/*
   * Copyright (C) 2001, 2002 Sistina Software (UK) Limited.

   * Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.

   *
   * This file is released under the GPL.
   */
  
  #include "dm.h"

  #include "dm-uevent.h"

  
  #include <linux/init.h>
  #include <linux/module.h>

  #include <linux/mutex.h>

  #include <linux/moduleparam.h>
  #include <linux/blkpg.h>
  #include <linux/bio.h>
  #include <linux/buffer_head.h>
  #include <linux/mempool.h>
  #include <linux/slab.h>
  #include <linux/idr.h>

  #include <linux/hdreg.h>

  
  #include <trace/events/block.h>

  #define DM_MSG_PREFIX "core"

  /*
   * Cookies are numeric values sent with CHANGE and REMOVE
   * uevents while resuming, removing or renaming the device.
   */
  #define DM_COOKIE_ENV_VAR_NAME "DM_COOKIE"
  #define DM_COOKIE_LENGTH 24

  static const char *_name = DM_NAME;
  
  static unsigned int major = 0;
  static unsigned int _major = 0;

  static DEFINE_SPINLOCK(_minor_lock);

  /*

   * For bio-based dm.

   * One of these is allocated per bio.
   */
  struct dm_io {
  	struct mapped_device *md;
  	int error;

  	atomic_t io_count;

  	struct bio *bio;

  	unsigned long start_time;

  };
  
  /*

   * For bio-based dm.

   * One of these is allocated per target within a bio.  Hopefully
   * this will be simplified out one day.
   */

  struct dm_target_io {

  	struct dm_io *io;
  	struct dm_target *ti;
  	union map_info info;
  };

  /*
   * For request-based dm.
   * One of these is allocated per request.
   */
  struct dm_rq_target_io {
  	struct mapped_device *md;
  	struct dm_target *ti;
  	struct request *orig, clone;
  	int error;
  	union map_info info;
  };
  
  /*
   * For request-based dm.
   * One of these is allocated per bio.
   */
  struct dm_rq_clone_bio_info {
  	struct bio *orig;

  	struct dm_rq_target_io *tio;

  };

  union map_info *dm_get_mapinfo(struct bio *bio)
  {

  	if (bio && bio->bi_private)

  		return &((struct dm_target_io *)bio->bi_private)->info;

  	return NULL;

  }

  union map_info *dm_get_rq_mapinfo(struct request *rq)
  {
  	if (rq && rq->end_io_data)
  		return &((struct dm_rq_target_io *)rq->end_io_data)->info;
  	return NULL;
  }
  EXPORT_SYMBOL_GPL(dm_get_rq_mapinfo);

  #define MINOR_ALLOCED ((void *)-1)

  /*
   * Bits for the md->flags field.
   */

  #define DMF_BLOCK_IO_FOR_SUSPEND 0

  #define DMF_SUSPENDED 1

  #define DMF_FROZEN 2

  #define DMF_FREEING 3

  #define DMF_DELETING 4

  #define DMF_NOFLUSH_SUSPENDING 5

  #define DMF_QUEUE_IO_TO_THREAD 6

  /*
   * Work processed by per-device workqueue.
   */

  struct mapped_device {

  	struct rw_semaphore io_lock;

  	struct mutex suspend_lock;

  	rwlock_t map_lock;
  	atomic_t holders;

  	atomic_t open_count;

  
  	unsigned long flags;

  	struct request_queue *queue;

  	struct gendisk *disk;

  	char name[16];

  
  	void *interface_ptr;
  
  	/*
  	 * A list of ios that arrived while we were suspended.
  	 */
  	atomic_t pending;
  	wait_queue_head_t wait;

  	struct work_struct work;

  	struct bio_list deferred;

  	spinlock_t deferred_lock;

  
  	/*

  	 * An error from the barrier request currently being processed.
  	 */
  	int barrier_error;
  
  	/*

  	 * Processing queue (flush/barriers)
  	 */
  	struct workqueue_struct *wq;
  
  	/*

  	 * The current mapping.
  	 */
  	struct dm_table *map;
  
  	/*
  	 * io objects are allocated from here.
  	 */
  	mempool_t *io_pool;
  	mempool_t *tio_pool;

  	struct bio_set *bs;

  	/*
  	 * Event handling.
  	 */
  	atomic_t event_nr;
  	wait_queue_head_t eventq;

  	atomic_t uevent_seq;
  	struct list_head uevent_list;
  	spinlock_t uevent_lock; /* Protect access to uevent_list */

  
  	/*
  	 * freeze/thaw support require holding onto a super block
  	 */
  	struct super_block *frozen_sb;

  	struct block_device *bdev;

  
  	/* forced geometry settings */
  	struct hd_geometry geometry;

  	/* marker of flush suspend for request-based dm */
  	struct request suspend_rq;
  
  	/* For saving the address of __make_request for request based dm */
  	make_request_fn *saved_make_request_fn;

  	/* sysfs handle */
  	struct kobject kobj;

  
  	/* zero-length barrier that will be cloned and submitted to targets */
  	struct bio barrier_bio;

  };

  /*
   * For mempools pre-allocation at the table loading time.
   */
  struct dm_md_mempools {
  	mempool_t *io_pool;
  	mempool_t *tio_pool;
  	struct bio_set *bs;
  };

  #define MIN_IOS 256

  static struct kmem_cache *_io_cache;
  static struct kmem_cache *_tio_cache;

  static struct kmem_cache *_rq_tio_cache;
  static struct kmem_cache *_rq_bio_info_cache;

  static int __init local_init(void)
  {

  	int r = -ENOMEM;

  	/* allocate a slab for the dm_ios */

  	_io_cache = KMEM_CACHE(dm_io, 0);

  	if (!_io_cache)

  		return r;

  
  	/* allocate a slab for the target ios */

  	_tio_cache = KMEM_CACHE(dm_target_io, 0);

  	if (!_tio_cache)
  		goto out_free_io_cache;

  	_rq_tio_cache = KMEM_CACHE(dm_rq_target_io, 0);
  	if (!_rq_tio_cache)
  		goto out_free_tio_cache;
  
  	_rq_bio_info_cache = KMEM_CACHE(dm_rq_clone_bio_info, 0);
  	if (!_rq_bio_info_cache)
  		goto out_free_rq_tio_cache;

  	r = dm_uevent_init();

  	if (r)

  		goto out_free_rq_bio_info_cache;

  	_major = major;
  	r = register_blkdev(_major, _name);

  	if (r < 0)
  		goto out_uevent_exit;

  
  	if (!_major)
  		_major = r;
  
  	return 0;

  
  out_uevent_exit:
  	dm_uevent_exit();

  out_free_rq_bio_info_cache:
  	kmem_cache_destroy(_rq_bio_info_cache);
  out_free_rq_tio_cache:
  	kmem_cache_destroy(_rq_tio_cache);

  out_free_tio_cache:
  	kmem_cache_destroy(_tio_cache);
  out_free_io_cache:
  	kmem_cache_destroy(_io_cache);
  
  	return r;

  }
  
  static void local_exit(void)
  {

  	kmem_cache_destroy(_rq_bio_info_cache);
  	kmem_cache_destroy(_rq_tio_cache);

  	kmem_cache_destroy(_tio_cache);
  	kmem_cache_destroy(_io_cache);

  	unregister_blkdev(_major, _name);

  	dm_uevent_exit();

  
  	_major = 0;
  
  	DMINFO("cleaned up");
  }

  static int (*_inits[])(void) __initdata = {

  	local_init,
  	dm_target_init,
  	dm_linear_init,
  	dm_stripe_init,

  	dm_kcopyd_init,

  	dm_interface_init,
  };

  static void (*_exits[])(void) = {

  	local_exit,
  	dm_target_exit,
  	dm_linear_exit,
  	dm_stripe_exit,

  	dm_kcopyd_exit,

  	dm_interface_exit,
  };
  
  static int __init dm_init(void)
  {
  	const int count = ARRAY_SIZE(_inits);
  
  	int r, i;
  
  	for (i = 0; i < count; i++) {
  		r = _inits[i]();
  		if (r)
  			goto bad;
  	}
  
  	return 0;
  
        bad:
  	while (i--)
  		_exits[i]();
  
  	return r;
  }
  
  static void __exit dm_exit(void)
  {
  	int i = ARRAY_SIZE(_exits);
  
  	while (i--)
  		_exits[i]();
  }
  
  /*
   * Block device functions
   */

  static int dm_blk_open(struct block_device *bdev, fmode_t mode)

  {
  	struct mapped_device *md;

  	spin_lock(&_minor_lock);

  	md = bdev->bd_disk->private_data;

  	if (!md)
  		goto out;

  	if (test_bit(DMF_FREEING, &md->flags) ||
  	    test_bit(DMF_DELETING, &md->flags)) {

  		md = NULL;
  		goto out;
  	}

  	dm_get(md);

  	atomic_inc(&md->open_count);

  
  out:
  	spin_unlock(&_minor_lock);
  
  	return md ? 0 : -ENXIO;

  }

  static int dm_blk_close(struct gendisk *disk, fmode_t mode)

  {

  	struct mapped_device *md = disk->private_data;

  	atomic_dec(&md->open_count);

  	dm_put(md);
  	return 0;
  }

  int dm_open_count(struct mapped_device *md)
  {
  	return atomic_read(&md->open_count);
  }
  
  /*
   * Guarantees nothing is using the device before it's deleted.
   */
  int dm_lock_for_deletion(struct mapped_device *md)
  {
  	int r = 0;
  
  	spin_lock(&_minor_lock);
  
  	if (dm_open_count(md))
  		r = -EBUSY;
  	else
  		set_bit(DMF_DELETING, &md->flags);
  
  	spin_unlock(&_minor_lock);
  
  	return r;
  }

  static int dm_blk_getgeo(struct block_device *bdev, struct hd_geometry *geo)
  {
  	struct mapped_device *md = bdev->bd_disk->private_data;
  
  	return dm_get_geometry(md, geo);
  }

  static int dm_blk_ioctl(struct block_device *bdev, fmode_t mode,

  			unsigned int cmd, unsigned long arg)
  {

  	struct mapped_device *md = bdev->bd_disk->private_data;
  	struct dm_table *map = dm_get_table(md);

  	struct dm_target *tgt;
  	int r = -ENOTTY;

  	if (!map || !dm_table_get_size(map))
  		goto out;
  
  	/* We only support devices that have a single target */
  	if (dm_table_get_num_targets(map) != 1)
  		goto out;
  
  	tgt = dm_table_get_target(map, 0);
  
  	if (dm_suspended(md)) {
  		r = -EAGAIN;
  		goto out;
  	}
  
  	if (tgt->type->ioctl)

  		r = tgt->type->ioctl(tgt, cmd, arg);

  
  out:
  	dm_table_put(map);

  	return r;
  }

  static struct dm_io *alloc_io(struct mapped_device *md)

  {
  	return mempool_alloc(md->io_pool, GFP_NOIO);
  }

  static void free_io(struct mapped_device *md, struct dm_io *io)

  {
  	mempool_free(io, md->io_pool);
  }

  static void free_tio(struct mapped_device *md, struct dm_target_io *tio)

  {
  	mempool_free(tio, md->tio_pool);
  }

  static struct dm_rq_target_io *alloc_rq_tio(struct mapped_device *md)
  {
  	return mempool_alloc(md->tio_pool, GFP_ATOMIC);
  }
  
  static void free_rq_tio(struct dm_rq_target_io *tio)
  {
  	mempool_free(tio, tio->md->tio_pool);
  }
  
  static struct dm_rq_clone_bio_info *alloc_bio_info(struct mapped_device *md)
  {
  	return mempool_alloc(md->io_pool, GFP_ATOMIC);
  }
  
  static void free_bio_info(struct dm_rq_clone_bio_info *info)
  {
  	mempool_free(info, info->tio->md->io_pool);
  }

  static void start_io_acct(struct dm_io *io)
  {
  	struct mapped_device *md = io->md;

  	int cpu;

  
  	io->start_time = jiffies;

  	cpu = part_stat_lock();
  	part_round_stats(cpu, &dm_disk(md)->part0);
  	part_stat_unlock();
  	dm_disk(md)->part0.in_flight = atomic_inc_return(&md->pending);

  }

  static void end_io_acct(struct dm_io *io)

  {
  	struct mapped_device *md = io->md;
  	struct bio *bio = io->bio;
  	unsigned long duration = jiffies - io->start_time;

  	int pending, cpu;

  	int rw = bio_data_dir(bio);

  	cpu = part_stat_lock();
  	part_round_stats(cpu, &dm_disk(md)->part0);
  	part_stat_add(cpu, &dm_disk(md)->part0, ticks[rw], duration);
  	part_stat_unlock();

  	/*
  	 * After this is decremented the bio must not be touched if it is
  	 * a barrier.
  	 */

  	dm_disk(md)->part0.in_flight = pending =
  		atomic_dec_return(&md->pending);

  	/* nudge anyone waiting on suspend queue */
  	if (!pending)
  		wake_up(&md->wait);

  }

  /*
   * Add the bio to the list of deferred io.
   */

  static void queue_io(struct mapped_device *md, struct bio *bio)

  {

  	down_write(&md->io_lock);

  	spin_lock_irq(&md->deferred_lock);

  	bio_list_add(&md->deferred, bio);

  	spin_unlock_irq(&md->deferred_lock);

  	if (!test_and_set_bit(DMF_QUEUE_IO_TO_THREAD, &md->flags))
  		queue_work(md->wq, &md->work);

  	up_write(&md->io_lock);

  }
  
  /*
   * Everyone (including functions in this file), should use this
   * function to access the md->map field, and make sure they call
   * dm_table_put() when finished.
   */
  struct dm_table *dm_get_table(struct mapped_device *md)
  {
  	struct dm_table *t;

  	unsigned long flags;

  	read_lock_irqsave(&md->map_lock, flags);

  	t = md->map;
  	if (t)
  		dm_table_get(t);

  	read_unlock_irqrestore(&md->map_lock, flags);

  
  	return t;
  }

  /*
   * Get the geometry associated with a dm device
   */
  int dm_get_geometry(struct mapped_device *md, struct hd_geometry *geo)
  {
  	*geo = md->geometry;
  
  	return 0;
  }
  
  /*
   * Set the geometry of a device.
   */
  int dm_set_geometry(struct mapped_device *md, struct hd_geometry *geo)
  {
  	sector_t sz = (sector_t)geo->cylinders * geo->heads * geo->sectors;
  
  	if (geo->start > sz) {
  		DMWARN("Start sector is beyond the geometry limits.");
  		return -EINVAL;
  	}
  
  	md->geometry = *geo;
  
  	return 0;
  }

  /*-----------------------------------------------------------------
   * CRUD START:
   *   A more elegant soln is in the works that uses the queue
   *   merge fn, unfortunately there are a couple of changes to
   *   the block layer that I want to make for this.  So in the
   *   interests of getting something for people to use I give
   *   you this clearly demarcated crap.
   *---------------------------------------------------------------*/

  static int __noflush_suspending(struct mapped_device *md)
  {
  	return test_bit(DMF_NOFLUSH_SUSPENDING, &md->flags);
  }

  /*
   * Decrements the number of outstanding ios that a bio has been
   * cloned into, completing the original io if necc.
   */

  static void dec_pending(struct dm_io *io, int error)

  {

  	unsigned long flags;

  	int io_error;
  	struct bio *bio;
  	struct mapped_device *md = io->md;

  
  	/* Push-back supersedes any I/O errors */

  	if (error && !(io->error > 0 && __noflush_suspending(md)))

  		io->error = error;
  
  	if (atomic_dec_and_test(&io->io_count)) {

  		if (io->error == DM_ENDIO_REQUEUE) {
  			/*
  			 * Target requested pushing back the I/O.

  			 */

  			spin_lock_irqsave(&md->deferred_lock, flags);

  			if (__noflush_suspending(md)) {
  				if (!bio_barrier(io->bio))
  					bio_list_add_head(&md->deferred,
  							  io->bio);
  			} else

  				/* noflush suspend was interrupted. */
  				io->error = -EIO;

  			spin_unlock_irqrestore(&md->deferred_lock, flags);

  		}

  		io_error = io->error;
  		bio = io->bio;

  		if (bio_barrier(bio)) {
  			/*
  			 * There can be just one barrier request so we use
  			 * a per-device variable for error reporting.
  			 * Note that you can't touch the bio after end_io_acct
  			 */

  			if (!md->barrier_error && io_error != -EOPNOTSUPP)

  				md->barrier_error = io_error;

  			end_io_acct(io);
  		} else {
  			end_io_acct(io);

  			if (io_error != DM_ENDIO_REQUEUE) {
  				trace_block_bio_complete(md->queue, bio);

  				bio_endio(bio, io_error);
  			}

  		}

  
  		free_io(md, io);

  	}
  }

  static void clone_endio(struct bio *bio, int error)

  {
  	int r = 0;

  	struct dm_target_io *tio = bio->bi_private;

  	struct dm_io *io = tio->io;

  	struct mapped_device *md = tio->io->md;

  	dm_endio_fn endio = tio->ti->type->end_io;

  	if (!bio_flagged(bio, BIO_UPTODATE) && !error)
  		error = -EIO;
  
  	if (endio) {
  		r = endio(tio->ti, bio, error, &tio->info);

  		if (r < 0 || r == DM_ENDIO_REQUEUE)
  			/*
  			 * error and requeue request are handled
  			 * in dec_pending().
  			 */

  			error = r;

  		else if (r == DM_ENDIO_INCOMPLETE)
  			/* The target will handle the io */

  			return;

  		else if (r) {
  			DMWARN("unimplemented target endio return value: %d", r);
  			BUG();
  		}

  	}

  	/*
  	 * Store md for cleanup instead of tio which is about to get freed.
  	 */
  	bio->bi_private = md->bs;

  	free_tio(md, tio);

  	bio_put(bio);
  	dec_pending(io, error);

  }

  /*
   * Partial completion handling for request-based dm
   */
  static void end_clone_bio(struct bio *clone, int error)
  {
  	struct dm_rq_clone_bio_info *info = clone->bi_private;
  	struct dm_rq_target_io *tio = info->tio;
  	struct bio *bio = info->orig;
  	unsigned int nr_bytes = info->orig->bi_size;
  
  	bio_put(clone);
  
  	if (tio->error)
  		/*
  		 * An error has already been detected on the request.
  		 * Once error occurred, just let clone->end_io() handle
  		 * the remainder.
  		 */
  		return;
  	else if (error) {
  		/*
  		 * Don't notice the error to the upper layer yet.
  		 * The error handling decision is made by the target driver,
  		 * when the request is completed.
  		 */
  		tio->error = error;
  		return;
  	}
  
  	/*
  	 * I/O for the bio successfully completed.
  	 * Notice the data completion to the upper layer.
  	 */
  
  	/*
  	 * bios are processed from the head of the list.
  	 * So the completing bio should always be rq->bio.
  	 * If it's not, something wrong is happening.
  	 */
  	if (tio->orig->bio != bio)
  		DMERR("bio completion is going in the middle of the request");
  
  	/*
  	 * Update the original request.
  	 * Do not use blk_end_request() here, because it may complete
  	 * the original request before the clone, and break the ordering.
  	 */
  	blk_update_request(tio->orig, 0, nr_bytes);
  }
  
  /*
   * Don't touch any member of the md after calling this function because
   * the md may be freed in dm_put() at the end of this function.
   * Or do dm_get() before calling this function and dm_put() later.
   */
  static void rq_completed(struct mapped_device *md, int run_queue)
  {
  	int wakeup_waiters = 0;
  	struct request_queue *q = md->queue;
  	unsigned long flags;
  
  	spin_lock_irqsave(q->queue_lock, flags);
  	if (!queue_in_flight(q))
  		wakeup_waiters = 1;
  	spin_unlock_irqrestore(q->queue_lock, flags);
  
  	/* nudge anyone waiting on suspend queue */
  	if (wakeup_waiters)
  		wake_up(&md->wait);
  
  	if (run_queue)
  		blk_run_queue(q);
  
  	/*
  	 * dm_put() must be at the end of this function. See the comment above
  	 */
  	dm_put(md);
  }
  
  static void dm_unprep_request(struct request *rq)
  {
  	struct request *clone = rq->special;
  	struct dm_rq_target_io *tio = clone->end_io_data;
  
  	rq->special = NULL;
  	rq->cmd_flags &= ~REQ_DONTPREP;
  
  	blk_rq_unprep_clone(clone);
  	free_rq_tio(tio);
  }
  
  /*
   * Requeue the original request of a clone.
   */
  void dm_requeue_unmapped_request(struct request *clone)
  {
  	struct dm_rq_target_io *tio = clone->end_io_data;
  	struct mapped_device *md = tio->md;
  	struct request *rq = tio->orig;
  	struct request_queue *q = rq->q;
  	unsigned long flags;
  
  	dm_unprep_request(rq);
  
  	spin_lock_irqsave(q->queue_lock, flags);
  	if (elv_queue_empty(q))
  		blk_plug_device(q);
  	blk_requeue_request(q, rq);
  	spin_unlock_irqrestore(q->queue_lock, flags);
  
  	rq_completed(md, 0);
  }
  EXPORT_SYMBOL_GPL(dm_requeue_unmapped_request);
  
  static void __stop_queue(struct request_queue *q)
  {
  	blk_stop_queue(q);
  }
  
  static void stop_queue(struct request_queue *q)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(q->queue_lock, flags);
  	__stop_queue(q);
  	spin_unlock_irqrestore(q->queue_lock, flags);
  }
  
  static void __start_queue(struct request_queue *q)
  {
  	if (blk_queue_stopped(q))
  		blk_start_queue(q);
  }
  
  static void start_queue(struct request_queue *q)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(q->queue_lock, flags);
  	__start_queue(q);
  	spin_unlock_irqrestore(q->queue_lock, flags);
  }
  
  /*
   * Complete the clone and the original request.
   * Must be called without queue lock.
   */
  static void dm_end_request(struct request *clone, int error)
  {
  	struct dm_rq_target_io *tio = clone->end_io_data;
  	struct mapped_device *md = tio->md;
  	struct request *rq = tio->orig;
  
  	if (blk_pc_request(rq)) {
  		rq->errors = clone->errors;
  		rq->resid_len = clone->resid_len;
  
  		if (rq->sense)
  			/*
  			 * We are using the sense buffer of the original
  			 * request.
  			 * So setting the length of the sense data is enough.
  			 */
  			rq->sense_len = clone->sense_len;
  	}
  
  	BUG_ON(clone->bio);
  	free_rq_tio(tio);
  
  	blk_end_request_all(rq, error);
  
  	rq_completed(md, 1);
  }
  
  /*
   * Request completion handler for request-based dm
   */
  static void dm_softirq_done(struct request *rq)
  {
  	struct request *clone = rq->completion_data;
  	struct dm_rq_target_io *tio = clone->end_io_data;
  	dm_request_endio_fn rq_end_io = tio->ti->type->rq_end_io;
  	int error = tio->error;
  
  	if (!(rq->cmd_flags & REQ_FAILED) && rq_end_io)
  		error = rq_end_io(tio->ti, clone, error, &tio->info);
  
  	if (error <= 0)
  		/* The target wants to complete the I/O */
  		dm_end_request(clone, error);
  	else if (error == DM_ENDIO_INCOMPLETE)
  		/* The target will handle the I/O */
  		return;
  	else if (error == DM_ENDIO_REQUEUE)
  		/* The target wants to requeue the I/O */
  		dm_requeue_unmapped_request(clone);
  	else {
  		DMWARN("unimplemented target endio return value: %d", error);
  		BUG();
  	}
  }
  
  /*
   * Complete the clone and the original request with the error status
   * through softirq context.
   */
  static void dm_complete_request(struct request *clone, int error)
  {
  	struct dm_rq_target_io *tio = clone->end_io_data;
  	struct request *rq = tio->orig;
  
  	tio->error = error;
  	rq->completion_data = clone;
  	blk_complete_request(rq);
  }
  
  /*
   * Complete the not-mapped clone and the original request with the error status
   * through softirq context.
   * Target's rq_end_io() function isn't called.
   * This may be used when the target's map_rq() function fails.
   */
  void dm_kill_unmapped_request(struct request *clone, int error)
  {
  	struct dm_rq_target_io *tio = clone->end_io_data;
  	struct request *rq = tio->orig;
  
  	rq->cmd_flags |= REQ_FAILED;
  	dm_complete_request(clone, error);
  }
  EXPORT_SYMBOL_GPL(dm_kill_unmapped_request);
  
  /*
   * Called with the queue lock held
   */
  static void end_clone_request(struct request *clone, int error)
  {
  	/*
  	 * For just cleaning up the information of the queue in which
  	 * the clone was dispatched.
  	 * The clone is *NOT* freed actually here because it is alloced from
  	 * dm own mempool and REQ_ALLOCED isn't set in clone->cmd_flags.
  	 */
  	__blk_put_request(clone->q, clone);
  
  	/*
  	 * Actual request completion is done in a softirq context which doesn't
  	 * hold the queue lock.  Otherwise, deadlock could occur because:
  	 *     - another request may be submitted by the upper level driver
  	 *       of the stacking during the completion
  	 *     - the submission which requires queue lock may be done
  	 *       against this queue
  	 */
  	dm_complete_request(clone, error);
  }

  static sector_t max_io_len(struct mapped_device *md,
  			   sector_t sector, struct dm_target *ti)
  {
  	sector_t offset = sector - ti->begin;
  	sector_t len = ti->len - offset;
  
  	/*
  	 * Does the target need to split even further ?
  	 */
  	if (ti->split_io) {
  		sector_t boundary;
  		boundary = ((offset + ti->split_io) & ~(ti->split_io - 1))
  			   - offset;
  		if (len > boundary)
  			len = boundary;
  	}
  
  	return len;
  }
  
  static void __map_bio(struct dm_target *ti, struct bio *clone,

  		      struct dm_target_io *tio)

  {
  	int r;

  	sector_t sector;

  	struct mapped_device *md;

  	clone->bi_end_io = clone_endio;
  	clone->bi_private = tio;
  
  	/*
  	 * Map the clone.  If r == 0 we don't need to do
  	 * anything, the target has assumed ownership of
  	 * this io.
  	 */
  	atomic_inc(&tio->io->io_count);

  	sector = clone->bi_sector;

  	r = ti->type->map(ti, clone, &tio->info);

  	if (r == DM_MAPIO_REMAPPED) {

  		/* the bio has been remapped so dispatch it */

  		trace_block_remap(bdev_get_queue(clone->bi_bdev), clone,

  				    tio->io->bio->bi_bdev->bd_dev, sector);

  		generic_make_request(clone);

  	} else if (r < 0 || r == DM_MAPIO_REQUEUE) {
  		/* error the io and bail out, or requeue it if needed */

  		md = tio->io->md;
  		dec_pending(tio->io, r);
  		/*
  		 * Store bio_set for cleanup.
  		 */
  		clone->bi_private = md->bs;

  		bio_put(clone);

  		free_tio(md, tio);

  	} else if (r) {
  		DMWARN("unimplemented target map return value: %d", r);
  		BUG();

  	}
  }
  
  struct clone_info {
  	struct mapped_device *md;
  	struct dm_table *map;
  	struct bio *bio;
  	struct dm_io *io;
  	sector_t sector;
  	sector_t sector_count;
  	unsigned short idx;
  };

  static void dm_bio_destructor(struct bio *bio)
  {

  	struct bio_set *bs = bio->bi_private;
  
  	bio_free(bio, bs);

  }

  /*
   * Creates a little bio that is just does part of a bvec.
   */
  static struct bio *split_bvec(struct bio *bio, sector_t sector,
  			      unsigned short idx, unsigned int offset,

  			      unsigned int len, struct bio_set *bs)

  {
  	struct bio *clone;
  	struct bio_vec *bv = bio->bi_io_vec + idx;

  	clone = bio_alloc_bioset(GFP_NOIO, 1, bs);

  	clone->bi_destructor = dm_bio_destructor;

  	*clone->bi_io_vec = *bv;
  
  	clone->bi_sector = sector;
  	clone->bi_bdev = bio->bi_bdev;

  	clone->bi_rw = bio->bi_rw & ~(1 << BIO_RW_BARRIER);

  	clone->bi_vcnt = 1;
  	clone->bi_size = to_bytes(len);
  	clone->bi_io_vec->bv_offset = offset;
  	clone->bi_io_vec->bv_len = clone->bi_size;

  	clone->bi_flags |= 1 << BIO_CLONED;

  	if (bio_integrity(bio)) {

  		bio_integrity_clone(clone, bio, GFP_NOIO, bs);

  		bio_integrity_trim(clone,
  				   bio_sector_offset(bio, idx, offset), len);
  	}

  	return clone;
  }
  
  /*
   * Creates a bio that consists of range of complete bvecs.
   */
  static struct bio *clone_bio(struct bio *bio, sector_t sector,
  			     unsigned short idx, unsigned short bv_count,

  			     unsigned int len, struct bio_set *bs)

  {
  	struct bio *clone;

  	clone = bio_alloc_bioset(GFP_NOIO, bio->bi_max_vecs, bs);
  	__bio_clone(clone, bio);

  	clone->bi_rw &= ~(1 << BIO_RW_BARRIER);

  	clone->bi_destructor = dm_bio_destructor;

  	clone->bi_sector = sector;
  	clone->bi_idx = idx;
  	clone->bi_vcnt = idx + bv_count;
  	clone->bi_size = to_bytes(len);
  	clone->bi_flags &= ~(1 << BIO_SEG_VALID);

  	if (bio_integrity(bio)) {

  		bio_integrity_clone(clone, bio, GFP_NOIO, bs);

  
  		if (idx != bio->bi_idx || clone->bi_size < bio->bi_size)
  			bio_integrity_trim(clone,
  					   bio_sector_offset(bio, idx, 0), len);
  	}

  	return clone;
  }

  static struct dm_target_io *alloc_tio(struct clone_info *ci,
  				      struct dm_target *ti)

  {

  	struct dm_target_io *tio = mempool_alloc(ci->md->tio_pool, GFP_NOIO);

  
  	tio->io = ci->io;
  	tio->ti = ti;

  	memset(&tio->info, 0, sizeof(tio->info));

  
  	return tio;
  }
  
  static void __flush_target(struct clone_info *ci, struct dm_target *ti,
  			  unsigned flush_nr)
  {
  	struct dm_target_io *tio = alloc_tio(ci, ti);
  	struct bio *clone;

  	tio->info.flush_request = flush_nr;
  
  	clone = bio_alloc_bioset(GFP_NOIO, 0, ci->md->bs);
  	__bio_clone(clone, ci->bio);
  	clone->bi_destructor = dm_bio_destructor;
  
  	__map_bio(ti, clone, tio);
  }
  
  static int __clone_and_map_empty_barrier(struct clone_info *ci)
  {
  	unsigned target_nr = 0, flush_nr;
  	struct dm_target *ti;
  
  	while ((ti = dm_table_get_target(ci->map, target_nr++)))
  		for (flush_nr = 0; flush_nr < ti->num_flush_requests;
  		     flush_nr++)
  			__flush_target(ci, ti, flush_nr);
  
  	ci->sector_count = 0;
  
  	return 0;
  }

  static int __clone_and_map(struct clone_info *ci)

  {
  	struct bio *clone, *bio = ci->bio;

  	struct dm_target *ti;
  	sector_t len = 0, max;

  	struct dm_target_io *tio;

  	if (unlikely(bio_empty_barrier(bio)))
  		return __clone_and_map_empty_barrier(ci);

  	ti = dm_table_find_target(ci->map, ci->sector);
  	if (!dm_target_is_valid(ti))
  		return -EIO;
  
  	max = max_io_len(ci->md, ci->sector, ti);

  	/*
  	 * Allocate a target io object.
  	 */

  	tio = alloc_tio(ci, ti);

  
  	if (ci->sector_count <= max) {
  		/*
  		 * Optimise for the simple case where we can do all of
  		 * the remaining io with a single clone.
  		 */
  		clone = clone_bio(bio, ci->sector, ci->idx,

  				  bio->bi_vcnt - ci->idx, ci->sector_count,
  				  ci->md->bs);

  		__map_bio(ti, clone, tio);
  		ci->sector_count = 0;
  
  	} else if (to_sector(bio->bi_io_vec[ci->idx].bv_len) <= max) {
  		/*
  		 * There are some bvecs that don't span targets.
  		 * Do as many of these as possible.
  		 */
  		int i;
  		sector_t remaining = max;
  		sector_t bv_len;
  
  		for (i = ci->idx; remaining && (i < bio->bi_vcnt); i++) {
  			bv_len = to_sector(bio->bi_io_vec[i].bv_len);
  
  			if (bv_len > remaining)
  				break;
  
  			remaining -= bv_len;
  			len += bv_len;
  		}

  		clone = clone_bio(bio, ci->sector, ci->idx, i - ci->idx, len,
  				  ci->md->bs);

  		__map_bio(ti, clone, tio);
  
  		ci->sector += len;
  		ci->sector_count -= len;
  		ci->idx = i;
  
  	} else {
  		/*

  		 * Handle a bvec that must be split between two or more targets.

  		 */
  		struct bio_vec *bv = bio->bi_io_vec + ci->idx;

  		sector_t remaining = to_sector(bv->bv_len);
  		unsigned int offset = 0;

  		do {
  			if (offset) {
  				ti = dm_table_find_target(ci->map, ci->sector);

  				if (!dm_target_is_valid(ti))
  					return -EIO;

  				max = max_io_len(ci->md, ci->sector, ti);

  				tio = alloc_tio(ci, ti);

  			}
  
  			len = min(remaining, max);
  
  			clone = split_bvec(bio, ci->sector, ci->idx,

  					   bv->bv_offset + offset, len,
  					   ci->md->bs);

  
  			__map_bio(ti, clone, tio);
  
  			ci->sector += len;
  			ci->sector_count -= len;
  			offset += to_bytes(len);
  		} while (remaining -= len);

  		ci->idx++;
  	}

  
  	return 0;

  }
  
  /*

   * Split the bio into several clones and submit it to targets.

   */

  static void __split_and_process_bio(struct mapped_device *md, struct bio *bio)

  {
  	struct clone_info ci;

  	int error = 0;

  
  	ci.map = dm_get_table(md);

  	if (unlikely(!ci.map)) {

  		if (!bio_barrier(bio))
  			bio_io_error(bio);
  		else

  			if (!md->barrier_error)
  				md->barrier_error = -EIO;

  		return;
  	}

  	ci.md = md;
  	ci.bio = bio;
  	ci.io = alloc_io(md);
  	ci.io->error = 0;
  	atomic_set(&ci.io->io_count, 1);
  	ci.io->bio = bio;
  	ci.io->md = md;
  	ci.sector = bio->bi_sector;
  	ci.sector_count = bio_sectors(bio);

  	if (unlikely(bio_empty_barrier(bio)))
  		ci.sector_count = 1;

  	ci.idx = bio->bi_idx;

  	start_io_acct(ci.io);

  	while (ci.sector_count && !error)
  		error = __clone_and_map(&ci);

  
  	/* drop the extra reference count */

  	dec_pending(ci.io, error);

  	dm_table_put(ci.map);
  }
  /*-----------------------------------------------------------------
   * CRUD END
   *---------------------------------------------------------------*/

  static int dm_merge_bvec(struct request_queue *q,
  			 struct bvec_merge_data *bvm,
  			 struct bio_vec *biovec)
  {
  	struct mapped_device *md = q->queuedata;
  	struct dm_table *map = dm_get_table(md);
  	struct dm_target *ti;
  	sector_t max_sectors;

  	int max_size = 0;

  
  	if (unlikely(!map))

  		goto out;

  
  	ti = dm_table_find_target(map, bvm->bi_sector);

  	if (!dm_target_is_valid(ti))
  		goto out_table;

  
  	/*
  	 * Find maximum amount of I/O that won't need splitting
  	 */
  	max_sectors = min(max_io_len(md, bvm->bi_sector, ti),
  			  (sector_t) BIO_MAX_SECTORS);
  	max_size = (max_sectors << SECTOR_SHIFT) - bvm->bi_size;
  	if (max_size < 0)
  		max_size = 0;
  
  	/*
  	 * merge_bvec_fn() returns number of bytes
  	 * it can accept at this offset
  	 * max is precomputed maximal io size
  	 */
  	if (max_size && ti->type->merge)
  		max_size = ti->type->merge(ti, bvm, biovec, max_size);

  	/*
  	 * If the target doesn't support merge method and some of the devices
  	 * provided their merge_bvec method (we know this by looking at
  	 * queue_max_hw_sectors), then we can't allow bios with multiple vector
  	 * entries.  So always set max_size to 0, and the code below allows
  	 * just one page.
  	 */
  	else if (queue_max_hw_sectors(q) <= PAGE_SIZE >> 9)
  
  		max_size = 0;

  out_table:

  	dm_table_put(map);
  
  out:

  	/*
  	 * Always allow an entire first page
  	 */
  	if (max_size <= biovec->bv_len && !(bvm->bi_size >> SECTOR_SHIFT))
  		max_size = biovec->bv_len;

  	return max_size;
  }

  /*
   * The request function that just remaps the bio built up by
   * dm_merge_bvec.
   */

  static int _dm_request(struct request_queue *q, struct bio *bio)

  {

  	int rw = bio_data_dir(bio);

  	struct mapped_device *md = q->queuedata;

  	int cpu;

  	down_read(&md->io_lock);

  	cpu = part_stat_lock();
  	part_stat_inc(cpu, &dm_disk(md)->part0, ios[rw]);
  	part_stat_add(cpu, &dm_disk(md)->part0, sectors[rw], bio_sectors(bio));
  	part_stat_unlock();

  	/*

  	 * If we're suspended or the thread is processing barriers
  	 * we have to queue this io for later.

  	 */

  	if (unlikely(test_bit(DMF_QUEUE_IO_TO_THREAD, &md->flags)) ||
  	    unlikely(bio_barrier(bio))) {

  		up_read(&md->io_lock);

  		if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)) &&
  		    bio_rw(bio) == READA) {
  			bio_io_error(bio);
  			return 0;
  		}

  		queue_io(md, bio);

  		return 0;

  	}

  	__split_and_process_bio(md, bio);

  	up_read(&md->io_lock);

  	return 0;

  }

  static int dm_make_request(struct request_queue *q, struct bio *bio)
  {
  	struct mapped_device *md = q->queuedata;
  
  	if (unlikely(bio_barrier(bio))) {
  		bio_endio(bio, -EOPNOTSUPP);
  		return 0;
  	}
  
  	return md->saved_make_request_fn(q, bio); /* call __make_request() */
  }
  
  static int dm_request_based(struct mapped_device *md)
  {
  	return blk_queue_stackable(md->queue);
  }
  
  static int dm_request(struct request_queue *q, struct bio *bio)
  {
  	struct mapped_device *md = q->queuedata;
  
  	if (dm_request_based(md))
  		return dm_make_request(q, bio);
  
  	return _dm_request(q, bio);
  }
  
  void dm_dispatch_request(struct request *rq)
  {
  	int r;
  
  	if (blk_queue_io_stat(rq->q))
  		rq->cmd_flags |= REQ_IO_STAT;
  
  	rq->start_time = jiffies;
  	r = blk_insert_cloned_request(rq->q, rq);
  	if (r)
  		dm_complete_request(rq, r);
  }
  EXPORT_SYMBOL_GPL(dm_dispatch_request);
  
  static void dm_rq_bio_destructor(struct bio *bio)
  {
  	struct dm_rq_clone_bio_info *info = bio->bi_private;
  	struct mapped_device *md = info->tio->md;
  
  	free_bio_info(info);
  	bio_free(bio, md->bs);
  }
  
  static int dm_rq_bio_constructor(struct bio *bio, struct bio *bio_orig,
  				 void *data)
  {
  	struct dm_rq_target_io *tio = data;
  	struct mapped_device *md = tio->md;
  	struct dm_rq_clone_bio_info *info = alloc_bio_info(md);
  
  	if (!info)
  		return -ENOMEM;
  
  	info->orig = bio_orig;
  	info->tio = tio;
  	bio->bi_end_io = end_clone_bio;
  	bio->bi_private = info;
  	bio->bi_destructor = dm_rq_bio_destructor;
  
  	return 0;
  }
  
  static int setup_clone(struct request *clone, struct request *rq,
  		       struct dm_rq_target_io *tio)
  {
  	int r = blk_rq_prep_clone(clone, rq, tio->md->bs, GFP_ATOMIC,
  				  dm_rq_bio_constructor, tio);
  
  	if (r)
  		return r;
  
  	clone->cmd = rq->cmd;
  	clone->cmd_len = rq->cmd_len;
  	clone->sense = rq->sense;
  	clone->buffer = rq->buffer;
  	clone->end_io = end_clone_request;
  	clone->end_io_data = tio;
  
  	return 0;
  }
  
  static int dm_rq_flush_suspending(struct mapped_device *md)
  {
  	return !md->suspend_rq.special;
  }
  
  /*
   * Called with the queue lock held.
   */
  static int dm_prep_fn(struct request_queue *q, struct request *rq)
  {
  	struct mapped_device *md = q->queuedata;
  	struct dm_rq_target_io *tio;
  	struct request *clone;
  
  	if (unlikely(rq == &md->suspend_rq)) {
  		if (dm_rq_flush_suspending(md))
  			return BLKPREP_OK;
  		else
  			/* The flush suspend was interrupted */
  			return BLKPREP_KILL;
  	}
  
  	if (unlikely(rq->special)) {
  		DMWARN("Already has something in rq->special.");
  		return BLKPREP_KILL;
  	}
  
  	tio = alloc_rq_tio(md); /* Only one for each original request */
  	if (!tio)
  		/* -ENOMEM */
  		return BLKPREP_DEFER;
  
  	tio->md = md;
  	tio->ti = NULL;
  	tio->orig = rq;
  	tio->error = 0;
  	memset(&tio->info, 0, sizeof(tio->info));
  
  	clone = &tio->clone;
  	if (setup_clone(clone, rq, tio)) {
  		/* -ENOMEM */
  		free_rq_tio(tio);
  		return BLKPREP_DEFER;
  	}
  
  	rq->special = clone;
  	rq->cmd_flags |= REQ_DONTPREP;
  
  	return BLKPREP_OK;
  }
  
  static void map_request(struct dm_target *ti, struct request *rq,
  			struct mapped_device *md)
  {
  	int r;
  	struct request *clone = rq->special;
  	struct dm_rq_target_io *tio = clone->end_io_data;
  
  	/*
  	 * Hold the md reference here for the in-flight I/O.
  	 * We can't rely on the reference count by device opener,
  	 * because the device may be closed during the request completion
  	 * when all bios are completed.
  	 * See the comment in rq_completed() too.
  	 */
  	dm_get(md);
  
  	tio->ti = ti;
  	r = ti->type->map_rq(ti, clone, &tio->info);
  	switch (r) {
  	case DM_MAPIO_SUBMITTED:
  		/* The target has taken the I/O to submit by itself later */
  		break;
  	case DM_MAPIO_REMAPPED:
  		/* The target has remapped the I/O so dispatch it */
  		dm_dispatch_request(clone);
  		break;
  	case DM_MAPIO_REQUEUE:
  		/* The target wants to requeue the I/O */
  		dm_requeue_unmapped_request(clone);
  		break;
  	default:
  		if (r > 0) {
  			DMWARN("unimplemented target map return value: %d", r);
  			BUG();
  		}
  
  		/* The target wants to complete the I/O */
  		dm_kill_unmapped_request(clone, r);
  		break;
  	}
  }
  
  /*
   * q->request_fn for request-based dm.
   * Called with the queue lock held.
   */
  static void dm_request_fn(struct request_queue *q)
  {
  	struct mapped_device *md = q->queuedata;
  	struct dm_table *map = dm_get_table(md);
  	struct dm_target *ti;
  	struct request *rq;
  
  	/*
  	 * For noflush suspend, check blk_queue_stopped() to immediately
  	 * quit I/O dispatching.
  	 */
  	while (!blk_queue_plugged(q) && !blk_queue_stopped(q)) {
  		rq = blk_peek_request(q);
  		if (!rq)
  			goto plug_and_out;
  
  		if (unlikely(rq == &md->suspend_rq)) { /* Flush suspend maker */
  			if (queue_in_flight(q))
  				/* Not quiet yet.  Wait more */
  				goto plug_and_out;
  
  			/* This device should be quiet now */
  			__stop_queue(q);
  			blk_start_request(rq);
  			__blk_end_request_all(rq, 0);
  			wake_up(&md->wait);
  			goto out;
  		}
  
  		ti = dm_table_find_target(map, blk_rq_pos(rq));
  		if (ti->type->busy && ti->type->busy(ti))
  			goto plug_and_out;
  
  		blk_start_request(rq);
  		spin_unlock(q->queue_lock);
  		map_request(ti, rq, md);
  		spin_lock_irq(q->queue_lock);
  	}
  
  	goto out;
  
  plug_and_out:
  	if (!elv_queue_empty(q))
  		/* Some requests still remain, retry later */
  		blk_plug_device(q);
  
  out:
  	dm_table_put(map);
  
  	return;
  }
  
  int dm_underlying_device_busy(struct request_queue *q)
  {
  	return blk_lld_busy(q);
  }
  EXPORT_SYMBOL_GPL(dm_underlying_device_busy);
  
  static int dm_lld_busy(struct request_queue *q)
  {
  	int r;
  	struct mapped_device *md = q->queuedata;
  	struct dm_table *map = dm_get_table(md);
  
  	if (!map || test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags))
  		r = 1;
  	else
  		r = dm_table_any_busy_target(map);
  
  	dm_table_put(map);
  
  	return r;
  }

  static void dm_unplug_all(struct request_queue *q)

  {
  	struct mapped_device *md = q->queuedata;
  	struct dm_table *map = dm_get_table(md);
  
  	if (map) {

  		if (dm_request_based(md))
  			generic_unplug_device(q);

  		dm_table_unplug_all(map);
  		dm_table_put(map);
  	}
  }
  
  static int dm_any_congested(void *congested_data, int bdi_bits)
  {

  	int r = bdi_bits;
  	struct mapped_device *md = congested_data;
  	struct dm_table *map;

  	if (!test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)) {

  		map = dm_get_table(md);
  		if (map) {

  			/*
  			 * Request-based dm cares about only own queue for
  			 * the query about congestion status of request_queue
  			 */
  			if (dm_request_based(md))
  				r = md->queue->backing_dev_info.state &
  				    bdi_bits;
  			else
  				r = dm_table_any_congested(map, bdi_bits);

  			dm_table_put(map);
  		}
  	}

  	return r;
  }
  
  /*-----------------------------------------------------------------
   * An IDR is used to keep track of allocated minor numbers.
   *---------------------------------------------------------------*/

  static DEFINE_IDR(_minor_idr);

  static void free_minor(int minor)

  {

  	spin_lock(&_minor_lock);

  	idr_remove(&_minor_idr, minor);

  	spin_unlock(&_minor_lock);

  }
  
  /*
   * See if the device with a specific minor # is free.
   */

  static int specific_minor(int minor)

  {
  	int r, m;
  
  	if (minor >= (1 << MINORBITS))
  		return -EINVAL;

  	r = idr_pre_get(&_minor_idr, GFP_KERNEL);
  	if (!r)
  		return -ENOMEM;

  	spin_lock(&_minor_lock);

  
  	if (idr_find(&_minor_idr, minor)) {
  		r = -EBUSY;
  		goto out;
  	}

  	r = idr_get_new_above(&_minor_idr, MINOR_ALLOCED, minor, &m);

  	if (r)

  		goto out;

  
  	if (m != minor) {
  		idr_remove(&_minor_idr, m);
  		r = -EBUSY;
  		goto out;
  	}
  
  out:

  	spin_unlock(&_minor_lock);

  	return r;
  }

  static int next_free_minor(int *minor)

  {

  	int r, m;

  	r = idr_pre_get(&_minor_idr, GFP_KERNEL);

  	if (!r)
  		return -ENOMEM;

  	spin_lock(&_minor_lock);

  	r = idr_get_new(&_minor_idr, MINOR_ALLOCED, &m);

  	if (r)

  		goto out;

  
  	if (m >= (1 << MINORBITS)) {
  		idr_remove(&_minor_idr, m);
  		r = -ENOSPC;
  		goto out;
  	}
  
  	*minor = m;
  
  out:

  	spin_unlock(&_minor_lock);

  	return r;
  }
  
  static struct block_device_operations dm_blk_dops;

  static void dm_wq_work(struct work_struct *work);

  /*
   * Allocate and initialise a blank device with a given minor.
   */

  static struct mapped_device *alloc_dev(int minor)

  {
  	int r;

  	struct mapped_device *md = kzalloc(sizeof(*md), GFP_KERNEL);

  	void *old_md;

  
  	if (!md) {
  		DMWARN("unable to allocate device, out of memory.");
  		return NULL;
  	}

  	if (!try_module_get(THIS_MODULE))

  		goto bad_module_get;

  	/* get a minor number for the dev */

  	if (minor == DM_ANY_MINOR)

  		r = next_free_minor(&minor);

  	else

  		r = specific_minor(minor);

  	if (r < 0)

  		goto bad_minor;

  	init_rwsem(&md->io_lock);

  	mutex_init(&md->suspend_lock);

  	spin_lock_init(&md->deferred_lock);

  	rwlock_init(&md->map_lock);
  	atomic_set(&md->holders, 1);

  	atomic_set(&md->open_count, 0);

  	atomic_set(&md->event_nr, 0);

  	atomic_set(&md->uevent_seq, 0);
  	INIT_LIST_HEAD(&md->uevent_list);
  	spin_lock_init(&md->uevent_lock);

  	md->queue = blk_init_queue(dm_request_fn, NULL);

  	if (!md->queue)

  		goto bad_queue;

  	/*
  	 * Request-based dm devices cannot be stacked on top of bio-based dm
  	 * devices.  The type of this dm device has not been decided yet,
  	 * although we initialized the queue using blk_init_queue().
  	 * The type is decided at the first table loading time.
  	 * To prevent problematic device stacking, clear the queue flag
  	 * for request stacking support until then.
  	 *
  	 * This queue is new, so no concurrency on the queue_flags.
  	 */
  	queue_flag_clear_unlocked(QUEUE_FLAG_STACKABLE, md->queue);
  	md->saved_make_request_fn = md->queue->make_request_fn;

  	md->queue->queuedata = md;
  	md->queue->backing_dev_info.congested_fn = dm_any_congested;
  	md->queue->backing_dev_info.congested_data = md;
  	blk_queue_make_request(md->queue, dm_request);

  	blk_queue_bounce_limit(md->queue, BLK_BOUNCE_ANY);

  	md->queue->unplug_fn = dm_unplug_all;

  	blk_queue_merge_bvec(md->queue, dm_merge_bvec);

  	blk_queue_softirq_done(md->queue, dm_softirq_done);
  	blk_queue_prep_rq(md->queue, dm_prep_fn);
  	blk_queue_lld_busy(md->queue, dm_lld_busy);

  	md->disk = alloc_disk(1);
  	if (!md->disk)

  		goto bad_disk;

  	atomic_set(&md->pending, 0);
  	init_waitqueue_head(&md->wait);

  	INIT_WORK(&md->work, dm_wq_work);

  	init_waitqueue_head(&md->eventq);

  	md->disk->major = _major;
  	md->disk->first_minor = minor;
  	md->disk->fops = &dm_blk_dops;
  	md->disk->queue = md->queue;
  	md->disk->private_data = md;
  	sprintf(md->disk->disk_name, "dm-%d", minor);
  	add_disk(md->disk);

  	format_dev_t(md->name, MKDEV(_major, minor));

  	md->wq = create_singlethread_workqueue("kdmflush");
  	if (!md->wq)
  		goto bad_thread;

  	md->bdev = bdget_disk(md->disk, 0);
  	if (!md->bdev)
  		goto bad_bdev;

  	/* Populate the mapping, nobody knows we exist yet */

  	spin_lock(&_minor_lock);

  	old_md = idr_replace(&_minor_idr, md, minor);

  	spin_unlock(&_minor_lock);

  
  	BUG_ON(old_md != MINOR_ALLOCED);

  	return md;

  bad_bdev:
  	destroy_workqueue(md->wq);

  bad_thread:
  	put_disk(md->disk);

  bad_disk:

  	blk_cleanup_queue(md->queue);

  bad_queue:

  	free_minor(minor);

  bad_minor:

  	module_put(THIS_MODULE);

  bad_module_get:

  	kfree(md);
  	return NULL;
  }

  static void unlock_fs(struct mapped_device *md);

  static void free_dev(struct mapped_device *md)
  {

  	int minor = MINOR(disk_devt(md->disk));

  	unlock_fs(md);
  	bdput(md->bdev);

  	destroy_workqueue(md->wq);

  	if (md->tio_pool)
  		mempool_destroy(md->tio_pool);
  	if (md->io_pool)
  		mempool_destroy(md->io_pool);
  	if (md->bs)
  		bioset_free(md->bs);

  	blk_integrity_unregister(md->disk);

  	del_gendisk(md->disk);

  	free_minor(minor);

  
  	spin_lock(&_minor_lock);
  	md->disk->private_data = NULL;
  	spin_unlock(&_minor_lock);

  	put_disk(md->disk);

  	blk_cleanup_queue(md->queue);

  	module_put(THIS_MODULE);

  	kfree(md);
  }

  static void __bind_mempools(struct mapped_device *md, struct dm_table *t)
  {
  	struct dm_md_mempools *p;
  
  	if (md->io_pool && md->tio_pool && md->bs)
  		/* the md already has necessary mempools */
  		goto out;
  
  	p = dm_table_get_md_mempools(t);
  	BUG_ON(!p || md->io_pool || md->tio_pool || md->bs);
  
  	md->io_pool = p->io_pool;
  	p->io_pool = NULL;
  	md->tio_pool = p->tio_pool;
  	p->tio_pool = NULL;
  	md->bs = p->bs;
  	p->bs = NULL;
  
  out:
  	/* mempool bind completed, now no need any mempools in the table */
  	dm_table_free_md_mempools(t);
  }

  /*
   * Bind a table to the device.
   */
  static void event_callback(void *context)
  {

  	unsigned long flags;
  	LIST_HEAD(uevents);

  	struct mapped_device *md = (struct mapped_device *) context;

  	spin_lock_irqsave(&md->uevent_lock, flags);
  	list_splice_init(&md->uevent_list, &uevents);
  	spin_unlock_irqrestore(&md->uevent_lock, flags);

  	dm_send_uevents(&uevents, &disk_to_dev(md->disk)->kobj);

  	atomic_inc(&md->event_nr);
  	wake_up(&md->eventq);
  }

  static void __set_size(struct mapped_device *md, sector_t size)

  {

  	set_capacity(md->disk, size);

  	mutex_lock(&md->bdev->bd_inode->i_mutex);
  	i_size_write(md->bdev->bd_inode, (loff_t)size << SECTOR_SHIFT);
  	mutex_unlock(&md->bdev->bd_inode->i_mutex);

  }

  static int __bind(struct mapped_device *md, struct dm_table *t,
  		  struct queue_limits *limits)

  {

  	struct request_queue *q = md->queue;

  	sector_t size;

  	unsigned long flags;

  
  	size = dm_table_get_size(t);

  
  	/*
  	 * Wipe any geometry if the size of the table changed.
  	 */
  	if (size != get_capacity(md->disk))
  		memset(&md->geometry, 0, sizeof(md->geometry));

  	__set_size(md, size);

  
  	if (!size) {
  		dm_table_destroy(t);

  		return 0;

  	}

  	dm_table_event_callback(t, event_callback, md);

  	/*
  	 * The queue hasn't been stopped yet, if the old table type wasn't
  	 * for request-based during suspension.  So stop it to prevent
  	 * I/O mapping before resume.
  	 * This must be done before setting the queue restrictions,
  	 * because request-based dm may be run just after the setting.
  	 */
  	if (dm_table_request_based(t) && !blk_queue_stopped(q))
  		stop_queue(q);
  
  	__bind_mempools(md, t);

  	write_lock_irqsave(&md->map_lock, flags);

  	md->map = t;

  	dm_table_set_restrictions(t, q, limits);

  	write_unlock_irqrestore(&md->map_lock, flags);

  	return 0;
  }
  
  static void __unbind(struct mapped_device *md)
  {
  	struct dm_table *map = md->map;

  	unsigned long flags;

  
  	if (!map)
  		return;
  
  	dm_table_event_callback(map, NULL, NULL);

  	write_lock_irqsave(&md->map_lock, flags);

  	md->map = NULL;

  	write_unlock_irqrestore(&md->map_lock, flags);

  	dm_table_destroy(map);

  }
  
  /*
   * Constructor for a new device.
   */

  int dm_create(int minor, struct mapped_device **result)

  {
  	struct mapped_device *md;

  	md = alloc_dev(minor);

  	if (!md)
  		return -ENXIO;

  	dm_sysfs_init(md);

  	*result = md;
  	return 0;
  }

  static struct mapped_device *dm_find_md(dev_t dev)

  {
  	struct mapped_device *md;

  	unsigned minor = MINOR(dev);
  
  	if (MAJOR(dev) != _major || minor >= (1 << MINORBITS))
  		return NULL;

  	spin_lock(&_minor_lock);

  
  	md = idr_find(&_minor_idr, minor);

  	if (md && (md == MINOR_ALLOCED ||

  		   (MINOR(disk_devt(dm_disk(md))) != minor) ||

  		   test_bit(DMF_FREEING, &md->flags))) {

  		md = NULL;

  		goto out;
  	}

  out:

  	spin_unlock(&_minor_lock);

  	return md;
  }

  struct mapped_device *dm_get_md(dev_t dev)
  {
  	struct mapped_device *md = dm_find_md(dev);
  
  	if (md)
  		dm_get(md);
  
  	return md;
  }

  void *dm_get_mdptr(struct mapped_device *md)

  {

  	return md->interface_ptr;

  }
  
  void dm_set_mdptr(struct mapped_device *md, void *ptr)
  {
  	md->interface_ptr = ptr;
  }
  
  void dm_get(struct mapped_device *md)
  {
  	atomic_inc(&md->holders);
  }

  const char *dm_device_name(struct mapped_device *md)
  {
  	return md->name;
  }
  EXPORT_SYMBOL_GPL(dm_device_name);

  void dm_put(struct mapped_device *md)
  {

  	struct dm_table *map;

  	BUG_ON(test_bit(DMF_FREEING, &md->flags));

  	if (atomic_dec_and_lock(&md->holders, &_minor_lock)) {

  		map = dm_get_table(md);

  		idr_replace(&_minor_idr, MINOR_ALLOCED,
  			    MINOR(disk_devt(dm_disk(md))));

  		set_bit(DMF_FREEING, &md->flags);

  		spin_unlock(&_minor_lock);

  		if (!dm_suspended(md)) {

  			dm_table_presuspend_targets(map);
  			dm_table_postsuspend_targets(map);
  		}

  		dm_sysfs_exit(md);

  		dm_table_put(map);

  		__unbind(md);

  		free_dev(md);
  	}

  }

  EXPORT_SYMBOL_GPL(dm_put);

  static int dm_wait_for_completion(struct mapped_device *md, int interruptible)

  {
  	int r = 0;

  	DECLARE_WAITQUEUE(wait, current);

  	struct request_queue *q = md->queue;
  	unsigned long flags;

  
  	dm_unplug_all(md->queue);
  
  	add_wait_queue(&md->wait, &wait);

  
  	while (1) {

  		set_current_state(interruptible);

  
  		smp_mb();

  		if (dm_request_based(md)) {
  			spin_lock_irqsave(q->queue_lock, flags);
  			if (!queue_in_flight(q) && blk_queue_stopped(q)) {
  				spin_unlock_irqrestore(q->queue_lock, flags);
  				break;
  			}
  			spin_unlock_irqrestore(q->queue_lock, flags);
  		} else if (!atomic_read(&md->pending))

  			break;

  		if (interruptible == TASK_INTERRUPTIBLE &&
  		    signal_pending(current)) {

  			r = -EINTR;
  			break;
  		}
  
  		io_schedule();
  	}
  	set_current_state(TASK_RUNNING);

  	remove_wait_queue(&md->wait, &wait);

  	return r;
  }

  static void dm_flush(struct mapped_device *md)

  {
  	dm_wait_for_completion(md, TASK_UNINTERRUPTIBLE);

  
  	bio_init(&md->barrier_bio);
  	md->barrier_bio.bi_bdev = md->bdev;
  	md->barrier_bio.bi_rw = WRITE_BARRIER;
  	__split_and_process_bio(md, &md->barrier_bio);
  
  	dm_wait_for_completion(md, TASK_UNINTERRUPTIBLE);

  }
  
  static void process_barrier(struct mapped_device *md, struct bio *bio)
  {

  	md->barrier_error = 0;

  	dm_flush(md);

  	if (!bio_empty_barrier(bio)) {
  		__split_and_process_bio(md, bio);
  		dm_flush(md);

  	}

  	if (md->barrier_error != DM_ENDIO_REQUEUE)

  		bio_endio(bio, md->barrier_error);

  	else {
  		spin_lock_irq(&md->deferred_lock);
  		bio_list_add_head(&md->deferred, bio);
  		spin_unlock_irq(&md->deferred_lock);
  	}

  }

  /*
   * Process the deferred bios
   */

  static void dm_wq_work(struct work_struct *work)

  {

  	struct mapped_device *md = container_of(work, struct mapped_device,
  						work);

  	struct bio *c;

  	down_write(&md->io_lock);

  	while (!test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)) {

  		spin_lock_irq(&md->deferred_lock);
  		c = bio_list_pop(&md->deferred);
  		spin_unlock_irq(&md->deferred_lock);
  
  		if (!c) {

  			clear_bit(DMF_QUEUE_IO_TO_THREAD, &md->flags);

  			break;
  		}

  		up_write(&md->io_lock);

  		if (dm_request_based(md))
  			generic_make_request(c);
  		else {
  			if (bio_barrier(c))
  				process_barrier(md, c);
  			else
  				__split_and_process_bio(md, c);
  		}

  
  		down_write(&md->io_lock);

  	}

  	up_write(&md->io_lock);

  }

  static void dm_queue_flush(struct mapped_device *md)

  {

  	clear_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags);
  	smp_mb__after_clear_bit();

  	queue_work(md->wq, &md->work);

  }

  /*
   * Swap in a new table (destroying old one).
   */
  int dm_swap_table(struct mapped_device *md, struct dm_table *table)
  {

  	struct queue_limits limits;

  	int r = -EINVAL;

  	mutex_lock(&md->suspend_lock);

  
  	/* device must be suspended */

  	if (!dm_suspended(md))

  		goto out;

  	r = dm_calculate_queue_limits(table, &limits);
  	if (r)
  		goto out;

  	/* cannot change the device type, once a table is bound */
  	if (md->map &&
  	    (dm_table_get_type(md->map) != dm_table_get_type(table))) {
  		DMWARN("can't change the device type after a table is bound");
  		goto out;
  	}

  	/*
  	 * It is enought that blk_queue_ordered() is called only once when
  	 * the first bio-based table is bound.
  	 *
  	 * This setting should be moved to alloc_dev() when request-based dm
  	 * supports barrier.
  	 */
  	if (!md->map && dm_table_bio_based(table))
  		blk_queue_ordered(md->queue, QUEUE_ORDERED_DRAIN, NULL);

  	__unbind(md);

  	r = __bind(md, table, &limits);

  out:

  	mutex_unlock(&md->suspend_lock);

  	return r;

  }

  static void dm_rq_invalidate_suspend_marker(struct mapped_device *md)
  {
  	md->suspend_rq.special = (void *)0x1;
  }
  
  static void dm_rq_abort_suspend(struct mapped_device *md, int noflush)
  {
  	struct request_queue *q = md->queue;
  	unsigned long flags;
  
  	spin_lock_irqsave(q->queue_lock, flags);
  	if (!noflush)
  		dm_rq_invalidate_suspend_marker(md);
  	__start_queue(q);
  	spin_unlock_irqrestore(q->queue_lock, flags);
  }
  
  static void dm_rq_start_suspend(struct mapped_device *md, int noflush)
  {
  	struct request *rq = &md->suspend_rq;
  	struct request_queue *q = md->queue;
  
  	if (noflush)
  		stop_queue(q);
  	else {
  		blk_rq_init(q, rq);
  		blk_insert_request(q, rq, 0, NULL);
  	}
  }
  
  static int dm_rq_suspend_available(struct mapped_device *md, int noflush)
  {
  	int r = 1;
  	struct request *rq = &md->suspend_rq;
  	struct request_queue *q = md->queue;
  	unsigned long flags;
  
  	if (noflush)
  		return r;
  
  	/* The marker must be protected by queue lock if it is in use */
  	spin_lock_irqsave(q->queue_lock, flags);
  	if (unlikely(rq->ref_count)) {
  		/*
  		 * This can happen, when the previous flush suspend was
  		 * interrupted, the marker is still in the queue and
  		 * this flush suspend has been invoked, because we don't
  		 * remove the marker at the time of suspend interruption.
  		 * We have only one marker per mapped_device, so we can't
  		 * start another flush suspend while it is in use.
  		 */
  		BUG_ON(!rq->special); /* The marker should be invalidated */
  		DMWARN("Invalidating the previous flush suspend is still in"
  		       " progress.  Please retry later.");
  		r = 0;
  	}
  	spin_unlock_irqrestore(q->queue_lock, flags);
  
  	return r;
  }

  /*
   * Functions to lock and unlock any filesystem running on the
   * device.
   */

  static int lock_fs(struct mapped_device *md)

  {

  	int r;

  
  	WARN_ON(md->frozen_sb);

  	md->frozen_sb = freeze_bdev(md->bdev);

  	if (IS_ERR(md->frozen_sb)) {