raid5_release_stripe(sh);
  		return;
  	}
  
  	cb = container_of(blk_cb, struct raid5_plug_cb, cb);
  
  	if (cb->list.next == NULL) {
  		int i;
  		INIT_LIST_HEAD(&cb->list);
  		for (i = 0; i < NR_STRIPE_HASH_LOCKS; i++)
  			INIT_LIST_HEAD(cb->temp_inactive_list + i);
  	}
  
  	if (!test_and_set_bit(STRIPE_ON_UNPLUG_LIST, &sh->state))
  		list_add_tail(&sh->lru, &cb->list);
  	else
  		raid5_release_stripe(sh);
  }
  
  static void make_discard_request(struct mddev *mddev, struct bio *bi)
  {
  	struct r5conf *conf = mddev->private;
  	sector_t logical_sector, last_sector;
  	struct stripe_head *sh;
  	int stripe_sectors;
  
  	if (mddev->reshape_position != MaxSector)
  		/* Skip discard while reshape is happening */
  		return;
  
  	logical_sector = bi->bi_iter.bi_sector & ~((sector_t)RAID5_STRIPE_SECTORS(conf)-1);
  	last_sector = bio_end_sector(bi);
  
  	bi->bi_next = NULL;
  
  	stripe_sectors = conf->chunk_sectors *
  		(conf->raid_disks - conf->max_degraded);
  	logical_sector = DIV_ROUND_UP_SECTOR_T(logical_sector,
  					       stripe_sectors);
  	sector_div(last_sector, stripe_sectors);
  
  	logical_sector *= conf->chunk_sectors;
  	last_sector *= conf->chunk_sectors;
  
  	for (; logical_sector < last_sector;
  	     logical_sector += RAID5_STRIPE_SECTORS(conf)) {
  		DEFINE_WAIT(w);
  		int d;
  	again:
  		sh = raid5_get_active_stripe(conf, logical_sector, 0, 0, 0);
  		prepare_to_wait(&conf->wait_for_overlap, &w,
  				TASK_UNINTERRUPTIBLE);
  		set_bit(R5_Overlap, &sh->dev[sh->pd_idx].flags);
  		if (test_bit(STRIPE_SYNCING, &sh->state)) {
  			raid5_release_stripe(sh);
  			schedule();
  			goto again;
  		}
  		clear_bit(R5_Overlap, &sh->dev[sh->pd_idx].flags);
  		spin_lock_irq(&sh->stripe_lock);
  		for (d = 0; d < conf->raid_disks; d++) {
  			if (d == sh->pd_idx || d == sh->qd_idx)
  				continue;
  			if (sh->dev[d].towrite || sh->dev[d].toread) {
  				set_bit(R5_Overlap, &sh->dev[d].flags);
  				spin_unlock_irq(&sh->stripe_lock);
  				raid5_release_stripe(sh);
  				schedule();
  				goto again;
  			}
  		}
  		set_bit(STRIPE_DISCARD, &sh->state);
  		finish_wait(&conf->wait_for_overlap, &w);
  		sh->overwrite_disks = 0;
  		for (d = 0; d < conf->raid_disks; d++) {
  			if (d == sh->pd_idx || d == sh->qd_idx)
  				continue;
  			sh->dev[d].towrite = bi;
  			set_bit(R5_OVERWRITE, &sh->dev[d].flags);
  			bio_inc_remaining(bi);
  			md_write_inc(mddev, bi);
  			sh->overwrite_disks++;
  		}
  		spin_unlock_irq(&sh->stripe_lock);
  		if (conf->mddev->bitmap) {
  			for (d = 0;
  			     d < conf->raid_disks - conf->max_degraded;
  			     d++)
  				md_bitmap_startwrite(mddev->bitmap,
  						     sh->sector,
  						     RAID5_STRIPE_SECTORS(conf),
  						     0);
  			sh->bm_seq = conf->seq_flush + 1;
  			set_bit(STRIPE_BIT_DELAY, &sh->state);
  		}
  
  		set_bit(STRIPE_HANDLE, &sh->state);
  		clear_bit(STRIPE_DELAYED, &sh->state);
  		if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
  			atomic_inc(&conf->preread_active_stripes);
  		release_stripe_plug(mddev, sh);
  	}
  
  	bio_endio(bi);
  }
  
  static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
  {
  	struct r5conf *conf = mddev->private;
  	int dd_idx;
  	sector_t new_sector;
  	sector_t logical_sector, last_sector;
  	struct stripe_head *sh;
  	const int rw = bio_data_dir(bi);
  	DEFINE_WAIT(w);
  	bool do_prepare;
  	bool do_flush = false;
  
  	if (unlikely(bi->bi_opf & REQ_PREFLUSH)) {
  		int ret = log_handle_flush_request(conf, bi);
  
  		if (ret == 0)
  			return true;
  		if (ret == -ENODEV) {
  			if (md_flush_request(mddev, bi))
  				return true;
  		}
  		/* ret == -EAGAIN, fallback */
  		/*
  		 * if r5l_handle_flush_request() didn't clear REQ_PREFLUSH,
  		 * we need to flush journal device
  		 */
  		do_flush = bi->bi_opf & REQ_PREFLUSH;
  	}
  
  	if (!md_write_start(mddev, bi))
  		return false;
  	/*
  	 * If array is degraded, better not do chunk aligned read because
  	 * later we might have to read it again in order to reconstruct
  	 * data on failed drives.
  	 */
  	if (rw == READ && mddev->degraded == 0 &&
  	    mddev->reshape_position == MaxSector) {
  		bi = chunk_aligned_read(mddev, bi);
  		if (!bi)
  			return true;
  	}
  
  	if (unlikely(bio_op(bi) == REQ_OP_DISCARD)) {
  		make_discard_request(mddev, bi);
  		md_write_end(mddev);
  		return true;
  	}
  
  	logical_sector = bi->bi_iter.bi_sector & ~((sector_t)RAID5_STRIPE_SECTORS(conf)-1);
  	last_sector = bio_end_sector(bi);
  	bi->bi_next = NULL;
  
  	prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE);
  	for (; logical_sector < last_sector; logical_sector += RAID5_STRIPE_SECTORS(conf)) {
  		int previous;
  		int seq;
  
  		do_prepare = false;
  	retry:
  		seq = read_seqcount_begin(&conf->gen_lock);
  		previous = 0;
  		if (do_prepare)
  			prepare_to_wait(&conf->wait_for_overlap, &w,
  				TASK_UNINTERRUPTIBLE);
  		if (unlikely(conf->reshape_progress != MaxSector)) {
  			/* spinlock is needed as reshape_progress may be
  			 * 64bit on a 32bit platform, and so it might be
  			 * possible to see a half-updated value
  			 * Of course reshape_progress could change after
  			 * the lock is dropped, so once we get a reference
  			 * to the stripe that we think it is, we will have
  			 * to check again.
  			 */
  			spin_lock_irq(&conf->device_lock);
  			if (mddev->reshape_backwards
  			    ? logical_sector < conf->reshape_progress
  			    : logical_sector >= conf->reshape_progress) {
  				previous = 1;
  			} else {
  				if (mddev->reshape_backwards
  				    ? logical_sector < conf->reshape_safe
  				    : logical_sector >= conf->reshape_safe) {
  					spin_unlock_irq(&conf->device_lock);
  					schedule();
  					do_prepare = true;
  					goto retry;
  				}
  			}
  			spin_unlock_irq(&conf->device_lock);
  		}
  
  		new_sector = raid5_compute_sector(conf, logical_sector,
  						  previous,
  						  &dd_idx, NULL);
  		pr_debug("raid456: raid5_make_request, sector %llu logical %llu\n",
  			(unsigned long long)new_sector,
  			(unsigned long long)logical_sector);
  
  		sh = raid5_get_active_stripe(conf, new_sector, previous,
  				       (bi->bi_opf & REQ_RAHEAD), 0);
  		if (sh) {
  			if (unlikely(previous)) {
  				/* expansion might have moved on while waiting for a
  				 * stripe, so we must do the range check again.
  				 * Expansion could still move past after this
  				 * test, but as we are holding a reference to
  				 * 'sh', we know that if that happens,
  				 *  STRIPE_EXPANDING will get set and the expansion
  				 * won't proceed until we finish with the stripe.
  				 */
  				int must_retry = 0;
  				spin_lock_irq(&conf->device_lock);
  				if (mddev->reshape_backwards
  				    ? logical_sector >= conf->reshape_progress
  				    : logical_sector < conf->reshape_progress)
  					/* mismatch, need to try again */
  					must_retry = 1;
  				spin_unlock_irq(&conf->device_lock);
  				if (must_retry) {
  					raid5_release_stripe(sh);
  					schedule();
  					do_prepare = true;
  					goto retry;
  				}
  			}
  			if (read_seqcount_retry(&conf->gen_lock, seq)) {
  				/* Might have got the wrong stripe_head
  				 * by accident
  				 */
  				raid5_release_stripe(sh);
  				goto retry;
  			}
  
  			if (test_bit(STRIPE_EXPANDING, &sh->state) ||
  			    !add_stripe_bio(sh, bi, dd_idx, rw, previous)) {
  				/* Stripe is busy expanding or
  				 * add failed due to overlap.  Flush everything
  				 * and wait a while
  				 */
  				md_wakeup_thread(mddev->thread);
  				raid5_release_stripe(sh);
  				schedule();
  				do_prepare = true;
  				goto retry;
  			}
  			if (do_flush) {
  				set_bit(STRIPE_R5C_PREFLUSH, &sh->state);
  				/* we only need flush for one stripe */
  				do_flush = false;
  			}
  
  			set_bit(STRIPE_HANDLE, &sh->state);
  			clear_bit(STRIPE_DELAYED, &sh->state);
  			if ((!sh->batch_head || sh == sh->batch_head) &&
  			    (bi->bi_opf & REQ_SYNC) &&
  			    !test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
  				atomic_inc(&conf->preread_active_stripes);
  			release_stripe_plug(mddev, sh);
  		} else {
  			/* cannot get stripe for read-ahead, just give-up */
  			bi->bi_status = BLK_STS_IOERR;
  			break;
  		}
  	}
  	finish_wait(&conf->wait_for_overlap, &w);
  
  	if (rw == WRITE)
  		md_write_end(mddev);
  	bio_endio(bi);
  	return true;
  }
  
  static sector_t raid5_size(struct mddev *mddev, sector_t sectors, int raid_disks);
  
  static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, int *skipped)
  {
  	/* reshaping is quite different to recovery/resync so it is
  	 * handled quite separately ... here.
  	 *
  	 * On each call to sync_request, we gather one chunk worth of
  	 * destination stripes and flag them as expanding.
  	 * Then we find all the source stripes and request reads.
  	 * As the reads complete, handle_stripe will copy the data
  	 * into the destination stripe and release that stripe.
  	 */
  	struct r5conf *conf = mddev->private;
  	struct stripe_head *sh;
  	struct md_rdev *rdev;
  	sector_t first_sector, last_sector;
  	int raid_disks = conf->previous_raid_disks;
  	int data_disks = raid_disks - conf->max_degraded;
  	int new_data_disks = conf->raid_disks - conf->max_degraded;
  	int i;
  	int dd_idx;
  	sector_t writepos, readpos, safepos;
  	sector_t stripe_addr;
  	int reshape_sectors;
  	struct list_head stripes;
  	sector_t retn;
  
  	if (sector_nr == 0) {
  		/* If restarting in the middle, skip the initial sectors */
  		if (mddev->reshape_backwards &&
  		    conf->reshape_progress < raid5_size(mddev, 0, 0)) {
  			sector_nr = raid5_size(mddev, 0, 0)
  				- conf->reshape_progress;
  		} else if (mddev->reshape_backwards &&
  			   conf->reshape_progress == MaxSector) {
  			/* shouldn't happen, but just in case, finish up.*/
  			sector_nr = MaxSector;
  		} else if (!mddev->reshape_backwards &&
  			   conf->reshape_progress > 0)
  			sector_nr = conf->reshape_progress;
  		sector_div(sector_nr, new_data_disks);
  		if (sector_nr) {
  			mddev->curr_resync_completed = sector_nr;
  			sysfs_notify_dirent_safe(mddev->sysfs_completed);
  			*skipped = 1;
  			retn = sector_nr;
  			goto finish;
  		}
  	}
  
  	/* We need to process a full chunk at a time.
  	 * If old and new chunk sizes differ, we need to process the
  	 * largest of these
  	 */
  
  	reshape_sectors = max(conf->chunk_sectors, conf->prev_chunk_sectors);
  
  	/* We update the metadata at least every 10 seconds, or when
  	 * the data about to be copied would over-write the source of
  	 * the data at the front of the range.  i.e. one new_stripe
  	 * along from reshape_progress new_maps to after where
  	 * reshape_safe old_maps to
  	 */
  	writepos = conf->reshape_progress;
  	sector_div(writepos, new_data_disks);
  	readpos = conf->reshape_progress;
  	sector_div(readpos, data_disks);
  	safepos = conf->reshape_safe;
  	sector_div(safepos, data_disks);
  	if (mddev->reshape_backwards) {
  		BUG_ON(writepos < reshape_sectors);
  		writepos -= reshape_sectors;
  		readpos += reshape_sectors;
  		safepos += reshape_sectors;
  	} else {
  		writepos += reshape_sectors;
  		/* readpos and safepos are worst-case calculations.
  		 * A negative number is overly pessimistic, and causes
  		 * obvious problems for unsigned storage.  So clip to 0.
  		 */
  		readpos -= min_t(sector_t, reshape_sectors, readpos);
  		safepos -= min_t(sector_t, reshape_sectors, safepos);
  	}
  
  	/* Having calculated the 'writepos' possibly use it
  	 * to set 'stripe_addr' which is where we will write to.
  	 */
  	if (mddev->reshape_backwards) {
  		BUG_ON(conf->reshape_progress == 0);
  		stripe_addr = writepos;
  		BUG_ON((mddev->dev_sectors &
  			~((sector_t)reshape_sectors - 1))
  		       - reshape_sectors - stripe_addr
  		       != sector_nr);
  	} else {
  		BUG_ON(writepos != sector_nr + reshape_sectors);
  		stripe_addr = sector_nr;
  	}
  
  	/* 'writepos' is the most advanced device address we might write.
  	 * 'readpos' is the least advanced device address we might read.
  	 * 'safepos' is the least address recorded in the metadata as having
  	 *     been reshaped.
  	 * If there is a min_offset_diff, these are adjusted either by
  	 * increasing the safepos/readpos if diff is negative, or
  	 * increasing writepos if diff is positive.
  	 * If 'readpos' is then behind 'writepos', there is no way that we can
  	 * ensure safety in the face of a crash - that must be done by userspace
  	 * making a backup of the data.  So in that case there is no particular
  	 * rush to update metadata.
  	 * Otherwise if 'safepos' is behind 'writepos', then we really need to
  	 * update the metadata to advance 'safepos' to match 'readpos' so that
  	 * we can be safe in the event of a crash.
  	 * So we insist on updating metadata if safepos is behind writepos and
  	 * readpos is beyond writepos.
  	 * In any case, update the metadata every 10 seconds.
  	 * Maybe that number should be configurable, but I'm not sure it is
  	 * worth it.... maybe it could be a multiple of safemode_delay???
  	 */
  	if (conf->min_offset_diff < 0) {
  		safepos += -conf->min_offset_diff;
  		readpos += -conf->min_offset_diff;
  	} else
  		writepos += conf->min_offset_diff;
  
  	if ((mddev->reshape_backwards
  	     ? (safepos > writepos && readpos < writepos)
  	     : (safepos < writepos && readpos > writepos)) ||
  	    time_after(jiffies, conf->reshape_checkpoint + 10*HZ)) {
  		/* Cannot proceed until we've updated the superblock... */
  		wait_event(conf->wait_for_overlap,
  			   atomic_read(&conf->reshape_stripes)==0
  			   || test_bit(MD_RECOVERY_INTR, &mddev->recovery));
  		if (atomic_read(&conf->reshape_stripes) != 0)
  			return 0;
  		mddev->reshape_position = conf->reshape_progress;
  		mddev->curr_resync_completed = sector_nr;
  		if (!mddev->reshape_backwards)
  			/* Can update recovery_offset */
  			rdev_for_each(rdev, mddev)
  				if (rdev->raid_disk >= 0 &&
  				    !test_bit(Journal, &rdev->flags) &&
  				    !test_bit(In_sync, &rdev->flags) &&
  				    rdev->recovery_offset < sector_nr)
  					rdev->recovery_offset = sector_nr;
  
  		conf->reshape_checkpoint = jiffies;
  		set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
  		md_wakeup_thread(mddev->thread);
  		wait_event(mddev->sb_wait, mddev->sb_flags == 0 ||
  			   test_bit(MD_RECOVERY_INTR, &mddev->recovery));
  		if (test_bit(MD_RECOVERY_INTR, &mddev->recovery))
  			return 0;
  		spin_lock_irq(&conf->device_lock);
  		conf->reshape_safe = mddev->reshape_position;
  		spin_unlock_irq(&conf->device_lock);
  		wake_up(&conf->wait_for_overlap);
  		sysfs_notify_dirent_safe(mddev->sysfs_completed);
  	}
  
  	INIT_LIST_HEAD(&stripes);
  	for (i = 0; i < reshape_sectors; i += RAID5_STRIPE_SECTORS(conf)) {
  		int j;
  		int skipped_disk = 0;
  		sh = raid5_get_active_stripe(conf, stripe_addr+i, 0, 0, 1);
  		set_bit(STRIPE_EXPANDING, &sh->state);
  		atomic_inc(&conf->reshape_stripes);
  		/* If any of this stripe is beyond the end of the old
  		 * array, then we need to zero those blocks
  		 */
  		for (j=sh->disks; j--;) {
  			sector_t s;
  			if (j == sh->pd_idx)
  				continue;
  			if (conf->level == 6 &&
  			    j == sh->qd_idx)
  				continue;
  			s = raid5_compute_blocknr(sh, j, 0);
  			if (s < raid5_size(mddev, 0, 0)) {
  				skipped_disk = 1;
  				continue;
  			}
  			memset(page_address(sh->dev[j].page), 0, RAID5_STRIPE_SIZE(conf));
  			set_bit(R5_Expanded, &sh->dev[j].flags);
  			set_bit(R5_UPTODATE, &sh->dev[j].flags);
  		}
  		if (!skipped_disk) {
  			set_bit(STRIPE_EXPAND_READY, &sh->state);
  			set_bit(STRIPE_HANDLE, &sh->state);
  		}
  		list_add(&sh->lru, &stripes);
  	}
  	spin_lock_irq(&conf->device_lock);
  	if (mddev->reshape_backwards)
  		conf->reshape_progress -= reshape_sectors * new_data_disks;
  	else
  		conf->reshape_progress += reshape_sectors * new_data_disks;
  	spin_unlock_irq(&conf->device_lock);
  	/* Ok, those stripe are ready. We can start scheduling
  	 * reads on the source stripes.
  	 * The source stripes are determined by mapping the first and last
  	 * block on the destination stripes.
  	 */
  	first_sector =
  		raid5_compute_sector(conf, stripe_addr*(new_data_disks),
  				     1, &dd_idx, NULL);
  	last_sector =
  		raid5_compute_sector(conf, ((stripe_addr+reshape_sectors)
  					    * new_data_disks - 1),
  				     1, &dd_idx, NULL);
  	if (last_sector >= mddev->dev_sectors)
  		last_sector = mddev->dev_sectors - 1;
  	while (first_sector <= last_sector) {
  		sh = raid5_get_active_stripe(conf, first_sector, 1, 0, 1);
  		set_bit(STRIPE_EXPAND_SOURCE, &sh->state);
  		set_bit(STRIPE_HANDLE, &sh->state);
  		raid5_release_stripe(sh);
  		first_sector += RAID5_STRIPE_SECTORS(conf);
  	}
  	/* Now that the sources are clearly marked, we can release
  	 * the destination stripes
  	 */
  	while (!list_empty(&stripes)) {
  		sh = list_entry(stripes.next, struct stripe_head, lru);
  		list_del_init(&sh->lru);
  		raid5_release_stripe(sh);
  	}
  	/* If this takes us to the resync_max point where we have to pause,
  	 * then we need to write out the superblock.
  	 */
  	sector_nr += reshape_sectors;
  	retn = reshape_sectors;
  finish:
  	if (mddev->curr_resync_completed > mddev->resync_max ||
  	    (sector_nr - mddev->curr_resync_completed) * 2
  	    >= mddev->resync_max - mddev->curr_resync_completed) {
  		/* Cannot proceed until we've updated the superblock... */
  		wait_event(conf->wait_for_overlap,
  			   atomic_read(&conf->reshape_stripes) == 0
  			   || test_bit(MD_RECOVERY_INTR, &mddev->recovery));
  		if (atomic_read(&conf->reshape_stripes) != 0)
  			goto ret;
  		mddev->reshape_position = conf->reshape_progress;
  		mddev->curr_resync_completed = sector_nr;
  		if (!mddev->reshape_backwards)
  			/* Can update recovery_offset */
  			rdev_for_each(rdev, mddev)
  				if (rdev->raid_disk >= 0 &&
  				    !test_bit(Journal, &rdev->flags) &&
  				    !test_bit(In_sync, &rdev->flags) &&
  				    rdev->recovery_offset < sector_nr)
  					rdev->recovery_offset = sector_nr;
  		conf->reshape_checkpoint = jiffies;
  		set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
  		md_wakeup_thread(mddev->thread);
  		wait_event(mddev->sb_wait,
  			   !test_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags)
  			   || test_bit(MD_RECOVERY_INTR, &mddev->recovery));
  		if (test_bit(MD_RECOVERY_INTR, &mddev->recovery))
  			goto ret;
  		spin_lock_irq(&conf->device_lock);
  		conf->reshape_safe = mddev->reshape_position;
  		spin_unlock_irq(&conf->device_lock);
  		wake_up(&conf->wait_for_overlap);
  		sysfs_notify_dirent_safe(mddev->sysfs_completed);
  	}
  ret:
  	return retn;
  }
  
  static inline sector_t raid5_sync_request(struct mddev *mddev, sector_t sector_nr,
  					  int *skipped)
  {
  	struct r5conf *conf = mddev->private;
  	struct stripe_head *sh;
  	sector_t max_sector = mddev->dev_sectors;
  	sector_t sync_blocks;
  	int still_degraded = 0;
  	int i;
  
  	if (sector_nr >= max_sector) {
  		/* just being told to finish up .. nothing much to do */
  
  		if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery)) {
  			end_reshape(conf);
  			return 0;
  		}
  
  		if (mddev->curr_resync < max_sector) /* aborted */
  			md_bitmap_end_sync(mddev->bitmap, mddev->curr_resync,
  					   &sync_blocks, 1);
  		else /* completed sync */
  			conf->fullsync = 0;
  		md_bitmap_close_sync(mddev->bitmap);
  
  		return 0;
  	}
  
  	/* Allow raid5_quiesce to complete */
  	wait_event(conf->wait_for_overlap, conf->quiesce != 2);
  
  	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
  		return reshape_request(mddev, sector_nr, skipped);
  
  	/* No need to check resync_max as we never do more than one
  	 * stripe, and as resync_max will always be on a chunk boundary,
  	 * if the check in md_do_sync didn't fire, there is no chance
  	 * of overstepping resync_max here
  	 */
  
  	/* if there is too many failed drives and we are trying
  	 * to resync, then assert that we are finished, because there is
  	 * nothing we can do.
  	 */
  	if (mddev->degraded >= conf->max_degraded &&
  	    test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
  		sector_t rv = mddev->dev_sectors - sector_nr;
  		*skipped = 1;
  		return rv;
  	}
  	if (!test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) &&
  	    !conf->fullsync &&
  	    !md_bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1) &&
  	    sync_blocks >= RAID5_STRIPE_SECTORS(conf)) {
  		/* we can skip this block, and probably more */
  		do_div(sync_blocks, RAID5_STRIPE_SECTORS(conf));
  		*skipped = 1;
  		/* keep things rounded to whole stripes */
  		return sync_blocks * RAID5_STRIPE_SECTORS(conf);
  	}
  
  	md_bitmap_cond_end_sync(mddev->bitmap, sector_nr, false);
  
  	sh = raid5_get_active_stripe(conf, sector_nr, 0, 1, 0);
  	if (sh == NULL) {
  		sh = raid5_get_active_stripe(conf, sector_nr, 0, 0, 0);
  		/* make sure we don't swamp the stripe cache if someone else
  		 * is trying to get access
  		 */
  		schedule_timeout_uninterruptible(1);
  	}
  	/* Need to check if array will still be degraded after recovery/resync
  	 * Note in case of > 1 drive failures it's possible we're rebuilding
  	 * one drive while leaving another faulty drive in array.
  	 */
  	rcu_read_lock();
  	for (i = 0; i < conf->raid_disks; i++) {
  		struct md_rdev *rdev = READ_ONCE(conf->disks[i].rdev);
  
  		if (rdev == NULL || test_bit(Faulty, &rdev->flags))
  			still_degraded = 1;
  	}
  	rcu_read_unlock();
  
  	md_bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, still_degraded);
  
  	set_bit(STRIPE_SYNC_REQUESTED, &sh->state);
  	set_bit(STRIPE_HANDLE, &sh->state);
  
  	raid5_release_stripe(sh);
  
  	return RAID5_STRIPE_SECTORS(conf);
  }
  
  static int  retry_aligned_read(struct r5conf *conf, struct bio *raid_bio,
  			       unsigned int offset)
  {
  	/* We may not be able to submit a whole bio at once as there
  	 * may not be enough stripe_heads available.
  	 * We cannot pre-allocate enough stripe_heads as we may need
  	 * more than exist in the cache (if we allow ever large chunks).
  	 * So we do one stripe head at a time and record in
  	 * ->bi_hw_segments how many have been done.
  	 *
  	 * We *know* that this entire raid_bio is in one chunk, so
  	 * it will be only one 'dd_idx' and only need one call to raid5_compute_sector.
  	 */
  	struct stripe_head *sh;
  	int dd_idx;
  	sector_t sector, logical_sector, last_sector;
  	int scnt = 0;
  	int handled = 0;
  
  	logical_sector = raid_bio->bi_iter.bi_sector &
  		~((sector_t)RAID5_STRIPE_SECTORS(conf)-1);
  	sector = raid5_compute_sector(conf, logical_sector,
  				      0, &dd_idx, NULL);
  	last_sector = bio_end_sector(raid_bio);
  
  	for (; logical_sector < last_sector;
  	     logical_sector += RAID5_STRIPE_SECTORS(conf),
  		     sector += RAID5_STRIPE_SECTORS(conf),
  		     scnt++) {
  
  		if (scnt < offset)
  			/* already done this stripe */
  			continue;
  
  		sh = raid5_get_active_stripe(conf, sector, 0, 1, 1);
  
  		if (!sh) {
  			/* failed to get a stripe - must wait */
  			conf->retry_read_aligned = raid_bio;
  			conf->retry_read_offset = scnt;
  			return handled;
  		}
  
  		if (!add_stripe_bio(sh, raid_bio, dd_idx, 0, 0)) {
  			raid5_release_stripe(sh);
  			conf->retry_read_aligned = raid_bio;
  			conf->retry_read_offset = scnt;
  			return handled;
  		}
  
  		set_bit(R5_ReadNoMerge, &sh->dev[dd_idx].flags);
  		handle_stripe(sh);
  		raid5_release_stripe(sh);
  		handled++;
  	}
  
  	bio_endio(raid_bio);
  
  	if (atomic_dec_and_test(&conf->active_aligned_reads))
  		wake_up(&conf->wait_for_quiescent);
  	return handled;
  }
  
  static int handle_active_stripes(struct r5conf *conf, int group,
  				 struct r5worker *worker,
  				 struct list_head *temp_inactive_list)
  		__releases(&conf->device_lock)
  		__acquires(&conf->device_lock)
  {
  	struct stripe_head *batch[MAX_STRIPE_BATCH], *sh;
  	int i, batch_size = 0, hash;
  	bool release_inactive = false;
  
  	while (batch_size < MAX_STRIPE_BATCH &&
  			(sh = __get_priority_stripe(conf, group)) != NULL)
  		batch[batch_size++] = sh;
  
  	if (batch_size == 0) {
  		for (i = 0; i < NR_STRIPE_HASH_LOCKS; i++)
  			if (!list_empty(temp_inactive_list + i))
  				break;
  		if (i == NR_STRIPE_HASH_LOCKS) {
  			spin_unlock_irq(&conf->device_lock);
  			log_flush_stripe_to_raid(conf);
  			spin_lock_irq(&conf->device_lock);
  			return batch_size;
  		}
  		release_inactive = true;
  	}
  	spin_unlock_irq(&conf->device_lock);
  
  	release_inactive_stripe_list(conf, temp_inactive_list,
  				     NR_STRIPE_HASH_LOCKS);
  
  	r5l_flush_stripe_to_raid(conf->log);
  	if (release_inactive) {
  		spin_lock_irq(&conf->device_lock);
  		return 0;
  	}
  
  	for (i = 0; i < batch_size; i++)
  		handle_stripe(batch[i]);
  	log_write_stripe_run(conf);
  
  	cond_resched();
  
  	spin_lock_irq(&conf->device_lock);
  	for (i = 0; i < batch_size; i++) {
  		hash = batch[i]->hash_lock_index;
  		__release_stripe(conf, batch[i], &temp_inactive_list[hash]);
  	}
  	return batch_size;
  }
  
  static void raid5_do_work(struct work_struct *work)
  {
  	struct r5worker *worker = container_of(work, struct r5worker, work);
  	struct r5worker_group *group = worker->group;
  	struct r5conf *conf = group->conf;
  	struct mddev *mddev = conf->mddev;
  	int group_id = group - conf->worker_groups;
  	int handled;
  	struct blk_plug plug;
  
  	pr_debug("+++ raid5worker active\n");
  
  	blk_start_plug(&plug);
  	handled = 0;
  	spin_lock_irq(&conf->device_lock);
  	while (1) {
  		int batch_size, released;
  
  		released = release_stripe_list(conf, worker->temp_inactive_list);
  
  		batch_size = handle_active_stripes(conf, group_id, worker,
  						   worker->temp_inactive_list);
  		worker->working = false;
  		if (!batch_size && !released)
  			break;
  		handled += batch_size;
  		wait_event_lock_irq(mddev->sb_wait,
  			!test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags),
  			conf->device_lock);
  	}
  	pr_debug("%d stripes handled\n", handled);
  
  	spin_unlock_irq(&conf->device_lock);
  
  	flush_deferred_bios(conf);
  
  	r5l_flush_stripe_to_raid(conf->log);
  
  	async_tx_issue_pending_all();
  	blk_finish_plug(&plug);
  
  	pr_debug("--- raid5worker inactive\n");
  }
  
  /*
   * This is our raid5 kernel thread.
   *
   * We scan the hash table for stripes which can be handled now.
   * During the scan, completed stripes are saved for us by the interrupt
   * handler, so that they will not have to wait for our next wakeup.
   */
  static void raid5d(struct md_thread *thread)
  {
  	struct mddev *mddev = thread->mddev;
  	struct r5conf *conf = mddev->private;
  	int handled;
  	struct blk_plug plug;
  
  	pr_debug("+++ raid5d active\n");
  
  	md_check_recovery(mddev);
  
  	blk_start_plug(&plug);
  	handled = 0;
  	spin_lock_irq(&conf->device_lock);
  	while (1) {
  		struct bio *bio;
  		int batch_size, released;
  		unsigned int offset;
  
  		released = release_stripe_list(conf, conf->temp_inactive_list);
  		if (released)
  			clear_bit(R5_DID_ALLOC, &conf->cache_state);
  
  		if (
  		    !list_empty(&conf->bitmap_list)) {
  			/* Now is a good time to flush some bitmap updates */
  			conf->seq_flush++;
  			spin_unlock_irq(&conf->device_lock);
  			md_bitmap_unplug(mddev->bitmap);
  			spin_lock_irq(&conf->device_lock);
  			conf->seq_write = conf->seq_flush;
  			activate_bit_delay(conf, conf->temp_inactive_list);
  		}
  		raid5_activate_delayed(conf);
  
  		while ((bio = remove_bio_from_retry(conf, &offset))) {
  			int ok;
  			spin_unlock_irq(&conf->device_lock);
  			ok = retry_aligned_read(conf, bio, offset);
  			spin_lock_irq(&conf->device_lock);
  			if (!ok)
  				break;
  			handled++;
  		}
  
  		batch_size = handle_active_stripes(conf, ANY_GROUP, NULL,
  						   conf->temp_inactive_list);
  		if (!batch_size && !released)
  			break;
  		handled += batch_size;
  
  		if (mddev->sb_flags & ~(1 << MD_SB_CHANGE_PENDING)) {
  			spin_unlock_irq(&conf->device_lock);
  			md_check_recovery(mddev);
  			spin_lock_irq(&conf->device_lock);
  		}
  	}
  	pr_debug("%d stripes handled\n", handled);
  
  	spin_unlock_irq(&conf->device_lock);
  	if (test_and_clear_bit(R5_ALLOC_MORE, &conf->cache_state) &&
  	    mutex_trylock(&conf->cache_size_mutex)) {
  		grow_one_stripe(conf, __GFP_NOWARN);
  		/* Set flag even if allocation failed.  This helps
  		 * slow down allocation requests when mem is short
  		 */
  		set_bit(R5_DID_ALLOC, &conf->cache_state);
  		mutex_unlock(&conf->cache_size_mutex);
  	}
  
  	flush_deferred_bios(conf);
  
  	r5l_flush_stripe_to_raid(conf->log);
  
  	async_tx_issue_pending_all();
  	blk_finish_plug(&plug);
  
  	pr_debug("--- raid5d inactive\n");
  }
  
  static ssize_t
  raid5_show_stripe_cache_size(struct mddev *mddev, char *page)
  {
  	struct r5conf *conf;
  	int ret = 0;
  	spin_lock(&mddev->lock);
  	conf = mddev->private;
  	if (conf)
  		ret = sprintf(page, "%d\n", conf->min_nr_stripes);
  	spin_unlock(&mddev->lock);
  	return ret;
  }
  
  int
  raid5_set_cache_size(struct mddev *mddev, int size)
  {
  	int result = 0;
  	struct r5conf *conf = mddev->private;
  
  	if (size <= 16 || size > 32768)
  		return -EINVAL;
  
  	conf->min_nr_stripes = size;
  	mutex_lock(&conf->cache_size_mutex);
  	while (size < conf->max_nr_stripes &&
  	       drop_one_stripe(conf))
  		;
  	mutex_unlock(&conf->cache_size_mutex);
  
  	md_allow_write(mddev);
  
  	mutex_lock(&conf->cache_size_mutex);
  	while (size > conf->max_nr_stripes)
  		if (!grow_one_stripe(conf, GFP_KERNEL)) {
  			conf->min_nr_stripes = conf->max_nr_stripes;
  			result = -ENOMEM;
  			break;
  		}
  	mutex_unlock(&conf->cache_size_mutex);
  
  	return result;
  }
  EXPORT_SYMBOL(raid5_set_cache_size);
  
  static ssize_t
  raid5_store_stripe_cache_size(struct mddev *mddev, const char *page, size_t len)
  {
  	struct r5conf *conf;
  	unsigned long new;
  	int err;
  
  	if (len >= PAGE_SIZE)
  		return -EINVAL;
  	if (kstrtoul(page, 10, &new))
  		return -EINVAL;
  	err = mddev_lock(mddev);
  	if (err)
  		return err;
  	conf = mddev->private;
  	if (!conf)
  		err = -ENODEV;
  	else
  		err = raid5_set_cache_size(mddev, new);
  	mddev_unlock(mddev);
  
  	return err ?: len;
  }
  
  static struct md_sysfs_entry
  raid5_stripecache_size = __ATTR(stripe_cache_size, S_IRUGO | S_IWUSR,
  				raid5_show_stripe_cache_size,
  				raid5_store_stripe_cache_size);
  
  static ssize_t
  raid5_show_rmw_level(struct mddev  *mddev, char *page)
  {
  	struct r5conf *conf = mddev->private;
  	if (conf)
  		return sprintf(page, "%d\n", conf->rmw_level);
  	else
  		return 0;
  }
  
  static ssize_t
  raid5_store_rmw_level(struct mddev  *mddev, const char *page, size_t len)
  {
  	struct r5conf *conf = mddev->private;
  	unsigned long new;
  
  	if (!conf)
  		return -ENODEV;
  
  	if (len >= PAGE_SIZE)
  		return -EINVAL;
  
  	if (kstrtoul(page, 10, &new))
  		return -EINVAL;
  
  	if (new != PARITY_DISABLE_RMW && !raid6_call.xor_syndrome)
  		return -EINVAL;
  
  	if (new != PARITY_DISABLE_RMW &&
  	    new != PARITY_ENABLE_RMW &&
  	    new != PARITY_PREFER_RMW)
  		return -EINVAL;
  
  	conf->rmw_level = new;
  	return len;
  }
  
  static struct md_sysfs_entry
  raid5_rmw_level = __ATTR(rmw_level, S_IRUGO | S_IWUSR,
  			 raid5_show_rmw_level,
  			 raid5_store_rmw_level);
  
  static ssize_t
  raid5_show_stripe_size(struct mddev  *mddev, char *page)
  {
  	struct r5conf *conf;
  	int ret = 0;
  
  	spin_lock(&mddev->lock);
  	conf = mddev->private;
  	if (conf)
  		ret = sprintf(page, "%lu\n", RAID5_STRIPE_SIZE(conf));
  	spin_unlock(&mddev->lock);
  	return ret;
  }
  
  #if PAGE_SIZE != DEFAULT_STRIPE_SIZE
  static ssize_t
  raid5_store_stripe_size(struct mddev  *mddev, const char *page, size_t len)
  {
  	struct r5conf *conf;
  	unsigned long new;
  	int err;
  	int size;
  
  	if (len >= PAGE_SIZE)
  		return -EINVAL;
  	if (kstrtoul(page, 10, &new))
  		return -EINVAL;
  
  	/*
  	 * The value should not be bigger than PAGE_SIZE. It requires to
  	 * be multiple of DEFAULT_STRIPE_SIZE and the value should be power
  	 * of two.
  	 */
  	if (new % DEFAULT_STRIPE_SIZE != 0 ||
  			new > PAGE_SIZE || new == 0 ||
  			new != roundup_pow_of_two(new))
  		return -EINVAL;
  
  	err = mddev_lock(mddev);
  	if (err)
  		return err;
  
  	conf = mddev->private;
  	if (!conf) {
  		err = -ENODEV;
  		goto out_unlock;
  	}
  
  	if (new == conf->stripe_size)
  		goto out_unlock;
  
  	pr_debug("md/raid: change stripe_size from %lu to %lu\n",
  			conf->stripe_size, new);
  
  	if (mddev->sync_thread ||
  		test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
  		mddev->reshape_position != MaxSector ||
  		mddev->sysfs_active) {
  		err = -EBUSY;
  		goto out_unlock;
  	}
  
  	mddev_suspend(mddev);
  	mutex_lock(&conf->cache_size_mutex);
  	size = conf->max_nr_stripes;
  
  	shrink_stripes(conf);
  
  	conf->stripe_size = new;
  	conf->stripe_shift = ilog2(new) - 9;
  	conf->stripe_sectors = new >> 9;
  	if (grow_stripes(conf, size)) {
  		pr_warn("md/raid:%s: couldn't allocate buffers\n",
  				mdname(mddev));
  		err = -ENOMEM;
  	}
  	mutex_unlock(&conf->cache_size_mutex);
  	mddev_resume(mddev);
  
  out_unlock:
  	mddev_unlock(mddev);
  	return err ?: len;
  }
  
  static struct md_sysfs_entry
  raid5_stripe_size = __ATTR(stripe_size, 0644,
  			 raid5_show_stripe_size,
  			 raid5_store_stripe_size);
  #else
  static struct md_sysfs_entry
  raid5_stripe_size = __ATTR(stripe_size, 0444,
  			 raid5_show_stripe_size,
  			 NULL);
  #endif
  
  static ssize_t
  raid5_show_preread_threshold(struct mddev *mddev, char *page)
  {
  	struct r5conf *conf;
  	int ret = 0;
  	spin_lock(&mddev->lock);
  	conf = mddev->private;
  	if (conf)
  		ret = sprintf(page, "%d\n", conf->bypass_threshold);
  	spin_unlock(&mddev->lock);
  	return ret;
  }
  
  static ssize_t
  raid5_store_preread_threshold(struct mddev *mddev, const char *page, size_t len)
  {
  	struct r5conf *conf;
  	unsigned long new;
  	int err;
  
  	if (len >= PAGE_SIZE)
  		return -EINVAL;
  	if (kstrtoul(page, 10, &new))
  		return -EINVAL;
  
  	err = mddev_lock(mddev);
  	if (err)
  		return err;
  	conf = mddev->private;
  	if (!conf)
  		err = -ENODEV;
  	else if (new > conf->min_nr_stripes)
  		err = -EINVAL;
  	else
  		conf->bypass_threshold = new;
  	mddev_unlock(mddev);
  	return err ?: len;
  }
  
  static struct md_sysfs_entry
  raid5_preread_bypass_threshold = __ATTR(preread_bypass_threshold,
  					S_IRUGO | S_IWUSR,
  					raid5_show_preread_threshold,
  					raid5_store_preread_threshold);
  
  static ssize_t
  raid5_show_skip_copy(struct mddev *mddev, char *page)
  {
  	struct r5conf *conf;
  	int ret = 0;
  	spin_lock(&mddev->lock);
  	conf = mddev->private;
  	if (conf)
  		ret = sprintf(page, "%d\n", conf->skip_copy);
  	spin_unlock(&mddev->lock);
  	return ret;
  }
  
  static ssize_t
  raid5_store_skip_copy(struct mddev *mddev, const char *page, size_t len)
  {
  	struct r5conf *conf;
  	unsigned long new;
  	int err;
  
  	if (len >= PAGE_SIZE)
  		return -EINVAL;
  	if (kstrtoul(page, 10, &new))
  		return -EINVAL;
  	new = !!new;
  
  	err = mddev_lock(mddev);
  	if (err)
  		return err;
  	conf = mddev->private;
  	if (!conf)
  		err = -ENODEV;
  	else if (new != conf->skip_copy) {
  		struct request_queue *q = mddev->queue;
  
  		mddev_suspend(mddev);
  		conf->skip_copy = new;
  		if (new)
  			blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES, q);
  		else
  			blk_queue_flag_clear(QUEUE_FLAG_STABLE_WRITES, q);
  		mddev_resume(mddev);
  	}
  	mddev_unlock(mddev);
  	return err ?: len;
  }
  
  static struct md_sysfs_entry
  raid5_skip_copy = __ATTR(skip_copy, S_IRUGO | S_IWUSR,
  					raid5_show_skip_copy,
  					raid5_store_skip_copy);
  
  static ssize_t
  stripe_cache_active_show(struct mddev *mddev, char *page)
  {
  	struct r5conf *conf = mddev->private;
  	if (conf)
  		return sprintf(page, "%d\n", atomic_read(&conf->active_stripes));
  	else
  		return 0;
  }
  
  static struct md_sysfs_entry
  raid5_stripecache_active = __ATTR_RO(stripe_cache_active);
  
  static ssize_t
  raid5_show_group_thread_cnt(struct mddev *mddev, char *page)
  {
  	struct r5conf *conf;
  	int ret = 0;
  	spin_lock(&mddev->lock);
  	conf = mddev->private;
  	if (conf)
  		ret = sprintf(page, "%d\n", conf->worker_cnt_per_group);
  	spin_unlock(&mddev->lock);
  	return ret;
  }
  
  static int alloc_thread_groups(struct r5conf *conf, int cnt,
  			       int *group_cnt,
  			       struct r5worker_group **worker_groups);
  static ssize_t
  raid5_store_group_thread_cnt(struct mddev *mddev, const char *page, size_t len)
  {
  	struct r5conf *conf;
  	unsigned int new;
  	int err;
  	struct r5worker_group *new_groups, *old_groups;
  	int group_cnt;
  
  	if (len >= PAGE_SIZE)
  		return -EINVAL;
  	if (kstrtouint(page, 10, &new))
  		return -EINVAL;
  	/* 8192 should be big enough */
  	if (new > 8192)
  		return -EINVAL;
  
  	err = mddev_lock(mddev);
  	if (err)
  		return err;
  	conf = mddev->private;
  	if (!conf)
  		err = -ENODEV;
  	else if (new != conf->worker_cnt_per_group) {
  		mddev_suspend(mddev);
  
  		old_groups = conf->worker_groups;
  		if (old_groups)
  			flush_workqueue(raid5_wq);
  
  		err = alloc_thread_groups(conf, new, &group_cnt, &new_groups);
  		if (!err) {
  			spin_lock_irq(&conf->device_lock);
  			conf->group_cnt = group_cnt;
  			conf->worker_cnt_per_group = new;
  			conf->worker_groups = new_groups;
  			spin_unlock_irq(&conf->device_lock);
  
  			if (old_groups)
  				kfree(old_groups[0].workers);
  			kfree(old_groups);
  		}
  		mddev_resume(mddev);
  	}
  	mddev_unlock(mddev);
  
  	return err ?: len;
  }
  
  static struct md_sysfs_entry
  raid5_group_thread_cnt = __ATTR(group_thread_cnt, S_IRUGO | S_IWUSR,
  				raid5_show_group_thread_cnt,
  				raid5_store_group_thread_cnt);
  
  static struct attribute *raid5_attrs[] =  {
  	&raid5_stripecache_size.attr,
  	&raid5_stripecache_active.attr,
  	&raid5_preread_bypass_threshold.attr,
  	&raid5_group_thread_cnt.attr,
  	&raid5_skip_copy.attr,
  	&raid5_rmw_level.attr,
  	&raid5_stripe_size.attr,
  	&r5c_journal_mode.attr,
  	&ppl_write_hint.attr,
  	NULL,
  };
  static struct attribute_group raid5_attrs_group = {
  	.name = NULL,
  	.attrs = raid5_attrs,
  };
  
  static int alloc_thread_groups(struct r5conf *conf, int cnt, int *group_cnt,
  			       struct r5worker_group **worker_groups)
  {
  	int i, j, k;
  	ssize_t size;
  	struct r5worker *workers;
  
  	if (cnt == 0) {
  		*group_cnt = 0;
  		*worker_groups = NULL;
  		return 0;
  	}
  	*group_cnt = num_possible_nodes();
  	size = sizeof(struct r5worker) * cnt;
  	workers = kcalloc(size, *group_cnt, GFP_NOIO);
  	*worker_groups = kcalloc(*group_cnt, sizeof(struct r5worker_group),
  				 GFP_NOIO);
  	if (!*worker_groups || !workers) {
  		kfree(workers);
  		kfree(*worker_groups);
  		return -ENOMEM;
  	}
  
  	for (i = 0; i < *group_cnt; i++) {
  		struct r5worker_group *group;
  
  		group = &(*worker_groups)[i];
  		INIT_LIST_HEAD(&group->handle_list);
  		INIT_LIST_HEAD(&group->loprio_list);
  		group->conf = conf;
  		group->workers = workers + i * cnt;
  
  		for (j = 0; j < cnt; j++) {
  			struct r5worker *worker = group->workers + j;
  			worker->group = group;
  			INIT_WORK(&worker->work, raid5_do_work);
  
  			for (k = 0; k < NR_STRIPE_HASH_LOCKS; k++)
  				INIT_LIST_HEAD(worker->temp_inactive_list + k);
  		}
  	}
  
  	return 0;
  }
  
  static void free_thread_groups(struct r5conf *conf)
  {
  	if (conf->worker_groups)
  		kfree(conf->worker_groups[0].workers);
  	kfree(conf->worker_groups);
  	conf->worker_groups = NULL;
  }
  
  static sector_t
  raid5_size(struct mddev *mddev, sector_t sectors, int raid_disks)
  {
  	struct r5conf *conf = mddev->private;
  
  	if (!sectors)
  		sectors = mddev->dev_sectors;
  	if (!raid_disks)
  		/* size is defined by the smallest of previous and new size */
  		raid_disks = min(conf->raid_disks, conf->previous_raid_disks);
  
  	sectors &= ~((sector_t)conf->chunk_sectors - 1);
  	sectors &= ~((sector_t)conf->prev_chunk_sectors - 1);
  	return sectors * (raid_disks - conf->max_degraded);
  }
  
  static void free_scratch_buffer(struct r5conf *conf, struct raid5_percpu *percpu)
  {
  	safe_put_page(percpu->spare_page);
  	percpu->spare_page = NULL;
  	kvfree(percpu->scribble);
  	percpu->scribble = NULL;
  }
  
  static int alloc_scratch_buffer(struct r5conf *conf, struct raid5_percpu *percpu)
  {
  	if (conf->level == 6 && !percpu->spare_page) {
  		percpu->spare_page = alloc_page(GFP_KERNEL);
  		if (!percpu->spare_page)
  			return -ENOMEM;
  	}
  
  	if (scribble_alloc(percpu,
  			   max(conf->raid_disks,
  			       conf->previous_raid_disks),
  			   max(conf->chunk_sectors,
  			       conf->prev_chunk_sectors)
  			   / RAID5_STRIPE_SECTORS(conf))) {
  		free_scratch_buffer(conf, percpu);
  		return -ENOMEM;
  	}
  
  	return 0;
  }
  
  static int raid456_cpu_dead(unsigned int cpu, struct hlist_node *node)
  {
  	struct r5conf *conf = hlist_entry_safe(node, struct r5conf, node);
  
  	free_scratch_buffer(conf, per_cpu_ptr(conf->percpu, cpu));
  	return 0;
  }
  
  static void raid5_free_percpu(struct r5conf *conf)
  {
  	if (!conf->percpu)
  		return;
  
  	cpuhp_state_remove_instance(CPUHP_MD_RAID5_PREPARE, &conf->node);
  	free_percpu(conf->percpu);
  }
  
  static void free_conf(struct r5conf *conf)
  {
  	int i;
  
  	log_exit(conf);
  
  	unregister_shrinker(&conf->shrinker);
  	free_thread_groups(conf);
  	shrink_stripes(conf);
  	raid5_free_percpu(conf);
  	for (i = 0; i < conf->pool_size; i++)
  		if (conf->disks[i].extra_page)
  			put_page(conf->disks[i].extra_page);
  	kfree(conf->disks);
  	bioset_exit(&conf->bio_split);
  	kfree(conf->stripe_hashtbl);
  	kfree(conf->pending_data);
  	kfree(conf);
  }
  
  static int raid456_cpu_up_prepare(unsigned int cpu, struct hlist_node *node)
  {
  	struct r5conf *conf = hlist_entry_safe(node, struct r5conf, node);
  	struct raid5_percpu *percpu = per_cpu_ptr(conf->percpu, cpu);
  
  	if (alloc_scratch_buffer(conf, percpu)) {
  		pr_warn("%s: failed memory allocation for cpu%u\n",
  			__func__, cpu);
  		return -ENOMEM;
  	}
  	spin_lock_init(&per_cpu_ptr(conf->percpu, cpu)->lock);
  	return 0;
  }
  
  static int raid5_alloc_percpu(struct r5conf *conf)
  {
  	int err = 0;
  
  	conf->percpu = alloc_percpu(struct raid5_percpu);
  	if (!conf->percpu)
  		return -ENOMEM;
  
  	err = cpuhp_state_add_instance(CPUHP_MD_RAID5_PREPARE, &conf->node);
  	if (!err) {
  		conf->scribble_disks = max(conf->raid_disks,
  			conf->previous_raid_disks);
  		conf->scribble_sectors = max(conf->chunk_sectors,
  			conf->prev_chunk_sectors);
  	}
  	return err;
  }
  
  static unsigned long raid5_cache_scan(struct shrinker *shrink,
  				      struct shrink_control *sc)
  {
  	struct r5conf *conf = container_of(shrink, struct r5conf, shrinker);
  	unsigned long ret = SHRINK_STOP;
  
  	if (mutex_trylock(&conf->cache_size_mutex)) {
  		ret= 0;
  		while (ret < sc->nr_to_scan &&
  		       conf->max_nr_stripes > conf->min_nr_stripes) {
  			if (drop_one_stripe(conf) == 0) {
  				ret = SHRINK_STOP;
  				break;
  			}
  			ret++;
  		}
  		mutex_unlock(&conf->cache_size_mutex);
  	}
  	return ret;
  }
  
  static unsigned long raid5_cache_count(struct shrinker *shrink,
  				       struct shrink_control *sc)
  {
  	struct r5conf *conf = container_of(shrink, struct r5conf, shrinker);
  
  	if (conf->max_nr_stripes < conf->min_nr_stripes)
  		/* unlikely, but not impossible */
  		return 0;
  	return conf->max_nr_stripes - conf->min_nr_stripes;
  }
  
  static struct r5conf *setup_conf(struct mddev *mddev)
  {
  	struct r5conf *conf;
  	int raid_disk, memory, max_disks;
  	struct md_rdev *rdev;
  	struct disk_info *disk;
  	char pers_name[6];
  	int i;
  	int group_cnt;
  	struct r5worker_group *new_group;
  	int ret;
  
  	if (mddev->new_level != 5
  	    && mddev->new_level != 4
  	    && mddev->new_level != 6) {
  		pr_warn("md/raid:%s: raid level not set to 4/5/6 (%d)\n",
  			mdname(mddev), mddev->new_level);
  		return ERR_PTR(-EIO);
  	}
  	if ((mddev->new_level == 5
  	     && !algorithm_valid_raid5(mddev->new_layout)) ||
  	    (mddev->new_level == 6
  	     && !algorithm_valid_raid6(mddev->new_layout))) {
  		pr_warn("md/raid:%s: layout %d not supported\n",
  			mdname(mddev), mddev->new_layout);
  		return ERR_PTR(-EIO);
  	}
  	if (mddev->new_level == 6 && mddev->raid_disks < 4) {
  		pr_warn("md/raid:%s: not enough configured devices (%d, minimum 4)\n",
  			mdname(mddev), mddev->raid_disks);
  		return ERR_PTR(-EINVAL);
  	}
  
  	if (!mddev->new_chunk_sectors ||
  	    (mddev->new_chunk_sectors << 9) % PAGE_SIZE ||
  	    !is_power_of_2(mddev->new_chunk_sectors)) {
  		pr_warn("md/raid:%s: invalid chunk size %d\n",
  			mdname(mddev), mddev->new_chunk_sectors << 9);
  		return ERR_PTR(-EINVAL);
  	}
  
  	conf = kzalloc(sizeof(struct r5conf), GFP_KERNEL);
  	if (conf == NULL)
  		goto abort;
  
  #if PAGE_SIZE != DEFAULT_STRIPE_SIZE
  	conf->stripe_size = DEFAULT_STRIPE_SIZE;
  	conf->stripe_shift = ilog2(DEFAULT_STRIPE_SIZE) - 9;
  	conf->stripe_sectors = DEFAULT_STRIPE_SIZE >> 9;
  #endif
  	INIT_LIST_HEAD(&conf->free_list);
  	INIT_LIST_HEAD(&conf->pending_list);
  	conf->pending_data = kcalloc(PENDING_IO_MAX,
  				     sizeof(struct r5pending_data),
  				     GFP_KERNEL);
  	if (!conf->pending_data)
  		goto abort;
  	for (i = 0; i < PENDING_IO_MAX; i++)
  		list_add(&conf->pending_data[i].sibling, &conf->free_list);
  	/* Don't enable multi-threading by default*/
  	if (!alloc_thread_groups(conf, 0, &group_cnt, &new_group)) {
  		conf->group_cnt = group_cnt;
  		conf->worker_cnt_per_group = 0;
  		conf->worker_groups = new_group;
  	} else
  		goto abort;
  	spin_lock_init(&conf->device_lock);
  	seqcount_spinlock_init(&conf->gen_lock, &conf->device_lock);
  	mutex_init(&conf->cache_size_mutex);
  	init_waitqueue_head(&conf->wait_for_quiescent);
  	init_waitqueue_head(&conf->wait_for_stripe);
  	init_waitqueue_head(&conf->wait_for_overlap);
  	INIT_LIST_HEAD(&conf->handle_list);
  	INIT_LIST_HEAD(&conf->loprio_list);
  	INIT_LIST_HEAD(&conf->hold_list);
  	INIT_LIST_HEAD(&conf->delayed_list);
  	INIT_LIST_HEAD(&conf->bitmap_list);
  	init_llist_head(&conf->released_stripes);
  	atomic_set(&conf->active_stripes, 0);
  	atomic_set(&conf->preread_active_stripes, 0);
  	atomic_set(&conf->active_aligned_reads, 0);
  	spin_lock_init(&conf->pending_bios_lock);
  	conf->batch_bio_dispatch = true;
  	rdev_for_each(rdev, mddev) {
  		if (test_bit(Journal, &rdev->flags))
  			continue;
  		if (blk_queue_nonrot(bdev_get_queue(rdev->bdev))) {
  			conf->batch_bio_dispatch = false;
  			break;
  		}
  	}
  
  	conf->bypass_threshold = BYPASS_THRESHOLD;
  	conf->recovery_disabled = mddev->recovery_disabled - 1;
  
  	conf->raid_disks = mddev->raid_disks;
  	if (mddev->reshape_position == MaxSector)
  		conf->previous_raid_disks = mddev->raid_disks;
  	else
  		conf->previous_raid_disks = mddev->raid_disks - mddev->delta_disks;
  	max_disks = max(conf->raid_disks, conf->previous_raid_disks);
  
  	conf->disks = kcalloc(max_disks, sizeof(struct disk_info),
  			      GFP_KERNEL);
  
  	if (!conf->disks)
  		goto abort;
  
  	for (i = 0; i < max_disks; i++) {
  		conf->disks[i].extra_page = alloc_page(GFP_KERNEL);
  		if (!conf->disks[i].extra_page)
  			goto abort;
  	}
  
  	ret = bioset_init(&conf->bio_split, BIO_POOL_SIZE, 0, 0);
  	if (ret)
  		goto abort;
  	conf->mddev = mddev;
  
  	if ((conf->stripe_hashtbl = kzalloc(PAGE_SIZE, GFP_KERNEL)) == NULL)
  		goto abort;
  
  	/* We init hash_locks[0] separately to that it can be used
  	 * as the reference lock in the spin_lock_nest_lock() call
  	 * in lock_all_device_hash_locks_irq in order to convince
  	 * lockdep that we know what we are doing.
  	 */
  	spin_lock_init(conf->hash_locks);
  	for (i = 1; i < NR_STRIPE_HASH_LOCKS; i++)
  		spin_lock_init(conf->hash_locks + i);
  
  	for (i = 0; i < NR_STRIPE_HASH_LOCKS; i++)
  		INIT_LIST_HEAD(conf->inactive_list + i);
  
  	for (i = 0; i < NR_STRIPE_HASH_LOCKS; i++)
  		INIT_LIST_HEAD(conf->temp_inactive_list + i);
  
  	atomic_set(&conf->r5c_cached_full_stripes, 0);
  	INIT_LIST_HEAD(&conf->r5c_full_stripe_list);
  	atomic_set(&conf->r5c_cached_partial_stripes, 0);
  	INIT_LIST_HEAD(&conf->r5c_partial_stripe_list);
  	atomic_set(&conf->r5c_flushing_full_stripes, 0);
  	atomic_set(&conf->r5c_flushing_partial_stripes, 0);
  
  	conf->level = mddev->new_level;
  	conf->chunk_sectors = mddev->new_chunk_sectors;
  	if (raid5_alloc_percpu(conf) != 0)
  		goto abort;
  
  	pr_debug("raid456: run(%s) called.\n", mdname(mddev));
  
  	rdev_for_each(rdev, mddev) {
  		raid_disk = rdev->raid_disk;
  		if (raid_disk >= max_disks
  		    || raid_disk < 0 || test_bit(Journal, &rdev->flags))
  			continue;
  		disk = conf->disks + raid_disk;
  
  		if (test_bit(Replacement, &rdev->flags)) {
  			if (disk->replacement)
  				goto abort;
  			disk->replacement = rdev;
  		} else {
  			if (disk->rdev)
  				goto abort;
  			disk->rdev = rdev;
  		}
  
  		if (test_bit(In_sync, &rdev->flags)) {
  			char b[BDEVNAME_SIZE];
  			pr_info("md/raid:%s: device %s operational as raid disk %d\n",
  				mdname(mddev), bdevname(rdev->bdev, b), raid_disk);
  		} else if (rdev->saved_raid_disk != raid_disk)
  			/* Cannot rely on bitmap to complete recovery */
  			conf->fullsync = 1;
  	}
  
  	conf->level = mddev->new_level;
  	if (conf->level == 6) {
  		conf->max_degraded = 2;
  		if (raid6_call.xor_syndrome)
  			conf->rmw_level = PARITY_ENABLE_RMW;
  		else
  			conf->rmw_level = PARITY_DISABLE_RMW;
  	} else {
  		conf->max_degraded = 1;
  		conf->rmw_level = PARITY_ENABLE_RMW;
  	}
  	conf->algorithm = mddev->new_layout;
  	conf->reshape_progress = mddev->reshape_position;
  	if (conf->reshape_progress != MaxSector) {
  		conf->prev_chunk_sectors = mddev->chunk_sectors;
  		conf->prev_algo = mddev->layout;
  	} else {
  		conf->prev_chunk_sectors = conf->chunk_sectors;
  		conf->prev_algo = conf->algorithm;
  	}
  
  	conf->min_nr_stripes = NR_STRIPES;
  	if (mddev->reshape_position != MaxSector) {
  		int stripes = max_t(int,
  			((mddev->chunk_sectors << 9) / RAID5_STRIPE_SIZE(conf)) * 4,
  			((mddev->new_chunk_sectors << 9) / RAID5_STRIPE_SIZE(conf)) * 4);
  		conf->min_nr_stripes = max(NR_STRIPES, stripes);
  		if (conf->min_nr_stripes != NR_STRIPES)
  			pr_info("md/raid:%s: force stripe size %d for reshape\n",
  				mdname(mddev), conf->min_nr_stripes);
  	}
  	memory = conf->min_nr_stripes * (sizeof(struct stripe_head) +
  		 max_disks * ((sizeof(struct bio) + PAGE_SIZE))) / 1024;
  	atomic_set(&conf->empty_inactive_list_nr, NR_STRIPE_HASH_LOCKS);
  	if (grow_stripes(conf, conf->min_nr_stripes)) {
  		pr_warn("md/raid:%s: couldn't allocate %dkB for buffers\n",
  			mdname(mddev), memory);
  		goto abort;
  	} else
  		pr_debug("md/raid:%s: allocated %dkB\n", mdname(mddev), memory);
  	/*
  	 * Losing a stripe head costs more than the time to refill it,
  	 * it reduces the queue depth and so can hurt throughput.
  	 * So set it rather large, scaled by number of devices.
  	 */
  	conf->shrinker.seeks = DEFAULT_SEEKS * conf->raid_disks * 4;
  	conf->shrinker.scan_objects = raid5_cache_scan;
  	conf->shrinker.count_objects = raid5_cache_count;
  	conf->shrinker.batch = 128;
  	conf->shrinker.flags = 0;
  	if (register_shrinker(&conf->shrinker)) {
  		pr_warn("md/raid:%s: couldn't register shrinker.\n",
  			mdname(mddev));
  		goto abort;
  	}
  
  	sprintf(pers_name, "raid%d", mddev->new_level);
  	conf->thread = md_register_thread(raid5d, mddev, pers_name);
  	if (!conf->thread) {
  		pr_warn("md/raid:%s: couldn't allocate thread.\n",
  			mdname(mddev));
  		goto abort;
  	}
  
  	return conf;
  
   abort:
  	if (conf) {
  		free_conf(conf);
  		return ERR_PTR(-EIO);
  	} else
  		return ERR_PTR(-ENOMEM);
  }
  
  static int only_parity(int raid_disk, int algo, int raid_disks, int max_degraded)
  {
  	switch (algo) {
  	case ALGORITHM_PARITY_0:
  		if (raid_disk < max_degraded)
  			return 1;
  		break;
  	case ALGORITHM_PARITY_N:
  		if (raid_disk >= raid_disks - max_degraded)
  			return 1;
  		break;
  	case ALGORITHM_PARITY_0_6:
  		if (raid_disk == 0 ||
  		    raid_disk == raid_disks - 1)
  			return 1;
  		break;
  	case ALGORITHM_LEFT_ASYMMETRIC_6:
  	case ALGORITHM_RIGHT_ASYMMETRIC_6:
  	case ALGORITHM_LEFT_SYMMETRIC_6:
  	case ALGORITHM_RIGHT_SYMMETRIC_6:
  		if (raid_disk == raid_disks - 1)
  			return 1;
  	}
  	return 0;
  }
  
  static void raid5_set_io_opt(struct r5conf *conf)
  {
  	blk_queue_io_opt(conf->mddev->queue, (conf->chunk_sectors << 9) *
  			 (conf->raid_disks - conf->max_degraded));
  }
  
  static int raid5_run(struct mddev *mddev)
  {
  	struct r5conf *conf;
  	int working_disks = 0;
  	int dirty_parity_disks = 0;
  	struct md_rdev *rdev;
  	struct md_rdev *journal_dev = NULL;
  	sector_t reshape_offset = 0;
  	int i;
  	long long min_offset_diff = 0;
  	int first = 1;
  
  	if (mddev_init_writes_pending(mddev) < 0)
  		return -ENOMEM;
  
  	if (mddev->recovery_cp != MaxSector)
  		pr_notice("md/raid:%s: not clean -- starting background reconstruction\n",
  			  mdname(mddev));
  
  	rdev_for_each(rdev, mddev) {
  		long long diff;
  
  		if (test_bit(Journal, &rdev->flags)) {
  			journal_dev = rdev;
  			continue;
  		}
  		if (rdev->raid_disk < 0)
  			continue;
  		diff = (rdev->new_data_offset - rdev->data_offset);
  		if (first) {
  			min_offset_diff = diff;
  			first = 0;
  		} else if (mddev->reshape_backwards &&
  			 diff < min_offset_diff)
  			min_offset_diff = diff;
  		else if (!mddev->reshape_backwards &&
  			 diff > min_offset_diff)
  			min_offset_diff = diff;
  	}
  
  	if ((test_bit(MD_HAS_JOURNAL, &mddev->flags) || journal_dev) &&
  	    (mddev->bitmap_info.offset || mddev->bitmap_info.file)) {
  		pr_notice("md/raid:%s: array cannot have both journal and bitmap\n",
  			  mdname(mddev));
  		return -EINVAL;
  	}
  
  	if (mddev->reshape_position != MaxSector) {
  		/* Check that we can continue the reshape.
  		 * Difficulties arise if the stripe we would write to
  		 * next is at or after the stripe we would read from next.
  		 * For a reshape that changes the number of devices, this
  		 * is only possible for a very short time, and mdadm makes
  		 * sure that time appears to have past before assembling
  		 * the array.  So we fail if that time hasn't passed.
  		 * For a reshape that keeps the number of devices the same
  		 * mdadm must be monitoring the reshape can keeping the
  		 * critical areas read-only and backed up.  It will start
  		 * the array in read-only mode, so we check for that.
  		 */
  		sector_t here_new, here_old;
  		int old_disks;
  		int max_degraded = (mddev->level == 6 ? 2 : 1);
  		int chunk_sectors;
  		int new_data_disks;
  
  		if (journal_dev) {
  			pr_warn("md/raid:%s: don't support reshape with journal - aborting.\n",
  				mdname(mddev));
  			return -EINVAL;
  		}
  
  		if (mddev->new_level != mddev->level) {
  			pr_warn("md/raid:%s: unsupported reshape required - aborting.\n",
  				mdname(mddev));
  			return -EINVAL;
  		}
  		old_disks = mddev->raid_disks - mddev->delta_disks;
  		/* reshape_position must be on a new-stripe boundary, and one
  		 * further up in new geometry must map after here in old
  		 * geometry.
  		 * If the chunk sizes are different, then as we perform reshape
  		 * in units of the largest of the two, reshape_position needs
  		 * be a multiple of the largest chunk size times new data disks.
  		 */
  		here_new = mddev->reshape_position;
  		chunk_sectors = max(mddev->chunk_sectors, mddev->new_chunk_sectors);
  		new_data_disks = mddev->raid_disks - max_degraded;
  		if (sector_div(here_new, chunk_sectors * new_data_disks)) {
  			pr_warn("md/raid:%s: reshape_position not on a stripe boundary\n",
  				mdname(mddev));
  			return -EINVAL;
  		}
  		reshape_offset = here_new * chunk_sectors;
  		/* here_new is the stripe we will write to */
  		here_old = mddev->reshape_position;
  		sector_div(here_old, chunk_sectors * (old_disks-max_degraded));
  		/* here_old is the first stripe that we might need to read
  		 * from */
  		if (mddev->delta_disks == 0) {
  			/* We cannot be sure it is safe to start an in-place
  			 * reshape.  It is only safe if user-space is monitoring
  			 * and taking constant backups.
  			 * mdadm always starts a situation like this in
  			 * readonly mode so it can take control before
  			 * allowing any writes.  So just check for that.
  			 */
  			if (abs(min_offset_diff) >= mddev->chunk_sectors &&
  			    abs(min_offset_diff) >= mddev->new_chunk_sectors)
  				/* not really in-place - so OK */;
  			else if (mddev->ro == 0) {
  				pr_warn("md/raid:%s: in-place reshape must be started in read-only mode - aborting\n",
  					mdname(mddev));
  				return -EINVAL;
  			}
  		} else if (mddev->reshape_backwards
  		    ? (here_new * chunk_sectors + min_offset_diff <=
  		       here_old * chunk_sectors)
  		    : (here_new * chunk_sectors >=
  		       here_old * chunk_sectors + (-min_offset_diff))) {
  			/* Reading from the same stripe as writing to - bad */
  			pr_warn("md/raid:%s: reshape_position too early for auto-recovery - aborting.\n",
  				mdname(mddev));
  			return -EINVAL;
  		}
  		pr_debug("md/raid:%s: reshape will continue\n", mdname(mddev));
  		/* OK, we should be able to continue; */
  	} else {
  		BUG_ON(mddev->level != mddev->new_level);
  		BUG_ON(mddev->layout != mddev->new_layout);
  		BUG_ON(mddev->chunk_sectors != mddev->new_chunk_sectors);
  		BUG_ON(mddev->delta_disks != 0);
  	}
  
  	if (test_bit(MD_HAS_JOURNAL, &mddev->flags) &&
  	    test_bit(MD_HAS_PPL, &mddev->flags)) {
  		pr_warn("md/raid:%s: using journal device and PPL not allowed - disabling PPL\n",
  			mdname(mddev));
  		clear_bit(MD_HAS_PPL, &mddev->flags);
  		clear_bit(MD_HAS_MULTIPLE_PPLS, &mddev->flags);
  	}
  
  	if (mddev->private == NULL)
  		conf = setup_conf(mddev);
  	else
  		conf = mddev->private;
  
  	if (IS_ERR(conf))
  		return PTR_ERR(conf);
  
  	if (test_bit(MD_HAS_JOURNAL, &mddev->flags)) {
  		if (!journal_dev) {
  			pr_warn("md/raid:%s: journal disk is missing, force array readonly\n",
  				mdname(mddev));
  			mddev->ro = 1;
  			set_disk_ro(mddev->gendisk, 1);
  		} else if (mddev->recovery_cp == MaxSector)
  			set_bit(MD_JOURNAL_CLEAN, &mddev->flags);
  	}
  
  	conf->min_offset_diff = min_offset_diff;
  	mddev->thread = conf->thread;
  	conf->thread = NULL;
  	mddev->private = conf;
  
  	for (i = 0; i < conf->raid_disks && conf->previous_raid_disks;
  	     i++) {
  		rdev = conf->disks[i].rdev;
  		if (!rdev && conf->disks[i].replacement) {
  			/* The replacement is all we have yet */
  			rdev = conf->disks[i].replacement;
  			conf->disks[i].replacement = NULL;
  			clear_bit(Replacement, &rdev->flags);
  			conf->disks[i].rdev = rdev;
  		}
  		if (!rdev)
  			continue;
  		if (conf->disks[i].replacement &&
  		    conf->reshape_progress != MaxSector) {
  			/* replacements and reshape simply do not mix. */
  			pr_warn("md: cannot handle concurrent replacement and reshape.\n");
  			goto abort;
  		}
  		if (test_bit(In_sync, &rdev->flags)) {
  			working_disks++;
  			continue;
  		}
  		/* This disc is not fully in-sync.  However if it
  		 * just stored parity (beyond the recovery_offset),
  		 * when we don't need to be concerned about the
  		 * array being dirty.
  		 * When reshape goes 'backwards', we never have
  		 * partially completed devices, so we only need
  		 * to worry about reshape going forwards.
  		 */
  		/* Hack because v0.91 doesn't store recovery_offset properly. */
  		if (mddev->major_version == 0 &&
  		    mddev->minor_version > 90)
  			rdev->recovery_offset = reshape_offset;
  
  		if (rdev->recovery_offset < reshape_offset) {
  			/* We need to check old and new layout */
  			if (!only_parity(rdev->raid_disk,
  					 conf->algorithm,
  					 conf->raid_disks,
  					 conf->max_degraded))
  				continue;
  		}
  		if (!only_parity(rdev->raid_disk,
  				 conf->prev_algo,
  				 conf->previous_raid_disks,
  				 conf->max_degraded))
  			continue;
  		dirty_parity_disks++;
  	}
  
  	/*
  	 * 0 for a fully functional array, 1 or 2 for a degraded array.
  	 */
  	mddev->degraded = raid5_calc_degraded(conf);
  
  	if (has_failed(conf)) {
  		pr_crit("md/raid:%s: not enough operational devices (%d/%d failed)\n",
  			mdname(mddev), mddev->degraded, conf->raid_disks);
  		goto abort;
  	}
  
  	/* device size must be a multiple of chunk size */
  	mddev->dev_sectors &= ~(mddev->chunk_sectors - 1);
  	mddev->resync_max_sectors = mddev->dev_sectors;
  
  	if (mddev->degraded > dirty_parity_disks &&
  	    mddev->recovery_cp != MaxSector) {
  		if (test_bit(MD_HAS_PPL, &mddev->flags))
  			pr_crit("md/raid:%s: starting dirty degraded array with PPL.\n",
  				mdname(mddev));
  		else if (mddev->ok_start_degraded)
  			pr_crit("md/raid:%s: starting dirty degraded array - data corruption possible.\n",
  				mdname(mddev));
  		else {
  			pr_crit("md/raid:%s: cannot start dirty degraded array.\n",
  				mdname(mddev));
  			goto abort;
  		}
  	}
  
  	pr_info("md/raid:%s: raid level %d active with %d out of %d devices, algorithm %d\n",
  		mdname(mddev), conf->level,
  		mddev->raid_disks-mddev->degraded, mddev->raid_disks,
  		mddev->new_layout);
  
  	print_raid5_conf(conf);
  
  	if (conf->reshape_progress != MaxSector) {
  		conf->reshape_safe = conf->reshape_progress;
  		atomic_set(&conf->reshape_stripes, 0);
  		clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
  		clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
  		set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
  		set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
  		mddev->sync_thread = md_register_thread(md_do_sync, mddev,
  							"reshape");
  		if (!mddev->sync_thread)
  			goto abort;
  	}
  
  	/* Ok, everything is just fine now */
  	if (mddev->to_remove == &raid5_attrs_group)
  		mddev->to_remove = NULL;
  	else if (mddev->kobj.sd &&
  	    sysfs_create_group(&mddev->kobj, &raid5_attrs_group))
  		pr_warn("raid5: failed to create sysfs attributes for %s\n",
  			mdname(mddev));
  	md_set_array_sectors(mddev, raid5_size(mddev, 0, 0));
  
  	if (mddev->queue) {
  		int chunk_size;
  		/* read-ahead size must cover two whole stripes, which
  		 * is 2 * (datadisks) * chunksize where 'n' is the
  		 * number of raid devices
  		 */
  		int data_disks = conf->previous_raid_disks - conf->max_degraded;
  		int stripe = data_disks *
  			((mddev->chunk_sectors << 9) / PAGE_SIZE);
  
  		chunk_size = mddev->chunk_sectors << 9;
  		blk_queue_io_min(mddev->queue, chunk_size);
  		raid5_set_io_opt(conf);
  		mddev->queue->limits.raid_partial_stripes_expensive = 1;
  		/*
  		 * We can only discard a whole stripe. It doesn't make sense to
  		 * discard data disk but write parity disk
  		 */
  		stripe = stripe * PAGE_SIZE;
  		/* Round up to power of 2, as discard handling
  		 * currently assumes that */
  		while ((stripe-1) & stripe)
  			stripe = (stripe | (stripe-1)) + 1;
  		mddev->queue->limits.discard_alignment = stripe;
  		mddev->queue->limits.discard_granularity = stripe;
  
  		blk_queue_max_write_same_sectors(mddev->queue, 0);
  		blk_queue_max_write_zeroes_sectors(mddev->queue, 0);
  
  		rdev_for_each(rdev, mddev) {
  			disk_stack_limits(mddev->gendisk, rdev->bdev,
  					  rdev->data_offset << 9);
  			disk_stack_limits(mddev->gendisk, rdev->bdev,
  					  rdev->new_data_offset << 9);
  		}
  
  		/*
  		 * zeroing is required, otherwise data
  		 * could be lost. Consider a scenario: discard a stripe
  		 * (the stripe could be inconsistent if
  		 * discard_zeroes_data is 0); write one disk of the
  		 * stripe (the stripe could be inconsistent again
  		 * depending on which disks are used to calculate
  		 * parity); the disk is broken; The stripe data of this
  		 * disk is lost.
  		 *
  		 * We only allow DISCARD if the sysadmin has confirmed that
  		 * only safe devices are in use by setting a module parameter.
  		 * A better idea might be to turn DISCARD into WRITE_ZEROES
  		 * requests, as that is required to be safe.
  		 */
  		if (devices_handle_discard_safely &&
  		    mddev->queue->limits.max_discard_sectors >= (stripe >> 9) &&
  		    mddev->queue->limits.discard_granularity >= stripe)
  			blk_queue_flag_set(QUEUE_FLAG_DISCARD,
  						mddev->queue);
  		else
  			blk_queue_flag_clear(QUEUE_FLAG_DISCARD,
  						mddev->queue);
  
  		blk_queue_max_hw_sectors(mddev->queue, UINT_MAX);
  	}
  
  	if (log_init(conf, journal_dev, raid5_has_ppl(conf)))
  		goto abort;
  
  	return 0;
  abort:
  	md_unregister_thread(&mddev->thread);
  	print_raid5_conf(conf);
  	free_conf(conf);
  	mddev->private = NULL;
  	pr_warn("md/raid:%s: failed to run raid set.\n", mdname(mddev));
  	return -EIO;
  }
  
  static void raid5_free(struct mddev *mddev, void *priv)
  {
  	struct r5conf *conf = priv;
  
  	free_conf(conf);
  	mddev->to_remove = &raid5_attrs_group;
  }
  
  static void raid5_status(struct seq_file *seq, struct mddev *mddev)
  {
  	struct r5conf *conf = mddev->private;
  	int i;
  
  	seq_printf(seq, " level %d, %dk chunk, algorithm %d", mddev->level,
  		conf->chunk_sectors / 2, mddev->layout);
  	seq_printf (seq, " [%d/%d] [", conf->raid_disks, conf->raid_disks - mddev->degraded);
  	rcu_read_lock();
  	for (i = 0; i < conf->raid_disks; i++) {
  		struct md_rdev *rdev = rcu_dereference(conf->disks[i].rdev);
  		seq_printf (seq, "%s", rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");
  	}
  	rcu_read_unlock();
  	seq_printf (seq, "]");
  }
  
  static void print_raid5_conf (struct r5conf *conf)
  {
  	int i;
  	struct disk_info *tmp;
  
  	pr_debug("RAID conf printout:\n");
  	if (!conf) {
  		pr_debug("(conf==NULL)\n");
  		return;
  	}
  	pr_debug(" --- level:%d rd:%d wd:%d\n", conf->level,
  	       conf->raid_disks,
  	       conf->raid_disks - conf->mddev->degraded);
  
  	for (i = 0; i < conf->raid_disks; i++) {
  		char b[BDEVNAME_SIZE];
  		tmp = conf->disks + i;
  		if (tmp->rdev)
  			pr_debug(" disk %d, o:%d, dev:%s\n",
  			       i, !test_bit(Faulty, &tmp->rdev->flags),
  			       bdevname(tmp->rdev->bdev, b));
  	}
  }
  
  static int raid5_spare_active(struct mddev *mddev)
  {
  	int i;
  	struct r5conf *conf = mddev->private;
  	struct disk_info *tmp;
  	int count = 0;
  	unsigned long flags;
  
  	for (i = 0; i < conf->raid_disks; i++) {
  		tmp = conf->disks + i;
  		if (tmp->replacement
  		    && tmp->replacement->recovery_offset == MaxSector
  		    && !test_bit(Faulty, &tmp->replacement->flags)
  		    && !test_and_set_bit(In_sync, &tmp->replacement->flags)) {
  			/* Replacement has just become active. */
  			if (!tmp->rdev
  			    || !test_and_clear_bit(In_sync, &tmp->rdev->flags))
  				count++;
  			if (tmp->rdev) {
  				/* Replaced device not technically faulty,
  				 * but we need to be sure it gets removed
  				 * and never re-added.
  				 */
  				set_bit(Faulty, &tmp->rdev->flags);
  				sysfs_notify_dirent_safe(
  					tmp->rdev->sysfs_state);
  			}
  			sysfs_notify_dirent_safe(tmp->replacement->sysfs_state);
  		} else if (tmp->rdev
  		    && tmp->rdev->recovery_offset == MaxSector
  		    && !test_bit(Faulty, &tmp->rdev->flags)
  		    && !test_and_set_bit(In_sync, &tmp->rdev->flags)) {
  			count++;
  			sysfs_notify_dirent_safe(tmp->rdev->sysfs_state);
  		}
  	}
  	spin_lock_irqsave(&conf->device_lock, flags);
  	mddev->degraded = raid5_calc_degraded(conf);
  	spin_unlock_irqrestore(&conf->device_lock, flags);
  	print_raid5_conf(conf);
  	return count;
  }
  
  static int raid5_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
  {
  	struct r5conf *conf = mddev->private;
  	int err = 0;
  	int number = rdev->raid_disk;
  	struct md_rdev **rdevp;
  	struct disk_info *p = conf->disks + number;
  
  	print_raid5_conf(conf);
  	if (test_bit(Journal, &rdev->flags) && conf->log) {
  		/*
  		 * we can't wait pending write here, as this is called in
  		 * raid5d, wait will deadlock.
  		 * neilb: there is no locking about new writes here,
  		 * so this cannot be safe.
  		 */
  		if (atomic_read(&conf->active_stripes) ||
  		    atomic_read(&conf->r5c_cached_full_stripes) ||
  		    atomic_read(&conf->r5c_cached_partial_stripes)) {
  			return -EBUSY;
  		}
  		log_exit(conf);
  		return 0;
  	}
  	if (rdev == p->rdev)
  		rdevp = &p->rdev;
  	else if (rdev == p->replacement)
  		rdevp = &p->replacement;
  	else
  		return 0;
  
  	if (number >= conf->raid_disks &&
  	    conf->reshape_progress == MaxSector)
  		clear_bit(In_sync, &rdev->flags);
  
  	if (test_bit(In_sync, &rdev->flags) ||
  	    atomic_read(&rdev->nr_pending)) {
  		err = -EBUSY;
  		goto abort;
  	}
  	/* Only remove non-faulty devices if recovery
  	 * isn't possible.
  	 */
  	if (!test_bit(Faulty, &rdev->flags) &&
  	    mddev->recovery_disabled != conf->recovery_disabled &&
  	    !has_failed(conf) &&
  	    (!p->replacement || p->replacement == rdev) &&
  	    number < conf->raid_disks) {
  		err = -EBUSY;
  		goto abort;
  	}
  	*rdevp = NULL;
  	if (!test_bit(RemoveSynchronized, &rdev->flags)) {
  		synchronize_rcu();
  		if (atomic_read(&rdev->nr_pending)) {
  			/* lost the race, try later */
  			err = -EBUSY;
  			*rdevp = rdev;
  		}
  	}
  	if (!err) {
  		err = log_modify(conf, rdev, false);
  		if (err)
  			goto abort;
  	}
  	if (p->replacement) {
  		/* We must have just cleared 'rdev' */
  		p->rdev = p->replacement;
  		clear_bit(Replacement, &p->replacement->flags);
  		smp_mb(); /* Make sure other CPUs may see both as identical
  			   * but will never see neither - if they are careful
  			   */
  		p->replacement = NULL;
  
  		if (!err)
  			err = log_modify(conf, p->rdev, true);
  	}
  
  	clear_bit(WantReplacement, &rdev->flags);
  abort:
  
  	print_raid5_conf(conf);
  	return err;
  }
  
  static int raid5_add_disk(struct mddev *mddev, struct md_rdev *rdev)
  {
  	struct r5conf *conf = mddev->private;
  	int ret, err = -EEXIST;
  	int disk;
  	struct disk_info *p;
  	int first = 0;
  	int last = conf->raid_disks - 1;
  
  	if (test_bit(Journal, &rdev->flags)) {
  		if (conf->log)
  			return -EBUSY;
  
  		rdev->raid_disk = 0;
  		/*
  		 * The array is in readonly mode if journal is missing, so no
  		 * write requests running. We should be safe
  		 */
  		ret = log_init(conf, rdev, false);
  		if (ret)
  			return ret;
  
  		ret = r5l_start(conf->log);
  		if (ret)
  			return ret;
  
  		return 0;
  	}
  	if (mddev->recovery_disabled == conf->recovery_disabled)
  		return -EBUSY;
  
  	if (rdev->saved_raid_disk < 0 && has_failed(conf))
  		/* no point adding a device */
  		return -EINVAL;
  
  	if (rdev->raid_disk >= 0)
  		first = last = rdev->raid_disk;
  
  	/*
  	 * find the disk ... but prefer rdev->saved_raid_disk
  	 * if possible.
  	 */
  	if (rdev->saved_raid_disk >= 0 &&
  	    rdev->saved_raid_disk >= first &&
  	    conf->disks[rdev->saved_raid_disk].rdev == NULL)
  		first = rdev->saved_raid_disk;
  
  	for (disk = first; disk <= last; disk++) {
  		p = conf->disks + disk;
  		if (p->rdev == NULL) {
  			clear_bit(In_sync, &rdev->flags);
  			rdev->raid_disk = disk;
  			if (rdev->saved_raid_disk != disk)
  				conf->fullsync = 1;
  			rcu_assign_pointer(p->rdev, rdev);
  
  			err = log_modify(conf, rdev, true);
  
  			goto out;
  		}
  	}
  	for (disk = first; disk <= last; disk++) {
  		p = conf->disks + disk;
  		if (test_bit(WantReplacement, &p->rdev->flags) &&
  		    p->replacement == NULL) {
  			clear_bit(In_sync, &rdev->flags);
  			set_bit(Replacement, &rdev->flags);
  			rdev->raid_disk = disk;
  			err = 0;
  			conf->fullsync = 1;
  			rcu_assign_pointer(p->replacement, rdev);
  			break;
  		}
  	}
  out:
  	print_raid5_conf(conf);
  	return err;
  }
  
  static int raid5_resize(struct mddev *mddev, sector_t sectors)
  {
  	/* no resync is happening, and there is enough space
  	 * on all devices, so we can resize.
  	 * We need to make sure resync covers any new space.
  	 * If the array is shrinking we should possibly wait until
  	 * any io in the removed space completes, but it hardly seems
  	 * worth it.
  	 */
  	sector_t newsize;
  	struct r5conf *conf = mddev->private;
  
  	if (raid5_has_log(conf) || raid5_has_ppl(conf))
  		return -EINVAL;
  	sectors &= ~((sector_t)conf->chunk_sectors - 1);
  	newsize = raid5_size(mddev, sectors, mddev->raid_disks);
  	if (mddev->external_size &&
  	    mddev->array_sectors > newsize)
  		return -EINVAL;
  	if (mddev->bitmap) {
  		int ret = md_bitmap_resize(mddev->bitmap, sectors, 0, 0);
  		if (ret)
  			return ret;
  	}
  	md_set_array_sectors(mddev, newsize);
  	if (sectors > mddev->dev_sectors &&
  	    mddev->recovery_cp > mddev->dev_sectors) {
  		mddev->recovery_cp = mddev->dev_sectors;
  		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
  	}
  	mddev->dev_sectors = sectors;
  	mddev->resync_max_sectors = sectors;
  	return 0;
  }
  
  static int check_stripe_cache(struct mddev *mddev)
  {
  	/* Can only proceed if there are plenty of stripe_heads.
  	 * We need a minimum of one full stripe,, and for sensible progress
  	 * it is best to have about 4 times that.
  	 * If we require 4 times, then the default 256 4K stripe_heads will
  	 * allow for chunk sizes up to 256K, which is probably OK.
  	 * If the chunk size is greater, user-space should request more
  	 * stripe_heads first.
  	 */
  	struct r5conf *conf = mddev->private;
  	if (((mddev->chunk_sectors << 9) / RAID5_STRIPE_SIZE(conf)) * 4
  	    > conf->min_nr_stripes ||
  	    ((mddev->new_chunk_sectors << 9) / RAID5_STRIPE_SIZE(conf)) * 4
  	    > conf->min_nr_stripes) {
  		pr_warn("md/raid:%s: reshape: not enough stripes.  Needed %lu\n",
  			mdname(mddev),
  			((max(mddev->chunk_sectors, mddev->new_chunk_sectors) << 9)
  			 / RAID5_STRIPE_SIZE(conf))*4);
  		return 0;
  	}
  	return 1;
  }
  
  static int check_reshape(struct mddev *mddev)
  {
  	struct r5conf *conf = mddev->private;
  
  	if (raid5_has_log(conf) || raid5_has_ppl(conf))
  		return -EINVAL;
  	if (mddev->delta_disks == 0 &&
  	    mddev->new_layout == mddev->layout &&
  	    mddev->new_chunk_sectors == mddev->chunk_sectors)
  		return 0; /* nothing to do */
  	if (has_failed(conf))
  		return -EINVAL;
  	if (mddev->delta_disks < 0 && mddev->reshape_position == MaxSector) {
  		/* We might be able to shrink, but the devices must
  		 * be made bigger first.
  		 * For raid6, 4 is the minimum size.
  		 * Otherwise 2 is the minimum
  		 */
  		int min = 2;
  		if (mddev->level == 6)
  			min = 4;
  		if (mddev->raid_disks + mddev->delta_disks < min)
  			return -EINVAL;
  	}
  
  	if (!check_stripe_cache(mddev))
  		return -ENOSPC;
  
  	if (mddev->new_chunk_sectors > mddev->chunk_sectors ||
  	    mddev->delta_disks > 0)
  		if (resize_chunks(conf,
  				  conf->previous_raid_disks
  				  + max(0, mddev->delta_disks),
  				  max(mddev->new_chunk_sectors,
  				      mddev->chunk_sectors)
  			    ) < 0)
  			return -ENOMEM;
  
  	if (conf->previous_raid_disks + mddev->delta_disks <= conf->pool_size)
  		return 0; /* never bother to shrink */
  	return resize_stripes(conf, (conf->previous_raid_disks
  				     + mddev->delta_disks));
  }
  
  static int raid5_start_reshape(struct mddev *mddev)
  {
  	struct r5conf *conf = mddev->private;
  	struct md_rdev *rdev;
  	int spares = 0;
  	unsigned long flags;
  
  	if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
  		return -EBUSY;
  
  	if (!check_stripe_cache(mddev))
  		return -ENOSPC;
  
  	if (has_failed(conf))
  		return -EINVAL;
  
  	rdev_for_each(rdev, mddev) {
  		if (!test_bit(In_sync, &rdev->flags)
  		    && !test_bit(Faulty, &rdev->flags))
  			spares++;
  	}
  
  	if (spares - mddev->degraded < mddev->delta_disks - conf->max_degraded)
  		/* Not enough devices even to make a degraded array
  		 * of that size
  		 */
  		return -EINVAL;
  
  	/* Refuse to reduce size of the array.  Any reductions in
  	 * array size must be through explicit setting of array_size
  	 * attribute.
  	 */
  	if (raid5_size(mddev, 0, conf->raid_disks + mddev->delta_disks)
  	    < mddev->array_sectors) {
  		pr_warn("md/raid:%s: array size must be reduced before number of disks\n",
  			mdname(mddev));
  		return -EINVAL;
  	}
  
  	atomic_set(&conf->reshape_stripes, 0);
  	spin_lock_irq(&conf->device_lock);
  	write_seqcount_begin(&conf->gen_lock);
  	conf->previous_raid_disks = conf->raid_disks;
  	conf->raid_disks += mddev->delta_disks;
  	conf->prev_chunk_sectors = conf->chunk_sectors;
  	conf->chunk_sectors = mddev->new_chunk_sectors;
  	conf->prev_algo = conf->algorithm;
  	conf->algorithm = mddev->new_layout;
  	conf->generation++;
  	/* Code that selects data_offset needs to see the generation update
  	 * if reshape_progress has been set - so a memory barrier needed.
  	 */
  	smp_mb();
  	if (mddev->reshape_backwards)
  		conf->reshape_progress = raid5_size(mddev, 0, 0);
  	else
  		conf->reshape_progress = 0;
  	conf->reshape_safe = conf->reshape_progress;
  	write_seqcount_end(&conf->gen_lock);
  	spin_unlock_irq(&conf->device_lock);
  
  	/* Now make sure any requests that proceeded on the assumption
  	 * the reshape wasn't running - like Discard or Read - have
  	 * completed.
  	 */
  	mddev_suspend(mddev);
  	mddev_resume(mddev);
  
  	/* Add some new drives, as many as will fit.
  	 * We know there are enough to make the newly sized array work.
  	 * Don't add devices if we are reducing the number of
  	 * devices in the array.  This is because it is not possible
  	 * to correctly record the "partially reconstructed" state of
  	 * such devices during the reshape and confusion could result.
  	 */
  	if (mddev->delta_disks >= 0) {
  		rdev_for_each(rdev, mddev)
  			if (rdev->raid_disk < 0 &&
  			    !test_bit(Faulty, &rdev->flags)) {
  				if (raid5_add_disk(mddev, rdev) == 0) {
  					if (rdev->raid_disk
  					    >= conf->previous_raid_disks)
  						set_bit(In_sync, &rdev->flags);
  					else
  						rdev->recovery_offset = 0;
  
  					/* Failure here is OK */
  					sysfs_link_rdev(mddev, rdev);
  				}
  			} else if (rdev->raid_disk >= conf->previous_raid_disks
  				   && !test_bit(Faulty, &rdev->flags)) {
  				/* This is a spare that was manually added */
  				set_bit(In_sync, &rdev->flags);
  			}
  
  		/* When a reshape changes the number of devices,
  		 * ->degraded is measured against the larger of the
  		 * pre and post number of devices.
  		 */
  		spin_lock_irqsave(&conf->device_lock, flags);
  		mddev->degraded = raid5_calc_degraded(conf);
  		spin_unlock_irqrestore(&conf->device_lock, flags);
  	}
  	mddev->raid_disks = conf->raid_disks;
  	mddev->reshape_position = conf->reshape_progress;
  	set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
  
  	clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
  	clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
  	clear_bit(MD_RECOVERY_DONE, &mddev->recovery);
  	set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
  	set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
  	mddev->sync_thread = md_register_thread(md_do_sync, mddev,
  						"reshape");
  	if (!mddev->sync_thread) {
  		mddev->recovery = 0;
  		spin_lock_irq(&conf->device_lock);
  		write_seqcount_begin(&conf->gen_lock);
  		mddev->raid_disks = conf->raid_disks = conf->previous_raid_disks;
  		mddev->new_chunk_sectors =
  			conf->chunk_sectors = conf->prev_chunk_sectors;
  		mddev->new_layout = conf->algorithm = conf->prev_algo;
  		rdev_for_each(rdev, mddev)
  			rdev->new_data_offset = rdev->data_offset;
  		smp_wmb();
  		conf->generation --;
  		conf->reshape_progress = MaxSector;
  		mddev->reshape_position = MaxSector;
  		write_seqcount_end(&conf->gen_lock);
  		spin_unlock_irq(&conf->device_lock);
  		return -EAGAIN;
  	}
  	conf->reshape_checkpoint = jiffies;
  	md_wakeup_thread(mddev->sync_thread);
  	md_new_event(mddev);
  	return 0;
  }
  
  /* This is called from the reshape thread and should make any
   * changes needed in 'conf'
   */
  static void end_reshape(struct r5conf *conf)
  {
  
  	if (!test_bit(MD_RECOVERY_INTR, &conf->mddev->recovery)) {
  		struct md_rdev *rdev;
  
  		spin_lock_irq(&conf->device_lock);
  		conf->previous_raid_disks = conf->raid_disks;
  		md_finish_reshape(conf->mddev);
  		smp_wmb();
  		conf->reshape_progress = MaxSector;
  		conf->mddev->reshape_position = MaxSector;
  		rdev_for_each(rdev, conf->mddev)
  			if (rdev->raid_disk >= 0 &&
  			    !test_bit(Journal, &rdev->flags) &&
  			    !test_bit(In_sync, &rdev->flags))
  				rdev->recovery_offset = MaxSector;
  		spin_unlock_irq(&conf->device_lock);
  		wake_up(&conf->wait_for_overlap);
  
  		if (conf->mddev->queue)
  			raid5_set_io_opt(conf);
  	}
  }
  
  /* This is called from the raid5d thread with mddev_lock held.
   * It makes config changes to the device.
   */
  static void raid5_finish_reshape(struct mddev *mddev)
  {
  	struct r5conf *conf = mddev->private;
  
  	if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery)) {
  
  		if (mddev->delta_disks <= 0) {
  			int d;
  			spin_lock_irq(&conf->device_lock);
  			mddev->degraded = raid5_calc_degraded(conf);
  			spin_unlock_irq(&conf->device_lock);
  			for (d = conf->raid_disks ;
  			     d < conf->raid_disks - mddev->delta_disks;
  			     d++) {
  				struct md_rdev *rdev = conf->disks[d].rdev;
  				if (rdev)
  					clear_bit(In_sync, &rdev->flags);
  				rdev = conf->disks[d].replacement;
  				if (rdev)
  					clear_bit(In_sync, &rdev->flags);
  			}
  		}
  		mddev->layout = conf->algorithm;
  		mddev->chunk_sectors = conf->chunk_sectors;
  		mddev->reshape_position = MaxSector;
  		mddev->delta_disks = 0;
  		mddev->reshape_backwards = 0;
  	}
  }
  
  static void raid5_quiesce(struct mddev *mddev, int quiesce)
  {
  	struct r5conf *conf = mddev->private;
  
  	if (quiesce) {
  		/* stop all writes */
  		lock_all_device_hash_locks_irq(conf);
  		/* '2' tells resync/reshape to pause so that all
  		 * active stripes can drain
  		 */
  		r5c_flush_cache(conf, INT_MAX);
  		conf->quiesce = 2;
  		wait_event_cmd(conf->wait_for_quiescent,
  				    atomic_read(&conf->active_stripes) == 0 &&
  				    atomic_read(&conf->active_aligned_reads) == 0,
  				    unlock_all_device_hash_locks_irq(conf),
  				    lock_all_device_hash_locks_irq(conf));
  		conf->quiesce = 1;
  		unlock_all_device_hash_locks_irq(conf);
  		/* allow reshape to continue */
  		wake_up(&conf->wait_for_overlap);
  	} else {
  		/* re-enable writes */
  		lock_all_device_hash_locks_irq(conf);
  		conf->quiesce = 0;
  		wake_up(&conf->wait_for_quiescent);
  		wake_up(&conf->wait_for_overlap);
  		unlock_all_device_hash_locks_irq(conf);
  	}
  	log_quiesce(conf, quiesce);
  }
  
  static void *raid45_takeover_raid0(struct mddev *mddev, int level)
  {
  	struct r0conf *raid0_conf = mddev->private;
  	sector_t sectors;
  
  	/* for raid0 takeover only one zone is supported */
  	if (raid0_conf->nr_strip_zones > 1) {
  		pr_warn("md/raid:%s: cannot takeover raid0 with more than one zone.\n",
  			mdname(mddev));
  		return ERR_PTR(-EINVAL);
  	}
  
  	sectors = raid0_conf->strip_zone[0].zone_end;
  	sector_div(sectors, raid0_conf->strip_zone[0].nb_dev);
  	mddev->dev_sectors = sectors;
  	mddev->new_level = level;
  	mddev->new_layout = ALGORITHM_PARITY_N;
  	mddev->new_chunk_sectors = mddev->chunk_sectors;
  	mddev->raid_disks += 1;
  	mddev->delta_disks = 1;
  	/* make sure it will be not marked as dirty */
  	mddev->recovery_cp = MaxSector;
  
  	return setup_conf(mddev);
  }
  
  static void *raid5_takeover_raid1(struct mddev *mddev)
  {
  	int chunksect;
  	void *ret;
  
  	if (mddev->raid_disks != 2 ||
  	    mddev->degraded > 1)
  		return ERR_PTR(-EINVAL);
  
  	/* Should check if there are write-behind devices? */
  
  	chunksect = 64*2; /* 64K by default */
  
  	/* The array must be an exact multiple of chunksize */
  	while (chunksect && (mddev->array_sectors & (chunksect-1)))
  		chunksect >>= 1;
  
  	if ((chunksect<<9) < RAID5_STRIPE_SIZE((struct r5conf *)mddev->private))
  		/* array size does not allow a suitable chunk size */
  		return ERR_PTR(-EINVAL);
  
  	mddev->new_level = 5;
  	mddev->new_layout = ALGORITHM_LEFT_SYMMETRIC;
  	mddev->new_chunk_sectors = chunksect;
  
  	ret = setup_conf(mddev);
  	if (!IS_ERR(ret))
  		mddev_clear_unsupported_flags(mddev,
  			UNSUPPORTED_MDDEV_FLAGS);
  	return ret;
  }
  
  static void *raid5_takeover_raid6(struct mddev *mddev)
  {
  	int new_layout;
  
  	switch (mddev->layout) {
  	case ALGORITHM_LEFT_ASYMMETRIC_6:
  		new_layout = ALGORITHM_LEFT_ASYMMETRIC;
  		break;
  	case ALGORITHM_RIGHT_ASYMMETRIC_6:
  		new_layout = ALGORITHM_RIGHT_ASYMMETRIC;
  		break;
  	case ALGORITHM_LEFT_SYMMETRIC_6:
  		new_layout = ALGORITHM_LEFT_SYMMETRIC;
  		break;
  	case ALGORITHM_RIGHT_SYMMETRIC_6:
  		new_layout = ALGORITHM_RIGHT_SYMMETRIC;
  		break;
  	case ALGORITHM_PARITY_0_6:
  		new_layout = ALGORITHM_PARITY_0;
  		break;
  	case ALGORITHM_PARITY_N:
  		new_layout = ALGORITHM_PARITY_N;
  		break;
  	default:
  		return ERR_PTR(-EINVAL);
  	}
  	mddev->new_level = 5;
  	mddev->new_layout = new_layout;
  	mddev->delta_disks = -1;
  	mddev->raid_disks -= 1;
  	return setup_conf(mddev);
  }
  
  static int raid5_check_reshape(struct mddev *mddev)
  {
  	/* For a 2-drive array, the layout and chunk size can be changed
  	 * immediately as not restriping is needed.
  	 * For larger arrays we record the new value - after validation
  	 * to be used by a reshape pass.
  	 */
  	struct r5conf *conf = mddev->private;
  	int new_chunk = mddev->new_chunk_sectors;
  
  	if (mddev->new_layout >= 0 && !algorithm_valid_raid5(mddev->new_layout))
  		return -EINVAL;
  	if (new_chunk > 0) {
  		if (!is_power_of_2(new_chunk))
  			return -EINVAL;
  		if (new_chunk < (PAGE_SIZE>>9))
  			return -EINVAL;
  		if (mddev->array_sectors & (new_chunk-1))
  			/* not factor of array size */
  			return -EINVAL;
  	}
  
  	/* They look valid */
  
  	if (mddev->raid_disks == 2) {
  		/* can make the change immediately */
  		if (mddev->new_layout >= 0) {
  			conf->algorithm = mddev->new_layout;
  			mddev->layout = mddev->new_layout;
  		}
  		if (new_chunk > 0) {
  			conf->chunk_sectors = new_chunk ;
  			mddev->chunk_sectors = new_chunk;
  		}
  		set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
  		md_wakeup_thread(mddev->thread);
  	}
  	return check_reshape(mddev);
  }
  
  static int raid6_check_reshape(struct mddev *mddev)
  {
  	int new_chunk = mddev->new_chunk_sectors;
  
  	if (mddev->new_layout >= 0 && !algorithm_valid_raid6(mddev->new_layout))
  		return -EINVAL;
  	if (new_chunk > 0) {
  		if (!is_power_of_2(new_chunk))
  			return -EINVAL;
  		if (new_chunk < (PAGE_SIZE >> 9))
  			return -EINVAL;
  		if (mddev->array_sectors & (new_chunk-1))
  			/* not factor of array size */
  			return -EINVAL;
  	}
  
  	/* They look valid */
  	return check_reshape(mddev);
  }
  
  static void *raid5_takeover(struct mddev *mddev)
  {
  	/* raid5 can take over:
  	 *  raid0 - if there is only one strip zone - make it a raid4 layout
  	 *  raid1 - if there are two drives.  We need to know the chunk size
  	 *  raid4 - trivial - just use a raid4 layout.
  	 *  raid6 - Providing it is a *_6 layout
  	 */
  	if (mddev->level == 0)
  		return raid45_takeover_raid0(mddev, 5);
  	if (mddev->level == 1)
  		return raid5_takeover_raid1(mddev);
  	if (mddev->level == 4) {
  		mddev->new_layout = ALGORITHM_PARITY_N;
  		mddev->new_level = 5;
  		return setup_conf(mddev);
  	}
  	if (mddev->level == 6)
  		return raid5_takeover_raid6(mddev);
  
  	return ERR_PTR(-EINVAL);
  }
  
  static void *raid4_takeover(struct mddev *mddev)
  {
  	/* raid4 can take over:
  	 *  raid0 - if there is only one strip zone
  	 *  raid5 - if layout is right
  	 */
  	if (mddev->level == 0)
  		return raid45_takeover_raid0(mddev, 4);
  	if (mddev->level == 5 &&
  	    mddev->layout == ALGORITHM_PARITY_N) {
  		mddev->new_layout = 0;
  		mddev->new_level = 4;
  		return setup_conf(mddev);
  	}
  	return ERR_PTR(-EINVAL);
  }
  
  static struct md_personality raid5_personality;
  
  static void *raid6_takeover(struct mddev *mddev)
  {
  	/* Currently can only take over a raid5.  We map the
  	 * personality to an equivalent raid6 personality
  	 * with the Q block at the end.
  	 */
  	int new_layout;
  
  	if (mddev->pers != &raid5_personality)
  		return ERR_PTR(-EINVAL);
  	if (mddev->degraded > 1)
  		return ERR_PTR(-EINVAL);
  	if (mddev->raid_disks > 253)
  		return ERR_PTR(-EINVAL);
  	if (mddev->raid_disks < 3)
  		return ERR_PTR(-EINVAL);
  
  	switch (mddev->layout) {
  	case ALGORITHM_LEFT_ASYMMETRIC:
  		new_layout = ALGORITHM_LEFT_ASYMMETRIC_6;
  		break;
  	case ALGORITHM_RIGHT_ASYMMETRIC:
  		new_layout = ALGORITHM_RIGHT_ASYMMETRIC_6;
  		break;
  	case ALGORITHM_LEFT_SYMMETRIC:
  		new_layout = ALGORITHM_LEFT_SYMMETRIC_6;
  		break;
  	case ALGORITHM_RIGHT_SYMMETRIC:
  		new_layout = ALGORITHM_RIGHT_SYMMETRIC_6;
  		break;
  	case ALGORITHM_PARITY_0:
  		new_layout = ALGORITHM_PARITY_0_6;
  		break;
  	case ALGORITHM_PARITY_N:
  		new_layout = ALGORITHM_PARITY_N;
  		break;
  	default:
  		return ERR_PTR(-EINVAL);
  	}
  	mddev->new_level = 6;
  	mddev->new_layout = new_layout;
  	mddev->delta_disks = 1;
  	mddev->raid_disks += 1;
  	return setup_conf(mddev);
  }
  
  static int raid5_change_consistency_policy(struct mddev *mddev, const char *buf)
  {
  	struct r5conf *conf;
  	int err;
  
  	err = mddev_lock(mddev);
  	if (err)
  		return err;
  	conf = mddev->private;
  	if (!conf) {
  		mddev_unlock(mddev);
  		return -ENODEV;
  	}
  
  	if (strncmp(buf, "ppl", 3) == 0) {
  		/* ppl only works with RAID 5 */
  		if (!raid5_has_ppl(conf) && conf->level == 5) {
  			err = log_init(conf, NULL, true);
  			if (!err) {
  				err = resize_stripes(conf, conf->pool_size);
  				if (err)
  					log_exit(conf);
  			}
  		} else
  			err = -EINVAL;
  	} else if (strncmp(buf, "resync", 6) == 0) {
  		if (raid5_has_ppl(conf)) {
  			mddev_suspend(mddev);
  			log_exit(conf);
  			mddev_resume(mddev);
  			err = resize_stripes(conf, conf->pool_size);
  		} else if (test_bit(MD_HAS_JOURNAL, &conf->mddev->flags) &&
  			   r5l_log_disk_error(conf)) {
  			bool journal_dev_exists = false;
  			struct md_rdev *rdev;
  
  			rdev_for_each(rdev, mddev)
  				if (test_bit(Journal, &rdev->flags)) {
  					journal_dev_exists = true;
  					break;
  				}
  
  			if (!journal_dev_exists) {
  				mddev_suspend(mddev);
  				clear_bit(MD_HAS_JOURNAL, &mddev->flags);
  				mddev_resume(mddev);
  			} else  /* need remove journal device first */
  				err = -EBUSY;
  		} else
  			err = -EINVAL;
  	} else {
  		err = -EINVAL;
  	}
  
  	if (!err)
  		md_update_sb(mddev, 1);
  
  	mddev_unlock(mddev);
  
  	return err;
  }
  
  static int raid5_start(struct mddev *mddev)
  {
  	struct r5conf *conf = mddev->private;
  
  	return r5l_start(conf->log);
  }
  
  static struct md_personality raid6_personality =
  {
  	.name		= "raid6",
  	.level		= 6,
  	.owner		= THIS_MODULE,
  	.make_request	= raid5_make_request,
  	.run		= raid5_run,
  	.start		= raid5_start,
  	.free		= raid5_free,
  	.status		= raid5_status,
  	.error_handler	= raid5_error,
  	.hot_add_disk	= raid5_add_disk,
  	.hot_remove_disk= raid5_remove_disk,
  	.spare_active	= raid5_spare_active,
  	.sync_request	= raid5_sync_request,
  	.resize		= raid5_resize,
  	.size		= raid5_size,
  	.check_reshape	= raid6_check_reshape,
  	.start_reshape  = raid5_start_reshape,
  	.finish_reshape = raid5_finish_reshape,
  	.quiesce	= raid5_quiesce,
  	.takeover	= raid6_takeover,
  	.change_consistency_policy = raid5_change_consistency_policy,
  };
  static struct md_personality raid5_personality =
  {
  	.name		= "raid5",
  	.level		= 5,
  	.owner		= THIS_MODULE,
  	.make_request	= raid5_make_request,
  	.run		= raid5_run,
  	.start		= raid5_start,
  	.free		= raid5_free,
  	.status		= raid5_status,
  	.error_handler	= raid5_error,
  	.hot_add_disk	= raid5_add_disk,
  	.hot_remove_disk= raid5_remove_disk,
  	.spare_active	= raid5_spare_active,
  	.sync_request	= raid5_sync_request,
  	.resize		= raid5_resize,
  	.size		= raid5_size,
  	.check_reshape	= raid5_check_reshape,
  	.start_reshape  = raid5_start_reshape,
  	.finish_reshape = raid5_finish_reshape,
  	.quiesce	= raid5_quiesce,
  	.takeover	= raid5_takeover,
  	.change_consistency_policy = raid5_change_consistency_policy,
  };
  
  static struct md_personality raid4_personality =
  {
  	.name		= "raid4",
  	.level		= 4,
  	.owner		= THIS_MODULE,
  	.make_request	= raid5_make_request,
  	.run		= raid5_run,
  	.start		= raid5_start,
  	.free		= raid5_free,
  	.status		= raid5_status,
  	.error_handler	= raid5_error,
  	.hot_add_disk	= raid5_add_disk,
  	.hot_remove_disk= raid5_remove_disk,
  	.spare_active	= raid5_spare_active,
  	.sync_request	= raid5_sync_request,
  	.resize		= raid5_resize,
  	.size		= raid5_size,
  	.check_reshape	= raid5_check_reshape,
  	.start_reshape  = raid5_start_reshape,
  	.finish_reshape = raid5_finish_reshape,
  	.quiesce	= raid5_quiesce,
  	.takeover	= raid4_takeover,
  	.change_consistency_policy = raid5_change_consistency_policy,
  };
  
  static int __init raid5_init(void)
  {
  	int ret;
  
  	raid5_wq = alloc_workqueue("raid5wq",
  		WQ_UNBOUND|WQ_MEM_RECLAIM|WQ_CPU_INTENSIVE|WQ_SYSFS, 0);
  	if (!raid5_wq)
  		return -ENOMEM;
  
  	ret = cpuhp_setup_state_multi(CPUHP_MD_RAID5_PREPARE,
  				      "md/raid5:prepare",
  				      raid456_cpu_up_prepare,
  				      raid456_cpu_dead);
  	if (ret) {
  		destroy_workqueue(raid5_wq);
  		return ret;
  	}
  	register_md_personality(&raid6_personality);
  	register_md_personality(&raid5_personality);
  	register_md_personality(&raid4_personality);
  	return 0;
  }
  
  static void raid5_exit(void)
  {
  	unregister_md_personality(&raid6_personality);
  	unregister_md_personality(&raid5_personality);
  	unregister_md_personality(&raid4_personality);
  	cpuhp_remove_multi_state(CPUHP_MD_RAID5_PREPARE);
  	destroy_workqueue(raid5_wq);
  }
  
  module_init(raid5_init);
  module_exit(raid5_exit);
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("RAID4/5/6 (striping with parity) personality for MD");
  MODULE_ALIAS("md-personality-4"); /* RAID5 */
  MODULE_ALIAS("md-raid5");
  MODULE_ALIAS("md-raid4");
  MODULE_ALIAS("md-level-5");
  MODULE_ALIAS("md-level-4");
  MODULE_ALIAS("md-personality-8"); /* RAID6 */
  MODULE_ALIAS("md-raid6");
  MODULE_ALIAS("md-level-6");
  
  /* This used to be two separate modules, they were: */
  MODULE_ALIAS("raid5");
  MODULE_ALIAS("raid6");
  