text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * Add configfs and memory store: Kyungchan Koh <kkc6196@fb.com> and
   * Shaohua Li <shli@fb.com>
   */
  #include <linux/module.h>
  
  #include <linux/moduleparam.h>
  #include <linux/sched.h>
  #include <linux/fs.h>
  #include <linux/init.h>
  #include "null_blk.h"
  
  #define PAGE_SECTORS_SHIFT	(PAGE_SHIFT - SECTOR_SHIFT)
  #define PAGE_SECTORS		(1 << PAGE_SECTORS_SHIFT)
  #define SECTOR_MASK		(PAGE_SECTORS - 1)
  
  #define FREE_BATCH		16
  
  #define TICKS_PER_SEC		50ULL
  #define TIMER_INTERVAL		(NSEC_PER_SEC / TICKS_PER_SEC)
  
  #ifdef CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION
  static DECLARE_FAULT_ATTR(null_timeout_attr);
  static DECLARE_FAULT_ATTR(null_requeue_attr);
  #endif
  
  static inline u64 mb_per_tick(int mbps)
  {
  	return (1 << 20) / TICKS_PER_SEC * ((u64) mbps);
  }
  
  /*
   * Status flags for nullb_device.
   *
   * CONFIGURED:	Device has been configured and turned on. Cannot reconfigure.
   * UP:		Device is currently on and visible in userspace.
   * THROTTLED:	Device is being throttled.
   * CACHE:	Device is using a write-back cache.
   */
  enum nullb_device_flags {
  	NULLB_DEV_FL_CONFIGURED	= 0,
  	NULLB_DEV_FL_UP		= 1,
  	NULLB_DEV_FL_THROTTLED	= 2,
  	NULLB_DEV_FL_CACHE	= 3,
  };
  
  #define MAP_SZ		((PAGE_SIZE >> SECTOR_SHIFT) + 2)
  /*
   * nullb_page is a page in memory for nullb devices.
   *
   * @page:	The page holding the data.
   * @bitmap:	The bitmap represents which sector in the page has data.
   *		Each bit represents one block size. For example, sector 8
   *		will use the 7th bit
   * The highest 2 bits of bitmap are for special purpose. LOCK means the cache
   * page is being flushing to storage. FREE means the cache page is freed and
   * should be skipped from flushing to storage. Please see
   * null_make_cache_space
   */
  struct nullb_page {
  	struct page *page;
  	DECLARE_BITMAP(bitmap, MAP_SZ);
  };
  #define NULLB_PAGE_LOCK (MAP_SZ - 1)
  #define NULLB_PAGE_FREE (MAP_SZ - 2)
  
  static LIST_HEAD(nullb_list);
  static struct mutex lock;
  static int null_major;
  static DEFINE_IDA(nullb_indexes);
  static struct blk_mq_tag_set tag_set;
  
  enum {
  	NULL_IRQ_NONE		= 0,
  	NULL_IRQ_SOFTIRQ	= 1,
  	NULL_IRQ_TIMER		= 2,
  };
  
  enum {
  	NULL_Q_BIO		= 0,
  	NULL_Q_RQ		= 1,
  	NULL_Q_MQ		= 2,
  };
  
  static int g_no_sched;
  module_param_named(no_sched, g_no_sched, int, 0444);
  MODULE_PARM_DESC(no_sched, "No io scheduler");
  
  static int g_submit_queues = 1;
  module_param_named(submit_queues, g_submit_queues, int, 0444);
  MODULE_PARM_DESC(submit_queues, "Number of submission queues");
  
  static int g_home_node = NUMA_NO_NODE;
  module_param_named(home_node, g_home_node, int, 0444);
  MODULE_PARM_DESC(home_node, "Home node for the device");
  
  #ifdef CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION
  static char g_timeout_str[80];
  module_param_string(timeout, g_timeout_str, sizeof(g_timeout_str), 0444);
  
  static char g_requeue_str[80];
  module_param_string(requeue, g_requeue_str, sizeof(g_requeue_str), 0444);
  #endif
  
  static int g_queue_mode = NULL_Q_MQ;
  
  static int null_param_store_val(const char *str, int *val, int min, int max)
  {
  	int ret, new_val;
  
  	ret = kstrtoint(str, 10, &new_val);
  	if (ret)
  		return -EINVAL;
  
  	if (new_val < min || new_val > max)
  		return -EINVAL;
  
  	*val = new_val;
  	return 0;
  }
  
  static int null_set_queue_mode(const char *str, const struct kernel_param *kp)
  {
  	return null_param_store_val(str, &g_queue_mode, NULL_Q_BIO, NULL_Q_MQ);
  }
  
  static const struct kernel_param_ops null_queue_mode_param_ops = {
  	.set	= null_set_queue_mode,
  	.get	= param_get_int,
  };
  
  device_param_cb(queue_mode, &null_queue_mode_param_ops, &g_queue_mode, 0444);
  MODULE_PARM_DESC(queue_mode, "Block interface to use (0=bio,1=rq,2=multiqueue)");
  
  static int g_gb = 250;
  module_param_named(gb, g_gb, int, 0444);
  MODULE_PARM_DESC(gb, "Size in GB");
  
  static int g_bs = 512;
  module_param_named(bs, g_bs, int, 0444);
  MODULE_PARM_DESC(bs, "Block size (in bytes)");
  
  static int nr_devices = 1;
  module_param(nr_devices, int, 0444);
  MODULE_PARM_DESC(nr_devices, "Number of devices to register");
  
  static bool g_blocking;
  module_param_named(blocking, g_blocking, bool, 0444);
  MODULE_PARM_DESC(blocking, "Register as a blocking blk-mq driver device");
  
  static bool shared_tags;
  module_param(shared_tags, bool, 0444);
  MODULE_PARM_DESC(shared_tags, "Share tag set between devices for blk-mq");
  
  static int g_irqmode = NULL_IRQ_SOFTIRQ;
  
  static int null_set_irqmode(const char *str, const struct kernel_param *kp)
  {
  	return null_param_store_val(str, &g_irqmode, NULL_IRQ_NONE,
  					NULL_IRQ_TIMER);
  }
  
  static const struct kernel_param_ops null_irqmode_param_ops = {
  	.set	= null_set_irqmode,
  	.get	= param_get_int,
  };
  
  device_param_cb(irqmode, &null_irqmode_param_ops, &g_irqmode, 0444);
  MODULE_PARM_DESC(irqmode, "IRQ completion handler. 0-none, 1-softirq, 2-timer");
  
  static unsigned long g_completion_nsec = 10000;
  module_param_named(completion_nsec, g_completion_nsec, ulong, 0444);
  MODULE_PARM_DESC(completion_nsec, "Time in ns to complete a request in hardware. Default: 10,000ns");
  
  static int g_hw_queue_depth = 64;
  module_param_named(hw_queue_depth, g_hw_queue_depth, int, 0444);
  MODULE_PARM_DESC(hw_queue_depth, "Queue depth for each hardware queue. Default: 64");
  
  static bool g_use_per_node_hctx;
  module_param_named(use_per_node_hctx, g_use_per_node_hctx, bool, 0444);
  MODULE_PARM_DESC(use_per_node_hctx, "Use per-node allocation for hardware context queues. Default: false");
  
  static bool g_zoned;
  module_param_named(zoned, g_zoned, bool, S_IRUGO);
  MODULE_PARM_DESC(zoned, "Make device as a host-managed zoned block device. Default: false");
  
  static unsigned long g_zone_size = 256;
  module_param_named(zone_size, g_zone_size, ulong, S_IRUGO);
  MODULE_PARM_DESC(zone_size, "Zone size in MB when block device is zoned. Must be power-of-two: Default: 256");
  
  static unsigned int g_zone_nr_conv;
  module_param_named(zone_nr_conv, g_zone_nr_conv, uint, 0444);
  MODULE_PARM_DESC(zone_nr_conv, "Number of conventional zones when block device is zoned. Default: 0");
  
  static struct nullb_device *null_alloc_dev(void);
  static void null_free_dev(struct nullb_device *dev);
  static void null_del_dev(struct nullb *nullb);
  static int null_add_dev(struct nullb_device *dev);
  static void null_free_device_storage(struct nullb_device *dev, bool is_cache);
  
  static inline struct nullb_device *to_nullb_device(struct config_item *item)
  {
  	return item ? container_of(item, struct nullb_device, item) : NULL;
  }
  
  static inline ssize_t nullb_device_uint_attr_show(unsigned int val, char *page)
  {
  	return snprintf(page, PAGE_SIZE, "%u\n", val);
  }
  
  static inline ssize_t nullb_device_ulong_attr_show(unsigned long val,
  	char *page)
  {
  	return snprintf(page, PAGE_SIZE, "%lu\n", val);
  }
  
  static inline ssize_t nullb_device_bool_attr_show(bool val, char *page)
  {
  	return snprintf(page, PAGE_SIZE, "%u\n", val);
  }
  
  static ssize_t nullb_device_uint_attr_store(unsigned int *val,
  	const char *page, size_t count)
  {
  	unsigned int tmp;
  	int result;
  
  	result = kstrtouint(page, 0, &tmp);
  	if (result)
  		return result;
  
  	*val = tmp;
  	return count;
  }
  
  static ssize_t nullb_device_ulong_attr_store(unsigned long *val,
  	const char *page, size_t count)
  {
  	int result;
  	unsigned long tmp;
  
  	result = kstrtoul(page, 0, &tmp);
  	if (result)
  		return result;
  
  	*val = tmp;
  	return count;
  }
  
  static ssize_t nullb_device_bool_attr_store(bool *val, const char *page,
  	size_t count)
  {
  	bool tmp;
  	int result;
  
  	result = kstrtobool(page,  &tmp);
  	if (result)
  		return result;
  
  	*val = tmp;
  	return count;
  }
  
  /* The following macro should only be used with TYPE = {uint, ulong, bool}. */
  #define NULLB_DEVICE_ATTR(NAME, TYPE)						\
  static ssize_t									\
  nullb_device_##NAME##_show(struct config_item *item, char *page)		\
  {										\
  	return nullb_device_##TYPE##_attr_show(					\
  				to_nullb_device(item)->NAME, page);		\
  }										\
  static ssize_t									\
  nullb_device_##NAME##_store(struct config_item *item, const char *page,		\
  			    size_t count)					\
  {										\
  	if (test_bit(NULLB_DEV_FL_CONFIGURED, &to_nullb_device(item)->flags))	\
  		return -EBUSY;							\
  	return nullb_device_##TYPE##_attr_store(				\
  			&to_nullb_device(item)->NAME, page, count);		\
  }										\
  CONFIGFS_ATTR(nullb_device_, NAME);
  
  NULLB_DEVICE_ATTR(size, ulong);
  NULLB_DEVICE_ATTR(completion_nsec, ulong);
  NULLB_DEVICE_ATTR(submit_queues, uint);
  NULLB_DEVICE_ATTR(home_node, uint);
  NULLB_DEVICE_ATTR(queue_mode, uint);
  NULLB_DEVICE_ATTR(blocksize, uint);
  NULLB_DEVICE_ATTR(irqmode, uint);
  NULLB_DEVICE_ATTR(hw_queue_depth, uint);
  NULLB_DEVICE_ATTR(index, uint);
  NULLB_DEVICE_ATTR(blocking, bool);
  NULLB_DEVICE_ATTR(use_per_node_hctx, bool);
  NULLB_DEVICE_ATTR(memory_backed, bool);
  NULLB_DEVICE_ATTR(discard, bool);
  NULLB_DEVICE_ATTR(mbps, uint);
  NULLB_DEVICE_ATTR(cache_size, ulong);
  NULLB_DEVICE_ATTR(zoned, bool);
  NULLB_DEVICE_ATTR(zone_size, ulong);
  NULLB_DEVICE_ATTR(zone_nr_conv, uint);
  
  static ssize_t nullb_device_power_show(struct config_item *item, char *page)
  {
  	return nullb_device_bool_attr_show(to_nullb_device(item)->power, page);
  }
  
  static ssize_t nullb_device_power_store(struct config_item *item,
  				     const char *page, size_t count)
  {
  	struct nullb_device *dev = to_nullb_device(item);
  	bool newp = false;
  	ssize_t ret;
  
  	ret = nullb_device_bool_attr_store(&newp, page, count);
  	if (ret < 0)
  		return ret;
  
  	if (!dev->power && newp) {
  		if (test_and_set_bit(NULLB_DEV_FL_UP, &dev->flags))
  			return count;
  		if (null_add_dev(dev)) {
  			clear_bit(NULLB_DEV_FL_UP, &dev->flags);
  			return -ENOMEM;
  		}
  
  		set_bit(NULLB_DEV_FL_CONFIGURED, &dev->flags);
  		dev->power = newp;
  	} else if (dev->power && !newp) {
  		mutex_lock(&lock);
  		dev->power = newp;
  		null_del_dev(dev->nullb);
  		mutex_unlock(&lock);
  		clear_bit(NULLB_DEV_FL_UP, &dev->flags);
  		clear_bit(NULLB_DEV_FL_CONFIGURED, &dev->flags);
  	}
  
  	return count;
  }
  
  CONFIGFS_ATTR(nullb_device_, power);
  
  static ssize_t nullb_device_badblocks_show(struct config_item *item, char *page)
  {
  	struct nullb_device *t_dev = to_nullb_device(item);
  
  	return badblocks_show(&t_dev->badblocks, page, 0);
  }
  
  static ssize_t nullb_device_badblocks_store(struct config_item *item,
  				     const char *page, size_t count)
  {
  	struct nullb_device *t_dev = to_nullb_device(item);
  	char *orig, *buf, *tmp;
  	u64 start, end;
  	int ret;
  
  	orig = kstrndup(page, count, GFP_KERNEL);
  	if (!orig)
  		return -ENOMEM;
  
  	buf = strstrip(orig);
  
  	ret = -EINVAL;
  	if (buf[0] != '+' && buf[0] != '-')
  		goto out;
  	tmp = strchr(&buf[1], '-');
  	if (!tmp)
  		goto out;
  	*tmp = '\0';
  	ret = kstrtoull(buf + 1, 0, &start);
  	if (ret)
  		goto out;
  	ret = kstrtoull(tmp + 1, 0, &end);
  	if (ret)
  		goto out;
  	ret = -EINVAL;
  	if (start > end)
  		goto out;
  	/* enable badblocks */
  	cmpxchg(&t_dev->badblocks.shift, -1, 0);
  	if (buf[0] == '+')
  		ret = badblocks_set(&t_dev->badblocks, start,
  			end - start + 1, 1);
  	else
  		ret = badblocks_clear(&t_dev->badblocks, start,
  			end - start + 1);
  	if (ret == 0)
  		ret = count;
  out:
  	kfree(orig);
  	return ret;
  }
  CONFIGFS_ATTR(nullb_device_, badblocks);
  
  static struct configfs_attribute *nullb_device_attrs[] = {
  	&nullb_device_attr_size,
  	&nullb_device_attr_completion_nsec,
  	&nullb_device_attr_submit_queues,
  	&nullb_device_attr_home_node,
  	&nullb_device_attr_queue_mode,
  	&nullb_device_attr_blocksize,
  	&nullb_device_attr_irqmode,
  	&nullb_device_attr_hw_queue_depth,
  	&nullb_device_attr_index,
  	&nullb_device_attr_blocking,
  	&nullb_device_attr_use_per_node_hctx,
  	&nullb_device_attr_power,
  	&nullb_device_attr_memory_backed,
  	&nullb_device_attr_discard,
  	&nullb_device_attr_mbps,
  	&nullb_device_attr_cache_size,
  	&nullb_device_attr_badblocks,
  	&nullb_device_attr_zoned,
  	&nullb_device_attr_zone_size,
  	&nullb_device_attr_zone_nr_conv,
  	NULL,
  };
  
  static void nullb_device_release(struct config_item *item)
  {
  	struct nullb_device *dev = to_nullb_device(item);
  
  	null_free_device_storage(dev, false);
  	null_free_dev(dev);
  }
  
  static struct configfs_item_operations nullb_device_ops = {
  	.release	= nullb_device_release,
  };
  
  static const struct config_item_type nullb_device_type = {
  	.ct_item_ops	= &nullb_device_ops,
  	.ct_attrs	= nullb_device_attrs,
  	.ct_owner	= THIS_MODULE,
  };
  
  static struct
  config_item *nullb_group_make_item(struct config_group *group, const char *name)
  {
  	struct nullb_device *dev;
  
  	dev = null_alloc_dev();
  	if (!dev)
  		return ERR_PTR(-ENOMEM);
  
  	config_item_init_type_name(&dev->item, name, &nullb_device_type);
  
  	return &dev->item;
  }
  
  static void
  nullb_group_drop_item(struct config_group *group, struct config_item *item)
  {
  	struct nullb_device *dev = to_nullb_device(item);
  
  	if (test_and_clear_bit(NULLB_DEV_FL_UP, &dev->flags)) {
  		mutex_lock(&lock);
  		dev->power = false;
  		null_del_dev(dev->nullb);
  		mutex_unlock(&lock);
  	}
  
  	config_item_put(item);
  }
  
  static ssize_t memb_group_features_show(struct config_item *item, char *page)
  {
  	return snprintf(page, PAGE_SIZE, "memory_backed,discard,bandwidth,cache,badblocks,zoned,zone_size\n");
  }
  
  CONFIGFS_ATTR_RO(memb_group_, features);
  
  static struct configfs_attribute *nullb_group_attrs[] = {
  	&memb_group_attr_features,
  	NULL,
  };
  
  static struct configfs_group_operations nullb_group_ops = {
  	.make_item	= nullb_group_make_item,
  	.drop_item	= nullb_group_drop_item,
  };
  
  static const struct config_item_type nullb_group_type = {
  	.ct_group_ops	= &nullb_group_ops,
  	.ct_attrs	= nullb_group_attrs,
  	.ct_owner	= THIS_MODULE,
  };
  
  static struct configfs_subsystem nullb_subsys = {
  	.su_group = {
  		.cg_item = {
  			.ci_namebuf = "nullb",
  			.ci_type = &nullb_group_type,
  		},
  	},
  };
  
  static inline int null_cache_active(struct nullb *nullb)
  {
  	return test_bit(NULLB_DEV_FL_CACHE, &nullb->dev->flags);
  }
  
  static struct nullb_device *null_alloc_dev(void)
  {
  	struct nullb_device *dev;
  
  	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
  	if (!dev)
  		return NULL;
  	INIT_RADIX_TREE(&dev->data, GFP_ATOMIC);
  	INIT_RADIX_TREE(&dev->cache, GFP_ATOMIC);
  	if (badblocks_init(&dev->badblocks, 0)) {
  		kfree(dev);
  		return NULL;
  	}
  
  	dev->size = g_gb * 1024;
  	dev->completion_nsec = g_completion_nsec;
  	dev->submit_queues = g_submit_queues;
  	dev->home_node = g_home_node;
  	dev->queue_mode = g_queue_mode;
  	dev->blocksize = g_bs;
  	dev->irqmode = g_irqmode;
  	dev->hw_queue_depth = g_hw_queue_depth;
  	dev->blocking = g_blocking;
  	dev->use_per_node_hctx = g_use_per_node_hctx;
  	dev->zoned = g_zoned;
  	dev->zone_size = g_zone_size;
  	dev->zone_nr_conv = g_zone_nr_conv;
  	return dev;
  }
  
  static void null_free_dev(struct nullb_device *dev)
  {
  	if (!dev)
  		return;
  
  	null_zone_exit(dev);
  	badblocks_exit(&dev->badblocks);
  	kfree(dev);
  }
  
  static void put_tag(struct nullb_queue *nq, unsigned int tag)
  {
  	clear_bit_unlock(tag, nq->tag_map);
  
  	if (waitqueue_active(&nq->wait))
  		wake_up(&nq->wait);
  }
  
  static unsigned int get_tag(struct nullb_queue *nq)
  {
  	unsigned int tag;
  
  	do {
  		tag = find_first_zero_bit(nq->tag_map, nq->queue_depth);
  		if (tag >= nq->queue_depth)
  			return -1U;
  	} while (test_and_set_bit_lock(tag, nq->tag_map));
  
  	return tag;
  }
  
  static void free_cmd(struct nullb_cmd *cmd)
  {
  	put_tag(cmd->nq, cmd->tag);
  }
  
  static enum hrtimer_restart null_cmd_timer_expired(struct hrtimer *timer);
  
  static struct nullb_cmd *__alloc_cmd(struct nullb_queue *nq)
  {
  	struct nullb_cmd *cmd;
  	unsigned int tag;
  
  	tag = get_tag(nq);
  	if (tag != -1U) {
  		cmd = &nq->cmds[tag];
  		cmd->tag = tag;
  		cmd->nq = nq;
  		if (nq->dev->irqmode == NULL_IRQ_TIMER) {
  			hrtimer_init(&cmd->timer, CLOCK_MONOTONIC,
  				     HRTIMER_MODE_REL);
  			cmd->timer.function = null_cmd_timer_expired;
  		}
  		return cmd;
  	}
  
  	return NULL;
  }
  
  static struct nullb_cmd *alloc_cmd(struct nullb_queue *nq, int can_wait)
  {
  	struct nullb_cmd *cmd;
  	DEFINE_WAIT(wait);
  
  	cmd = __alloc_cmd(nq);
  	if (cmd || !can_wait)
  		return cmd;
  
  	do {
  		prepare_to_wait(&nq->wait, &wait, TASK_UNINTERRUPTIBLE);
  		cmd = __alloc_cmd(nq);
  		if (cmd)
  			break;
  
  		io_schedule();
  	} while (1);
  
  	finish_wait(&nq->wait, &wait);
  	return cmd;
  }
  
  static void end_cmd(struct nullb_cmd *cmd)
  {
  	int queue_mode = cmd->nq->dev->queue_mode;
  
  	switch (queue_mode)  {
  	case NULL_Q_MQ:
  		blk_mq_end_request(cmd->rq, cmd->error);
  		return;
  	case NULL_Q_BIO:
  		cmd->bio->bi_status = cmd->error;
  		bio_endio(cmd->bio);
  		break;
  	}
  
  	free_cmd(cmd);
  }
  
  static enum hrtimer_restart null_cmd_timer_expired(struct hrtimer *timer)
  {
  	end_cmd(container_of(timer, struct nullb_cmd, timer));
  
  	return HRTIMER_NORESTART;
  }
  
  static void null_cmd_end_timer(struct nullb_cmd *cmd)
  {
  	ktime_t kt = cmd->nq->dev->completion_nsec;
  
  	hrtimer_start(&cmd->timer, kt, HRTIMER_MODE_REL);
  }
  
  static void null_complete_rq(struct request *rq)
  {
  	end_cmd(blk_mq_rq_to_pdu(rq));
  }
  
  static struct nullb_page *null_alloc_page(gfp_t gfp_flags)
  {
  	struct nullb_page *t_page;
  
  	t_page = kmalloc(sizeof(struct nullb_page), gfp_flags);
  	if (!t_page)
  		goto out;
  
  	t_page->page = alloc_pages(gfp_flags, 0);
  	if (!t_page->page)
  		goto out_freepage;
  
  	memset(t_page->bitmap, 0, sizeof(t_page->bitmap));
  	return t_page;
  out_freepage:
  	kfree(t_page);
  out:
  	return NULL;
  }
  
  static void null_free_page(struct nullb_page *t_page)
  {
  	__set_bit(NULLB_PAGE_FREE, t_page->bitmap);
  	if (test_bit(NULLB_PAGE_LOCK, t_page->bitmap))
  		return;
  	__free_page(t_page->page);
  	kfree(t_page);
  }
  
  static bool null_page_empty(struct nullb_page *page)
  {
  	int size = MAP_SZ - 2;
  
  	return find_first_bit(page->bitmap, size) == size;
  }
  
  static void null_free_sector(struct nullb *nullb, sector_t sector,
  	bool is_cache)
  {
  	unsigned int sector_bit;
  	u64 idx;
  	struct nullb_page *t_page, *ret;
  	struct radix_tree_root *root;
  
  	root = is_cache ? &nullb->dev->cache : &nullb->dev->data;
  	idx = sector >> PAGE_SECTORS_SHIFT;
  	sector_bit = (sector & SECTOR_MASK);
  
  	t_page = radix_tree_lookup(root, idx);
  	if (t_page) {
  		__clear_bit(sector_bit, t_page->bitmap);
  
  		if (null_page_empty(t_page)) {
  			ret = radix_tree_delete_item(root, idx, t_page);
  			WARN_ON(ret != t_page);
  			null_free_page(ret);
  			if (is_cache)
  				nullb->dev->curr_cache -= PAGE_SIZE;
  		}
  	}
  }
  
  static struct nullb_page *null_radix_tree_insert(struct nullb *nullb, u64 idx,
  	struct nullb_page *t_page, bool is_cache)
  {
  	struct radix_tree_root *root;
  
  	root = is_cache ? &nullb->dev->cache : &nullb->dev->data;
  
  	if (radix_tree_insert(root, idx, t_page)) {
  		null_free_page(t_page);
  		t_page = radix_tree_lookup(root, idx);
  		WARN_ON(!t_page || t_page->page->index != idx);
  	} else if (is_cache)
  		nullb->dev->curr_cache += PAGE_SIZE;
  
  	return t_page;
  }
  
  static void null_free_device_storage(struct nullb_device *dev, bool is_cache)
  {
  	unsigned long pos = 0;
  	int nr_pages;
  	struct nullb_page *ret, *t_pages[FREE_BATCH];
  	struct radix_tree_root *root;
  
  	root = is_cache ? &dev->cache : &dev->data;
  
  	do {
  		int i;
  
  		nr_pages = radix_tree_gang_lookup(root,
  				(void **)t_pages, pos, FREE_BATCH);
  
  		for (i = 0; i < nr_pages; i++) {
  			pos = t_pages[i]->page->index;
  			ret = radix_tree_delete_item(root, pos, t_pages[i]);
  			WARN_ON(ret != t_pages[i]);
  			null_free_page(ret);
  		}
  
  		pos++;
  	} while (nr_pages == FREE_BATCH);
  
  	if (is_cache)
  		dev->curr_cache = 0;
  }
  
  static struct nullb_page *__null_lookup_page(struct nullb *nullb,
  	sector_t sector, bool for_write, bool is_cache)
  {
  	unsigned int sector_bit;
  	u64 idx;
  	struct nullb_page *t_page;
  	struct radix_tree_root *root;
  
  	idx = sector >> PAGE_SECTORS_SHIFT;
  	sector_bit = (sector & SECTOR_MASK);
  
  	root = is_cache ? &nullb->dev->cache : &nullb->dev->data;
  	t_page = radix_tree_lookup(root, idx);
  	WARN_ON(t_page && t_page->page->index != idx);
  
  	if (t_page && (for_write || test_bit(sector_bit, t_page->bitmap)))
  		return t_page;
  
  	return NULL;
  }
  
  static struct nullb_page *null_lookup_page(struct nullb *nullb,
  	sector_t sector, bool for_write, bool ignore_cache)
  {
  	struct nullb_page *page = NULL;
  
  	if (!ignore_cache)
  		page = __null_lookup_page(nullb, sector, for_write, true);
  	if (page)
  		return page;
  	return __null_lookup_page(nullb, sector, for_write, false);
  }
  
  static struct nullb_page *null_insert_page(struct nullb *nullb,
  					   sector_t sector, bool ignore_cache)
  	__releases(&nullb->lock)
  	__acquires(&nullb->lock)
  {
  	u64 idx;
  	struct nullb_page *t_page;
  
  	t_page = null_lookup_page(nullb, sector, true, ignore_cache);
  	if (t_page)
  		return t_page;
  
  	spin_unlock_irq(&nullb->lock);
  
  	t_page = null_alloc_page(GFP_NOIO);
  	if (!t_page)
  		goto out_lock;
  
  	if (radix_tree_preload(GFP_NOIO))
  		goto out_freepage;
  
  	spin_lock_irq(&nullb->lock);
  	idx = sector >> PAGE_SECTORS_SHIFT;
  	t_page->page->index = idx;
  	t_page = null_radix_tree_insert(nullb, idx, t_page, !ignore_cache);
  	radix_tree_preload_end();
  
  	return t_page;
  out_freepage:
  	null_free_page(t_page);
  out_lock:
  	spin_lock_irq(&nullb->lock);
  	return null_lookup_page(nullb, sector, true, ignore_cache);
  }
  
  static int null_flush_cache_page(struct nullb *nullb, struct nullb_page *c_page)
  {
  	int i;
  	unsigned int offset;
  	u64 idx;
  	struct nullb_page *t_page, *ret;
  	void *dst, *src;
  
  	idx = c_page->page->index;
  
  	t_page = null_insert_page(nullb, idx << PAGE_SECTORS_SHIFT, true);
  
  	__clear_bit(NULLB_PAGE_LOCK, c_page->bitmap);
  	if (test_bit(NULLB_PAGE_FREE, c_page->bitmap)) {
  		null_free_page(c_page);
  		if (t_page && null_page_empty(t_page)) {
  			ret = radix_tree_delete_item(&nullb->dev->data,
  				idx, t_page);
  			null_free_page(t_page);
  		}
  		return 0;
  	}
  
  	if (!t_page)
  		return -ENOMEM;
  
  	src = kmap_atomic(c_page->page);
  	dst = kmap_atomic(t_page->page);
  
  	for (i = 0; i < PAGE_SECTORS;
  			i += (nullb->dev->blocksize >> SECTOR_SHIFT)) {
  		if (test_bit(i, c_page->bitmap)) {
  			offset = (i << SECTOR_SHIFT);
  			memcpy(dst + offset, src + offset,
  				nullb->dev->blocksize);
  			__set_bit(i, t_page->bitmap);
  		}
  	}
  
  	kunmap_atomic(dst);
  	kunmap_atomic(src);
  
  	ret = radix_tree_delete_item(&nullb->dev->cache, idx, c_page);
  	null_free_page(ret);
  	nullb->dev->curr_cache -= PAGE_SIZE;
  
  	return 0;
  }
  
  static int null_make_cache_space(struct nullb *nullb, unsigned long n)
  {
  	int i, err, nr_pages;
  	struct nullb_page *c_pages[FREE_BATCH];
  	unsigned long flushed = 0, one_round;
  
  again:
  	if ((nullb->dev->cache_size * 1024 * 1024) >
  	     nullb->dev->curr_cache + n || nullb->dev->curr_cache == 0)
  		return 0;
  
  	nr_pages = radix_tree_gang_lookup(&nullb->dev->cache,
  			(void **)c_pages, nullb->cache_flush_pos, FREE_BATCH);
  	/*
  	 * nullb_flush_cache_page could unlock before using the c_pages. To
  	 * avoid race, we don't allow page free
  	 */
  	for (i = 0; i < nr_pages; i++) {
  		nullb->cache_flush_pos = c_pages[i]->page->index;
  		/*
  		 * We found the page which is being flushed to disk by other
  		 * threads
  		 */
  		if (test_bit(NULLB_PAGE_LOCK, c_pages[i]->bitmap))
  			c_pages[i] = NULL;
  		else
  			__set_bit(NULLB_PAGE_LOCK, c_pages[i]->bitmap);
  	}
  
  	one_round = 0;
  	for (i = 0; i < nr_pages; i++) {
  		if (c_pages[i] == NULL)
  			continue;
  		err = null_flush_cache_page(nullb, c_pages[i]);
  		if (err)
  			return err;
  		one_round++;
  	}
  	flushed += one_round << PAGE_SHIFT;
  
  	if (n > flushed) {
  		if (nr_pages == 0)
  			nullb->cache_flush_pos = 0;
  		if (one_round == 0) {
  			/* give other threads a chance */
  			spin_unlock_irq(&nullb->lock);
  			spin_lock_irq(&nullb->lock);
  		}
  		goto again;
  	}
  	return 0;
  }
  
  static int copy_to_nullb(struct nullb *nullb, struct page *source,
  	unsigned int off, sector_t sector, size_t n, bool is_fua)
  {
  	size_t temp, count = 0;
  	unsigned int offset;
  	struct nullb_page *t_page;
  	void *dst, *src;
  
  	while (count < n) {
  		temp = min_t(size_t, nullb->dev->blocksize, n - count);
  
  		if (null_cache_active(nullb) && !is_fua)
  			null_make_cache_space(nullb, PAGE_SIZE);
  
  		offset = (sector & SECTOR_MASK) << SECTOR_SHIFT;
  		t_page = null_insert_page(nullb, sector,
  			!null_cache_active(nullb) || is_fua);
  		if (!t_page)
  			return -ENOSPC;
  
  		src = kmap_atomic(source);
  		dst = kmap_atomic(t_page->page);
  		memcpy(dst + offset, src + off + count, temp);
  		kunmap_atomic(dst);
  		kunmap_atomic(src);
  
  		__set_bit(sector & SECTOR_MASK, t_page->bitmap);
  
  		if (is_fua)
  			null_free_sector(nullb, sector, true);
  
  		count += temp;
  		sector += temp >> SECTOR_SHIFT;
  	}
  	return 0;
  }
  
  static int copy_from_nullb(struct nullb *nullb, struct page *dest,
  	unsigned int off, sector_t sector, size_t n)
  {
  	size_t temp, count = 0;
  	unsigned int offset;
  	struct nullb_page *t_page;
  	void *dst, *src;
  
  	while (count < n) {
  		temp = min_t(size_t, nullb->dev->blocksize, n - count);
  
  		offset = (sector & SECTOR_MASK) << SECTOR_SHIFT;
  		t_page = null_lookup_page(nullb, sector, false,
  			!null_cache_active(nullb));
  
  		dst = kmap_atomic(dest);
  		if (!t_page) {
  			memset(dst + off + count, 0, temp);
  			goto next;
  		}
  		src = kmap_atomic(t_page->page);
  		memcpy(dst + off + count, src + offset, temp);
  		kunmap_atomic(src);
  next:
  		kunmap_atomic(dst);
  
  		count += temp;
  		sector += temp >> SECTOR_SHIFT;
  	}
  	return 0;
  }
  
  static void null_handle_discard(struct nullb *nullb, sector_t sector, size_t n)
  {
  	size_t temp;
  
  	spin_lock_irq(&nullb->lock);
  	while (n > 0) {
  		temp = min_t(size_t, n, nullb->dev->blocksize);
  		null_free_sector(nullb, sector, false);
  		if (null_cache_active(nullb))
  			null_free_sector(nullb, sector, true);
  		sector += temp >> SECTOR_SHIFT;
  		n -= temp;
  	}
  	spin_unlock_irq(&nullb->lock);
  }
  
  static int null_handle_flush(struct nullb *nullb)
  {
  	int err;
  
  	if (!null_cache_active(nullb))
  		return 0;
  
  	spin_lock_irq(&nullb->lock);
  	while (true) {
  		err = null_make_cache_space(nullb,
  			nullb->dev->cache_size * 1024 * 1024);
  		if (err || nullb->dev->curr_cache == 0)
  			break;
  	}
  
  	WARN_ON(!radix_tree_empty(&nullb->dev->cache));
  	spin_unlock_irq(&nullb->lock);
  	return err;
  }
  
  static int null_transfer(struct nullb *nullb, struct page *page,
  	unsigned int len, unsigned int off, bool is_write, sector_t sector,
  	bool is_fua)
  {
  	int err = 0;
  
  	if (!is_write) {
  		err = copy_from_nullb(nullb, page, off, sector, len);
  		flush_dcache_page(page);
  	} else {
  		flush_dcache_page(page);
  		err = copy_to_nullb(nullb, page, off, sector, len, is_fua);
  	}
  
  	return err;
  }
  
  static int null_handle_rq(struct nullb_cmd *cmd)
  {
  	struct request *rq = cmd->rq;
  	struct nullb *nullb = cmd->nq->dev->nullb;
  	int err;
  	unsigned int len;
  	sector_t sector;
  	struct req_iterator iter;
  	struct bio_vec bvec;
  
  	sector = blk_rq_pos(rq);
  
  	if (req_op(rq) == REQ_OP_DISCARD) {
  		null_handle_discard(nullb, sector, blk_rq_bytes(rq));
  		return 0;
  	}
  
  	spin_lock_irq(&nullb->lock);
  	rq_for_each_segment(bvec, rq, iter) {
  		len = bvec.bv_len;
  		err = null_transfer(nullb, bvec.bv_page, len, bvec.bv_offset,
  				     op_is_write(req_op(rq)), sector,
  				     req_op(rq) & REQ_FUA);
  		if (err) {
  			spin_unlock_irq(&nullb->lock);
  			return err;
  		}
  		sector += len >> SECTOR_SHIFT;
  	}
  	spin_unlock_irq(&nullb->lock);
  
  	return 0;
  }
  
  static int null_handle_bio(struct nullb_cmd *cmd)
  {
  	struct bio *bio = cmd->bio;
  	struct nullb *nullb = cmd->nq->dev->nullb;
  	int err;
  	unsigned int len;
  	sector_t sector;
  	struct bio_vec bvec;
  	struct bvec_iter iter;
  
  	sector = bio->bi_iter.bi_sector;
  
  	if (bio_op(bio) == REQ_OP_DISCARD) {
  		null_handle_discard(nullb, sector,
  			bio_sectors(bio) << SECTOR_SHIFT);
  		return 0;
  	}
  
  	spin_lock_irq(&nullb->lock);
  	bio_for_each_segment(bvec, bio, iter) {
  		len = bvec.bv_len;
  		err = null_transfer(nullb, bvec.bv_page, len, bvec.bv_offset,
  				     op_is_write(bio_op(bio)), sector,
  				     bio->bi_opf & REQ_FUA);
  		if (err) {
  			spin_unlock_irq(&nullb->lock);
  			return err;
  		}
  		sector += len >> SECTOR_SHIFT;
  	}
  	spin_unlock_irq(&nullb->lock);
  	return 0;
  }
  
  static void null_stop_queue(struct nullb *nullb)
  {
  	struct request_queue *q = nullb->q;
  
  	if (nullb->dev->queue_mode == NULL_Q_MQ)
  		blk_mq_stop_hw_queues(q);
  }
  
  static void null_restart_queue_async(struct nullb *nullb)
  {
  	struct request_queue *q = nullb->q;
  
  	if (nullb->dev->queue_mode == NULL_Q_MQ)
  		blk_mq_start_stopped_hw_queues(q, true);
  }
  
  static blk_status_t null_handle_cmd(struct nullb_cmd *cmd)
  {
  	struct nullb_device *dev = cmd->nq->dev;
  	struct nullb *nullb = dev->nullb;
  	int err = 0;
  
  	if (test_bit(NULLB_DEV_FL_THROTTLED, &dev->flags)) {
  		struct request *rq = cmd->rq;
  
  		if (!hrtimer_active(&nullb->bw_timer))
  			hrtimer_restart(&nullb->bw_timer);
  
  		if (atomic_long_sub_return(blk_rq_bytes(rq),
  				&nullb->cur_bytes) < 0) {
  			null_stop_queue(nullb);
  			/* race with timer */
  			if (atomic_long_read(&nullb->cur_bytes) > 0)
  				null_restart_queue_async(nullb);
  			/* requeue request */
  			return BLK_STS_DEV_RESOURCE;
  		}
  	}
  
  	if (nullb->dev->badblocks.shift != -1) {
  		int bad_sectors;
  		sector_t sector, size, first_bad;
  		bool is_flush = true;
  
  		if (dev->queue_mode == NULL_Q_BIO &&
  				bio_op(cmd->bio) != REQ_OP_FLUSH) {
  			is_flush = false;
  			sector = cmd->bio->bi_iter.bi_sector;
  			size = bio_sectors(cmd->bio);
  		}
  		if (dev->queue_mode != NULL_Q_BIO &&
  				req_op(cmd->rq) != REQ_OP_FLUSH) {
  			is_flush = false;
  			sector = blk_rq_pos(cmd->rq);
  			size = blk_rq_sectors(cmd->rq);
  		}
  		if (!is_flush && badblocks_check(&nullb->dev->badblocks, sector,
  				size, &first_bad, &bad_sectors)) {
  			cmd->error = BLK_STS_IOERR;
  			goto out;
  		}
  	}
  
  	if (dev->memory_backed) {
  		if (dev->queue_mode == NULL_Q_BIO) {
  			if (bio_op(cmd->bio) == REQ_OP_FLUSH)
  				err = null_handle_flush(nullb);
  			else
  				err = null_handle_bio(cmd);
  		} else {
  			if (req_op(cmd->rq) == REQ_OP_FLUSH)
  				err = null_handle_flush(nullb);
  			else
  				err = null_handle_rq(cmd);
  		}
  	}
  	cmd->error = errno_to_blk_status(err);
  
  	if (!cmd->error && dev->zoned) {
  		sector_t sector;
  		unsigned int nr_sectors;
  		int op;
  
  		if (dev->queue_mode == NULL_Q_BIO) {
  			op = bio_op(cmd->bio);
  			sector = cmd->bio->bi_iter.bi_sector;
  			nr_sectors = cmd->bio->bi_iter.bi_size >> 9;
  		} else {
  			op = req_op(cmd->rq);
  			sector = blk_rq_pos(cmd->rq);
  			nr_sectors = blk_rq_sectors(cmd->rq);
  		}
  
  		if (op == REQ_OP_WRITE)
  			null_zone_write(cmd, sector, nr_sectors);
  		else if (op == REQ_OP_ZONE_RESET)
  			null_zone_reset(cmd, sector);
  	}
  out:
  	/* Complete IO by inline, softirq or timer */
  	switch (dev->irqmode) {
  	case NULL_IRQ_SOFTIRQ:
  		switch (dev->queue_mode)  {
  		case NULL_Q_MQ:
  			blk_mq_complete_request(cmd->rq);
  			break;
  		case NULL_Q_BIO:
  			/*
  			 * XXX: no proper submitting cpu information available.
  			 */
  			end_cmd(cmd);
  			break;
  		}
  		break;
  	case NULL_IRQ_NONE:
  		end_cmd(cmd);
  		break;
  	case NULL_IRQ_TIMER:
  		null_cmd_end_timer(cmd);
  		break;
  	}
  	return BLK_STS_OK;
  }
  
  static enum hrtimer_restart nullb_bwtimer_fn(struct hrtimer *timer)
  {
  	struct nullb *nullb = container_of(timer, struct nullb, bw_timer);
  	ktime_t timer_interval = ktime_set(0, TIMER_INTERVAL);
  	unsigned int mbps = nullb->dev->mbps;
  
  	if (atomic_long_read(&nullb->cur_bytes) == mb_per_tick(mbps))
  		return HRTIMER_NORESTART;
  
  	atomic_long_set(&nullb->cur_bytes, mb_per_tick(mbps));
  	null_restart_queue_async(nullb);
  
  	hrtimer_forward_now(&nullb->bw_timer, timer_interval);
  
  	return HRTIMER_RESTART;
  }
  
  static void nullb_setup_bwtimer(struct nullb *nullb)
  {
  	ktime_t timer_interval = ktime_set(0, TIMER_INTERVAL);
  
  	hrtimer_init(&nullb->bw_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
  	nullb->bw_timer.function = nullb_bwtimer_fn;
  	atomic_long_set(&nullb->cur_bytes, mb_per_tick(nullb->dev->mbps));
  	hrtimer_start(&nullb->bw_timer, timer_interval, HRTIMER_MODE_REL);
  }
  
  static struct nullb_queue *nullb_to_queue(struct nullb *nullb)
  {
  	int index = 0;
  
  	if (nullb->nr_queues != 1)
  		index = raw_smp_processor_id() / ((nr_cpu_ids + nullb->nr_queues - 1) / nullb->nr_queues);
  
  	return &nullb->queues[index];
  }
  
  static blk_qc_t null_queue_bio(struct request_queue *q, struct bio *bio)
  {
  	struct nullb *nullb = q->queuedata;
  	struct nullb_queue *nq = nullb_to_queue(nullb);
  	struct nullb_cmd *cmd;
  
  	cmd = alloc_cmd(nq, 1);
  	cmd->bio = bio;
  
  	null_handle_cmd(cmd);
  	return BLK_QC_T_NONE;
  }
  
  static bool should_timeout_request(struct request *rq)
  {
  #ifdef CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION
  	if (g_timeout_str[0])
  		return should_fail(&null_timeout_attr, 1);
  #endif
  	return false;
  }
  
  static bool should_requeue_request(struct request *rq)
  {
  #ifdef CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION
  	if (g_requeue_str[0])
  		return should_fail(&null_requeue_attr, 1);
  #endif
  	return false;
  }
  
  static enum blk_eh_timer_return null_timeout_rq(struct request *rq, bool res)
  {
  	pr_info("null: rq %p timed out\n", rq);
  	blk_mq_complete_request(rq);
  	return BLK_EH_DONE;
  }
  
  static blk_status_t null_queue_rq(struct blk_mq_hw_ctx *hctx,
  			 const struct blk_mq_queue_data *bd)
  {
  	struct nullb_cmd *cmd = blk_mq_rq_to_pdu(bd->rq);
  	struct nullb_queue *nq = hctx->driver_data;
  
  	might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);
  
  	if (nq->dev->irqmode == NULL_IRQ_TIMER) {
  		hrtimer_init(&cmd->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
  		cmd->timer.function = null_cmd_timer_expired;
  	}
  	cmd->rq = bd->rq;
  	cmd->nq = nq;
  
  	blk_mq_start_request(bd->rq);
  
  	if (should_requeue_request(bd->rq)) {
  		/*
  		 * Alternate between hitting the core BUSY path, and the
  		 * driver driven requeue path
  		 */
  		nq->requeue_selection++;
  		if (nq->requeue_selection & 1)
  			return BLK_STS_RESOURCE;
  		else {
  			blk_mq_requeue_request(bd->rq, true);
  			return BLK_STS_OK;
  		}
  	}
  	if (should_timeout_request(bd->rq))
  		return BLK_STS_OK;
  
  	return null_handle_cmd(cmd);
  }
  
  static const struct blk_mq_ops null_mq_ops = {
  	.queue_rq       = null_queue_rq,
  	.complete	= null_complete_rq,
  	.timeout	= null_timeout_rq,
  };
  
  static void cleanup_queue(struct nullb_queue *nq)
  {
  	kfree(nq->tag_map);
  	kfree(nq->cmds);
  }
  
  static void cleanup_queues(struct nullb *nullb)
  {
  	int i;
  
  	for (i = 0; i < nullb->nr_queues; i++)
  		cleanup_queue(&nullb->queues[i]);
  
  	kfree(nullb->queues);
  }
  
  static void null_del_dev(struct nullb *nullb)
  {
  	struct nullb_device *dev = nullb->dev;
  
  	ida_simple_remove(&nullb_indexes, nullb->index);
  
  	list_del_init(&nullb->list);
  
  	del_gendisk(nullb->disk);
  
  	if (test_bit(NULLB_DEV_FL_THROTTLED, &nullb->dev->flags)) {
  		hrtimer_cancel(&nullb->bw_timer);
  		atomic_long_set(&nullb->cur_bytes, LONG_MAX);
  		null_restart_queue_async(nullb);
  	}
  
  	blk_cleanup_queue(nullb->q);
  	if (dev->queue_mode == NULL_Q_MQ &&
  	    nullb->tag_set == &nullb->__tag_set)
  		blk_mq_free_tag_set(nullb->tag_set);
  	put_disk(nullb->disk);
  	cleanup_queues(nullb);
  	if (null_cache_active(nullb))
  		null_free_device_storage(nullb->dev, true);
  	kfree(nullb);
  	dev->nullb = NULL;
  }
  
  static void null_config_discard(struct nullb *nullb)
  {
  	if (nullb->dev->discard == false)
  		return;
  	nullb->q->limits.discard_granularity = nullb->dev->blocksize;
  	nullb->q->limits.discard_alignment = nullb->dev->blocksize;
  	blk_queue_max_discard_sectors(nullb->q, UINT_MAX >> 9);
  	blk_queue_flag_set(QUEUE_FLAG_DISCARD, nullb->q);
  }
  
  static int null_open(struct block_device *bdev, fmode_t mode)
  {
  	return 0;
  }
  
  static void null_release(struct gendisk *disk, fmode_t mode)
  {
  }
  
  static const struct block_device_operations null_fops = {
  	.owner =	THIS_MODULE,
  	.open =		null_open,
  	.release =	null_release,
  	.report_zones =	null_zone_report,
  };
  
  static void null_init_queue(struct nullb *nullb, struct nullb_queue *nq)
  {
  	BUG_ON(!nullb);
  	BUG_ON(!nq);
  
  	init_waitqueue_head(&nq->wait);
  	nq->queue_depth = nullb->queue_depth;
  	nq->dev = nullb->dev;
  }
  
  static void null_init_queues(struct nullb *nullb)
  {
  	struct request_queue *q = nullb->q;
  	struct blk_mq_hw_ctx *hctx;
  	struct nullb_queue *nq;
  	int i;
  
  	queue_for_each_hw_ctx(q, hctx, i) {
  		if (!hctx->nr_ctx || !hctx->tags)
  			continue;
  		nq = &nullb->queues[i];
  		hctx->driver_data = nq;
  		null_init_queue(nullb, nq);
  		nullb->nr_queues++;
  	}
  }
  
  static int setup_commands(struct nullb_queue *nq)
  {
  	struct nullb_cmd *cmd;
  	int i, tag_size;
  
  	nq->cmds = kcalloc(nq->queue_depth, sizeof(*cmd), GFP_KERNEL);
  	if (!nq->cmds)
  		return -ENOMEM;
  
  	tag_size = ALIGN(nq->queue_depth, BITS_PER_LONG) / BITS_PER_LONG;
  	nq->tag_map = kcalloc(tag_size, sizeof(unsigned long), GFP_KERNEL);
  	if (!nq->tag_map) {
  		kfree(nq->cmds);
  		return -ENOMEM;
  	}
  
  	for (i = 0; i < nq->queue_depth; i++) {
  		cmd = &nq->cmds[i];
  		INIT_LIST_HEAD(&cmd->list);
  		cmd->ll_list.next = NULL;
  		cmd->tag = -1U;
  	}
  
  	return 0;
  }
  
  static int setup_queues(struct nullb *nullb)
  {
  	nullb->queues = kcalloc(nullb->dev->submit_queues,
  				sizeof(struct nullb_queue),
  				GFP_KERNEL);
  	if (!nullb->queues)
  		return -ENOMEM;
  
  	nullb->nr_queues = 0;
  	nullb->queue_depth = nullb->dev->hw_queue_depth;
  
  	return 0;
  }
  
  static int init_driver_queues(struct nullb *nullb)
  {
  	struct nullb_queue *nq;
  	int i, ret = 0;
  
  	for (i = 0; i < nullb->dev->submit_queues; i++) {
  		nq = &nullb->queues[i];
  
  		null_init_queue(nullb, nq);
  
  		ret = setup_commands(nq);
  		if (ret)
  			return ret;
  		nullb->nr_queues++;
  	}
  	return 0;
  }
  
  static int null_gendisk_register(struct nullb *nullb)
  {
  	struct gendisk *disk;
  	sector_t size;
  
  	disk = nullb->disk = alloc_disk_node(1, nullb->dev->home_node);
  	if (!disk)
  		return -ENOMEM;
  	size = (sector_t)nullb->dev->size * 1024 * 1024ULL;
  	set_capacity(disk, size >> 9);
  
  	disk->flags |= GENHD_FL_EXT_DEVT | GENHD_FL_SUPPRESS_PARTITION_INFO;
  	disk->major		= null_major;
  	disk->first_minor	= nullb->index;
  	disk->fops		= &null_fops;
  	disk->private_data	= nullb;
  	disk->queue		= nullb->q;
  	strncpy(disk->disk_name, nullb->disk_name, DISK_NAME_LEN);
  
  	if (nullb->dev->zoned) {
  		int ret = blk_revalidate_disk_zones(disk);
  
  		if (ret != 0)
  			return ret;
  	}
  
  	add_disk(disk);
  	return 0;
  }
  
  static int null_init_tag_set(struct nullb *nullb, struct blk_mq_tag_set *set)
  {
  	set->ops = &null_mq_ops;
  	set->nr_hw_queues = nullb ? nullb->dev->submit_queues :
  						g_submit_queues;
  	set->queue_depth = nullb ? nullb->dev->hw_queue_depth :
  						g_hw_queue_depth;
  	set->numa_node = nullb ? nullb->dev->home_node : g_home_node;
  	set->cmd_size	= sizeof(struct nullb_cmd);
  	set->flags = BLK_MQ_F_SHOULD_MERGE;
  	if (g_no_sched)
  		set->flags |= BLK_MQ_F_NO_SCHED;
  	set->driver_data = NULL;
  
  	if ((nullb && nullb->dev->blocking) || g_blocking)
  		set->flags |= BLK_MQ_F_BLOCKING;
  
  	return blk_mq_alloc_tag_set(set);
  }
  
  static void null_validate_conf(struct nullb_device *dev)
  {
  	dev->blocksize = round_down(dev->blocksize, 512);
  	dev->blocksize = clamp_t(unsigned int, dev->blocksize, 512, 4096);
  
  	if (dev->queue_mode == NULL_Q_MQ && dev->use_per_node_hctx) {
  		if (dev->submit_queues != nr_online_nodes)
  			dev->submit_queues = nr_online_nodes;
  	} else if (dev->submit_queues > nr_cpu_ids)
  		dev->submit_queues = nr_cpu_ids;
  	else if (dev->submit_queues == 0)
  		dev->submit_queues = 1;
  
  	dev->queue_mode = min_t(unsigned int, dev->queue_mode, NULL_Q_MQ);
  	dev->irqmode = min_t(unsigned int, dev->irqmode, NULL_IRQ_TIMER);
  
  	/* Do memory allocation, so set blocking */
  	if (dev->memory_backed)
  		dev->blocking = true;
  	else /* cache is meaningless */
  		dev->cache_size = 0;
  	dev->cache_size = min_t(unsigned long, ULONG_MAX / 1024 / 1024,
  						dev->cache_size);
  	dev->mbps = min_t(unsigned int, 1024 * 40, dev->mbps);
  	/* can not stop a queue */
  	if (dev->queue_mode == NULL_Q_BIO)
  		dev->mbps = 0;
  }
  
  #ifdef CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION
  static bool __null_setup_fault(struct fault_attr *attr, char *str)
  {
  	if (!str[0])
  		return true;
  
  	if (!setup_fault_attr(attr, str))
  		return false;
  
  	attr->verbose = 0;
  	return true;
  }
  #endif
  
  static bool null_setup_fault(void)
  {
  #ifdef CONFIG_BLK_DEV_NULL_BLK_FAULT_INJECTION
  	if (!__null_setup_fault(&null_timeout_attr, g_timeout_str))
  		return false;
  	if (!__null_setup_fault(&null_requeue_attr, g_requeue_str))
  		return false;
  #endif
  	return true;
  }
  
  static int null_add_dev(struct nullb_device *dev)
  {
  	struct nullb *nullb;
  	int rv;
  
  	null_validate_conf(dev);
  
  	nullb = kzalloc_node(sizeof(*nullb), GFP_KERNEL, dev->home_node);
  	if (!nullb) {
  		rv = -ENOMEM;
  		goto out;
  	}
  	nullb->dev = dev;
  	dev->nullb = nullb;
  
  	spin_lock_init(&nullb->lock);
  
  	rv = setup_queues(nullb);
  	if (rv)
  		goto out_free_nullb;
  
  	if (dev->queue_mode == NULL_Q_MQ) {
  		if (shared_tags) {
  			nullb->tag_set = &tag_set;
  			rv = 0;
  		} else {
  			nullb->tag_set = &nullb->__tag_set;
  			rv = null_init_tag_set(nullb, nullb->tag_set);
  		}
  
  		if (rv)
  			goto out_cleanup_queues;
  
  		if (!null_setup_fault())
  			goto out_cleanup_queues;
  
  		nullb->tag_set->timeout = 5 * HZ;
  		nullb->q = blk_mq_init_queue(nullb->tag_set);
  		if (IS_ERR(nullb->q)) {
  			rv = -ENOMEM;
  			goto out_cleanup_tags;
  		}
  		null_init_queues(nullb);
  	} else if (dev->queue_mode == NULL_Q_BIO) {
  		nullb->q = blk_alloc_queue_node(GFP_KERNEL, dev->home_node);
  		if (!nullb->q) {
  			rv = -ENOMEM;
  			goto out_cleanup_queues;
  		}
  		blk_queue_make_request(nullb->q, null_queue_bio);
  		rv = init_driver_queues(nullb);
  		if (rv)
  			goto out_cleanup_blk_queue;
  	}
  
  	if (dev->mbps) {
  		set_bit(NULLB_DEV_FL_THROTTLED, &dev->flags);
  		nullb_setup_bwtimer(nullb);
  	}
  
  	if (dev->cache_size > 0) {
  		set_bit(NULLB_DEV_FL_CACHE, &nullb->dev->flags);
  		blk_queue_write_cache(nullb->q, true, true);
  	}
  
  	if (dev->zoned) {
  		rv = null_zone_init(dev);
  		if (rv)
  			goto out_cleanup_blk_queue;
  
  		blk_queue_chunk_sectors(nullb->q, dev->zone_size_sects);
  		nullb->q->limits.zoned = BLK_ZONED_HM;
  	}
  
  	nullb->q->queuedata = nullb;
  	blk_queue_flag_set(QUEUE_FLAG_NONROT, nullb->q);
  	blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, nullb->q);
  
  	mutex_lock(&lock);
  	nullb->index = ida_simple_get(&nullb_indexes, 0, 0, GFP_KERNEL);
  	dev->index = nullb->index;
  	mutex_unlock(&lock);
  
  	blk_queue_logical_block_size(nullb->q, dev->blocksize);
  	blk_queue_physical_block_size(nullb->q, dev->blocksize);
  
  	null_config_discard(nullb);
  
  	sprintf(nullb->disk_name, "nullb%d", nullb->index);
  
  	rv = null_gendisk_register(nullb);
  	if (rv)
  		goto out_cleanup_zone;
  
  	mutex_lock(&lock);
  	list_add_tail(&nullb->list, &nullb_list);
  	mutex_unlock(&lock);
  
  	return 0;
  out_cleanup_zone:
  	if (dev->zoned)
  		null_zone_exit(dev);
  out_cleanup_blk_queue:
  	blk_cleanup_queue(nullb->q);
  out_cleanup_tags:
  	if (dev->queue_mode == NULL_Q_MQ && nullb->tag_set == &nullb->__tag_set)
  		blk_mq_free_tag_set(nullb->tag_set);
  out_cleanup_queues:
  	cleanup_queues(nullb);
  out_free_nullb:
  	kfree(nullb);
  out:
  	return rv;
  }
  
  static int __init null_init(void)
  {
  	int ret = 0;
  	unsigned int i;
  	struct nullb *nullb;
  	struct nullb_device *dev;
  
  	if (g_bs > PAGE_SIZE) {
  		pr_warn("null_blk: invalid block size\n");
  		pr_warn("null_blk: defaults block size to %lu\n", PAGE_SIZE);
  		g_bs = PAGE_SIZE;
  	}
  
  	if (!is_power_of_2(g_zone_size)) {
  		pr_err("null_blk: zone_size must be power-of-two\n");
  		return -EINVAL;
  	}
  
  	if (g_home_node != NUMA_NO_NODE && g_home_node >= nr_online_nodes) {
  		pr_err("null_blk: invalid home_node value\n");
  		g_home_node = NUMA_NO_NODE;
  	}
  
  	if (g_queue_mode == NULL_Q_RQ) {
  		pr_err("null_blk: legacy IO path no longer available\n");
  		return -EINVAL;
  	}
  	if (g_queue_mode == NULL_Q_MQ && g_use_per_node_hctx) {
  		if (g_submit_queues != nr_online_nodes) {
  			pr_warn("null_blk: submit_queues param is set to %u.\n",
  							nr_online_nodes);
  			g_submit_queues = nr_online_nodes;
  		}
  	} else if (g_submit_queues > nr_cpu_ids)
  		g_submit_queues = nr_cpu_ids;
  	else if (g_submit_queues <= 0)
  		g_submit_queues = 1;
  
  	if (g_queue_mode == NULL_Q_MQ && shared_tags) {
  		ret = null_init_tag_set(NULL, &tag_set);
  		if (ret)
  			return ret;
  	}
  
  	config_group_init(&nullb_subsys.su_group);
  	mutex_init(&nullb_subsys.su_mutex);
  
  	ret = configfs_register_subsystem(&nullb_subsys);
  	if (ret)
  		goto err_tagset;
  
  	mutex_init(&lock);
  
  	null_major = register_blkdev(0, "nullb");
  	if (null_major < 0) {
  		ret = null_major;
  		goto err_conf;
  	}
  
  	for (i = 0; i < nr_devices; i++) {
  		dev = null_alloc_dev();
  		if (!dev) {
  			ret = -ENOMEM;
  			goto err_dev;
  		}
  		ret = null_add_dev(dev);
  		if (ret) {
  			null_free_dev(dev);
  			goto err_dev;
  		}
  	}
  
  	pr_info("null: module loaded\n");
  	return 0;
  
  err_dev:
  	while (!list_empty(&nullb_list)) {
  		nullb = list_entry(nullb_list.next, struct nullb, list);
  		dev = nullb->dev;
  		null_del_dev(nullb);
  		null_free_dev(dev);
  	}
  	unregister_blkdev(null_major, "nullb");
  err_conf:
  	configfs_unregister_subsystem(&nullb_subsys);
  err_tagset:
  	if (g_queue_mode == NULL_Q_MQ && shared_tags)
  		blk_mq_free_tag_set(&tag_set);
  	return ret;
  }
  
  static void __exit null_exit(void)
  {
  	struct nullb *nullb;
  
  	configfs_unregister_subsystem(&nullb_subsys);
  
  	unregister_blkdev(null_major, "nullb");
  
  	mutex_lock(&lock);
  	while (!list_empty(&nullb_list)) {
  		struct nullb_device *dev;
  
  		nullb = list_entry(nullb_list.next, struct nullb, list);
  		dev = nullb->dev;
  		null_del_dev(nullb);
  		null_free_dev(dev);
  	}
  	mutex_unlock(&lock);
  
  	if (g_queue_mode == NULL_Q_MQ && shared_tags)
  		blk_mq_free_tag_set(&tag_set);
  }
  
  module_init(null_init);
  module_exit(null_exit);
  
  MODULE_AUTHOR("Jens Axboe <axboe@kernel.dk>");
  MODULE_LICENSE("GPL");
  