text: /*
   * Copyright (C) 2003 Sistina Software
   * Copyright (C) 2006 Red Hat GmbH
   *
   * This file is released under the GPL.
   */
  
  #include "dm.h"
  
  #include <linux/device-mapper.h>
  
  #include <linux/bio.h>
  #include <linux/completion.h>
  #include <linux/mempool.h>
  #include <linux/module.h>
  #include <linux/sched.h>
  #include <linux/slab.h>
  #include <linux/dm-io.h>
  
  #define DM_MSG_PREFIX "io"
  
  #define DM_IO_MAX_REGIONS	BITS_PER_LONG
  #define MIN_IOS		16
  #define MIN_BIOS	16
  
  struct dm_io_client {
  	mempool_t *pool;
  	struct bio_set *bios;
  };
  
  /*
   * Aligning 'struct io' reduces the number of bits required to store
   * its address.  Refer to store_io_and_region_in_bio() below.
   */
  struct io {
  	unsigned long error_bits;
  	atomic_t count;
  	struct completion *wait;
  	struct dm_io_client *client;
  	io_notify_fn callback;
  	void *context;
  	void *vma_invalidate_address;
  	unsigned long vma_invalidate_size;
  } __attribute__((aligned(DM_IO_MAX_REGIONS)));
  
  static struct kmem_cache *_dm_io_cache;
  
  /*
   * Create a client with mempool and bioset.
   */
  struct dm_io_client *dm_io_client_create(void)
  {
  	struct dm_io_client *client;
  
  	client = kmalloc(sizeof(*client), GFP_KERNEL);
  	if (!client)
  		return ERR_PTR(-ENOMEM);
  
  	client->pool = mempool_create_slab_pool(MIN_IOS, _dm_io_cache);
  	if (!client->pool)
  		goto bad;
  
  	client->bios = bioset_create(MIN_BIOS, 0);
  	if (!client->bios)
  		goto bad;
  
  	return client;
  
     bad:
  	if (client->pool)
  		mempool_destroy(client->pool);
  	kfree(client);
  	return ERR_PTR(-ENOMEM);
  }
  EXPORT_SYMBOL(dm_io_client_create);
  
  void dm_io_client_destroy(struct dm_io_client *client)
  {
  	mempool_destroy(client->pool);
  	bioset_free(client->bios);
  	kfree(client);
  }
  EXPORT_SYMBOL(dm_io_client_destroy);
  
  /*-----------------------------------------------------------------
   * We need to keep track of which region a bio is doing io for.
   * To avoid a memory allocation to store just 5 or 6 bits, we
   * ensure the 'struct io' pointer is aligned so enough low bits are
   * always zero and then combine it with the region number directly in
   * bi_private.
   *---------------------------------------------------------------*/
  static void store_io_and_region_in_bio(struct bio *bio, struct io *io,
  				       unsigned region)
  {
  	if (unlikely(!IS_ALIGNED((unsigned long)io, DM_IO_MAX_REGIONS))) {
  		DMCRIT("Unaligned struct io pointer %p", io);
  		BUG();
  	}
  
  	bio->bi_private = (void *)((unsigned long)io | region);
  }
  
  static void retrieve_io_and_region_from_bio(struct bio *bio, struct io **io,
  				       unsigned *region)
  {
  	unsigned long val = (unsigned long)bio->bi_private;
  
  	*io = (void *)(val & -(unsigned long)DM_IO_MAX_REGIONS);
  	*region = val & (DM_IO_MAX_REGIONS - 1);
  }
  
  /*-----------------------------------------------------------------
   * We need an io object to keep track of the number of bios that
   * have been dispatched for a particular io.
   *---------------------------------------------------------------*/
  static void dec_count(struct io *io, unsigned int region, int error)
  {
  	if (error)
  		set_bit(region, &io->error_bits);
  
  	if (atomic_dec_and_test(&io->count)) {
  		if (io->vma_invalidate_size)
  			invalidate_kernel_vmap_range(io->vma_invalidate_address,
  						     io->vma_invalidate_size);
  
  		if (io->wait)
  			complete(io->wait);
  
  		else {
  			unsigned long r = io->error_bits;
  			io_notify_fn fn = io->callback;
  			void *context = io->context;
  
  			mempool_free(io, io->client->pool);
  			fn(r, context);
  		}
  	}
  }
  
  static void endio(struct bio *bio, int error)
  {
  	struct io *io;
  	unsigned region;
  
  	if (error && bio_data_dir(bio) == READ)
  		zero_fill_bio(bio);
  
  	/*
  	 * The bio destructor in bio_put() may use the io object.
  	 */
  	retrieve_io_and_region_from_bio(bio, &io, &region);
  
  	bio_put(bio);
  
  	dec_count(io, region, error);
  }
  
  /*-----------------------------------------------------------------
   * These little objects provide an abstraction for getting a new
   * destination page for io.
   *---------------------------------------------------------------*/
  struct dpages {
  	void (*get_page)(struct dpages *dp,
  			 struct page **p, unsigned long *len, unsigned *offset);
  	void (*next_page)(struct dpages *dp);
  
  	unsigned context_u;
  	void *context_ptr;
  
  	void *vma_invalidate_address;
  	unsigned long vma_invalidate_size;
  };
  
  /*
   * Functions for getting the pages from a list.
   */
  static void list_get_page(struct dpages *dp,
  		  struct page **p, unsigned long *len, unsigned *offset)
  {
  	unsigned o = dp->context_u;
  	struct page_list *pl = (struct page_list *) dp->context_ptr;
  
  	*p = pl->page;
  	*len = PAGE_SIZE - o;
  	*offset = o;
  }
  
  static void list_next_page(struct dpages *dp)
  {
  	struct page_list *pl = (struct page_list *) dp->context_ptr;
  	dp->context_ptr = pl->next;
  	dp->context_u = 0;
  }
  
  static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offset)
  {
  	dp->get_page = list_get_page;
  	dp->next_page = list_next_page;
  	dp->context_u = offset;
  	dp->context_ptr = pl;
  }
  
  /*
   * Functions for getting the pages from a bvec.
   */
  static void bvec_get_page(struct dpages *dp,
  		  struct page **p, unsigned long *len, unsigned *offset)
  {
  	struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
  	*p = bvec->bv_page;
  	*len = bvec->bv_len;
  	*offset = bvec->bv_offset;
  }
  
  static void bvec_next_page(struct dpages *dp)
  {
  	struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
  	dp->context_ptr = bvec + 1;
  }
  
  static void bvec_dp_init(struct dpages *dp, struct bio_vec *bvec)
  {
  	dp->get_page = bvec_get_page;
  	dp->next_page = bvec_next_page;
  	dp->context_ptr = bvec;
  }
  
  /*
   * Functions for getting the pages from a VMA.
   */
  static void vm_get_page(struct dpages *dp,
  		 struct page **p, unsigned long *len, unsigned *offset)
  {
  	*p = vmalloc_to_page(dp->context_ptr);
  	*offset = dp->context_u;
  	*len = PAGE_SIZE - dp->context_u;
  }
  
  static void vm_next_page(struct dpages *dp)
  {
  	dp->context_ptr += PAGE_SIZE - dp->context_u;
  	dp->context_u = 0;
  }
  
  static void vm_dp_init(struct dpages *dp, void *data)
  {
  	dp->get_page = vm_get_page;
  	dp->next_page = vm_next_page;
  	dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
  	dp->context_ptr = data;
  }
  
  /*
   * Functions for getting the pages from kernel memory.
   */
  static void km_get_page(struct dpages *dp, struct page **p, unsigned long *len,
  			unsigned *offset)
  {
  	*p = virt_to_page(dp->context_ptr);
  	*offset = dp->context_u;
  	*len = PAGE_SIZE - dp->context_u;
  }
  
  static void km_next_page(struct dpages *dp)
  {
  	dp->context_ptr += PAGE_SIZE - dp->context_u;
  	dp->context_u = 0;
  }
  
  static void km_dp_init(struct dpages *dp, void *data)
  {
  	dp->get_page = km_get_page;
  	dp->next_page = km_next_page;
  	dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
  	dp->context_ptr = data;
  }
  
  /*-----------------------------------------------------------------
   * IO routines that accept a list of pages.
   *---------------------------------------------------------------*/
  static void do_region(int rw, unsigned region, struct dm_io_region *where,
  		      struct dpages *dp, struct io *io)
  {
  	struct bio *bio;
  	struct page *page;
  	unsigned long len;
  	unsigned offset;
  	unsigned num_bvecs;
  	sector_t remaining = where->count;
  	struct request_queue *q = bdev_get_queue(where->bdev);
  	unsigned short logical_block_size = queue_logical_block_size(q);
  	sector_t num_sectors;
  
  	/*
  	 * where->count may be zero if rw holds a flush and we need to
  	 * send a zero-sized flush.
  	 */
  	do {
  		/*
  		 * Allocate a suitably sized-bio.
  		 */
  		if ((rw & REQ_DISCARD) || (rw & REQ_WRITE_SAME))
  			num_bvecs = 1;
  		else
  			num_bvecs = min_t(int, bio_get_nr_vecs(where->bdev),
  					  dm_sector_div_up(remaining, (PAGE_SIZE >> SECTOR_SHIFT)));
  
  		bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
  		bio->bi_sector = where->sector + (where->count - remaining);
  		bio->bi_bdev = where->bdev;
  		bio->bi_end_io = endio;
  		store_io_and_region_in_bio(bio, io, region);
  
  		if (rw & REQ_DISCARD) {
  			num_sectors = min_t(sector_t, q->limits.max_discard_sectors, remaining);
  			bio->bi_size = num_sectors << SECTOR_SHIFT;
  			remaining -= num_sectors;
  		} else if (rw & REQ_WRITE_SAME) {
  			/*
  			 * WRITE SAME only uses a single page.
  			 */
  			dp->get_page(dp, &page, &len, &offset);
  			bio_add_page(bio, page, logical_block_size, offset);
  			num_sectors = min_t(sector_t, q->limits.max_write_same_sectors, remaining);
  			bio->bi_size = num_sectors << SECTOR_SHIFT;
  
  			offset = 0;
  			remaining -= num_sectors;
  			dp->next_page(dp);
  		} else while (remaining) {
  			/*
  			 * Try and add as many pages as possible.
  			 */
  			dp->get_page(dp, &page, &len, &offset);
  			len = min(len, to_bytes(remaining));
  			if (!bio_add_page(bio, page, len, offset))
  				break;
  
  			offset = 0;
  			remaining -= to_sector(len);
  			dp->next_page(dp);
  		}
  
  		atomic_inc(&io->count);
  		submit_bio(rw, bio);
  	} while (remaining);
  }
  
  static void dispatch_io(int rw, unsigned int num_regions,
  			struct dm_io_region *where, struct dpages *dp,
  			struct io *io, int sync)
  {
  	int i;
  	struct dpages old_pages = *dp;
  
  	BUG_ON(num_regions > DM_IO_MAX_REGIONS);
  
  	if (sync)
  		rw |= REQ_SYNC;
  
  	/*
  	 * For multiple regions we need to be careful to rewind
  	 * the dp object for each call to do_region.
  	 */
  	for (i = 0; i < num_regions; i++) {
  		*dp = old_pages;
  		if (where[i].count || (rw & REQ_FLUSH))
  			do_region(rw, i, where + i, dp, io);
  	}
  
  	/*
  	 * Drop the extra reference that we were holding to avoid
  	 * the io being completed too early.
  	 */
  	dec_count(io, 0, 0);
  }
  
  static int sync_io(struct dm_io_client *client, unsigned int num_regions,
  		   struct dm_io_region *where, int rw, struct dpages *dp,
  		   unsigned long *error_bits)
  {
  	/*
  	 * gcc <= 4.3 can't do the alignment for stack variables, so we must
  	 * align it on our own.
  	 * volatile prevents the optimizer from removing or reusing
  	 * "io_" field from the stack frame (allowed in ANSI C).
  	 */
  	volatile char io_[sizeof(struct io) + __alignof__(struct io) - 1];
  	struct io *io = (struct io *)PTR_ALIGN(&io_, __alignof__(struct io));
  	DECLARE_COMPLETION_ONSTACK(wait);
  
  	if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
  		WARN_ON(1);
  		return -EIO;
  	}
  
  	io->error_bits = 0;
  	atomic_set(&io->count, 1); /* see dispatch_io() */
  	io->wait = &wait;
  	io->client = client;
  
  	io->vma_invalidate_address = dp->vma_invalidate_address;
  	io->vma_invalidate_size = dp->vma_invalidate_size;
  
  	dispatch_io(rw, num_regions, where, dp, io, 1);
  
  	wait_for_completion_io(&wait);
  
  	if (error_bits)
  		*error_bits = io->error_bits;
  
  	return io->error_bits ? -EIO : 0;
  }
  
  static int async_io(struct dm_io_client *client, unsigned int num_regions,
  		    struct dm_io_region *where, int rw, struct dpages *dp,
  		    io_notify_fn fn, void *context)
  {
  	struct io *io;
  
  	if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
  		WARN_ON(1);
  		fn(1, context);
  		return -EIO;
  	}
  
  	io = mempool_alloc(client->pool, GFP_NOIO);
  	io->error_bits = 0;
  	atomic_set(&io->count, 1); /* see dispatch_io() */
  	io->wait = NULL;
  	io->client = client;
  	io->callback = fn;
  	io->context = context;
  
  	io->vma_invalidate_address = dp->vma_invalidate_address;
  	io->vma_invalidate_size = dp->vma_invalidate_size;
  
  	dispatch_io(rw, num_regions, where, dp, io, 0);
  	return 0;
  }
  
  static int dp_init(struct dm_io_request *io_req, struct dpages *dp,
  		   unsigned long size)
  {
  	/* Set up dpages based on memory type */
  
  	dp->vma_invalidate_address = NULL;
  	dp->vma_invalidate_size = 0;
  
  	switch (io_req->mem.type) {
  	case DM_IO_PAGE_LIST:
  		list_dp_init(dp, io_req->mem.ptr.pl, io_req->mem.offset);
  		break;
  
  	case DM_IO_BVEC:
  		bvec_dp_init(dp, io_req->mem.ptr.bvec);
  		break;
  
  	case DM_IO_VMA:
  		flush_kernel_vmap_range(io_req->mem.ptr.vma, size);
  		if ((io_req->bi_rw & RW_MASK) == READ) {
  			dp->vma_invalidate_address = io_req->mem.ptr.vma;
  			dp->vma_invalidate_size = size;
  		}
  		vm_dp_init(dp, io_req->mem.ptr.vma);
  		break;
  
  	case DM_IO_KMEM:
  		km_dp_init(dp, io_req->mem.ptr.addr);
  		break;
  
  	default:
  		return -EINVAL;
  	}
  
  	return 0;
  }
  
  /*
   * New collapsed (a)synchronous interface.
   *
   * If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
   * the queue with blk_unplug() some time later or set REQ_SYNC in
  io_req->bi_rw. If you fail to do one of these, the IO will be submitted to
   * the disk after q->unplug_delay, which defaults to 3ms in blk-settings.c.
   */
  int dm_io(struct dm_io_request *io_req, unsigned num_regions,
  	  struct dm_io_region *where, unsigned long *sync_error_bits)
  {
  	int r;
  	struct dpages dp;
  
  	r = dp_init(io_req, &dp, (unsigned long)where->count << SECTOR_SHIFT);
  	if (r)
  		return r;
  
  	if (!io_req->notify.fn)
  		return sync_io(io_req->client, num_regions, where,
  			       io_req->bi_rw, &dp, sync_error_bits);
  
  	return async_io(io_req->client, num_regions, where, io_req->bi_rw,
  			&dp, io_req->notify.fn, io_req->notify.context);
  }
  EXPORT_SYMBOL(dm_io);
  
  int __init dm_io_init(void)
  {
  	_dm_io_cache = KMEM_CACHE(io, 0);
  	if (!_dm_io_cache)
  		return -ENOMEM;
  
  	return 0;
  }
  
  void dm_io_exit(void)
  {
  	kmem_cache_destroy(_dm_io_cache);
  	_dm_io_cache = NULL;
  }
  