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dm.c

/*
 * Copyright (C) 2001, 2002 Sistina Software (UK) Limited.
 * Copyright (C) 2004-2006 Red Hat, Inc. All rights reserved.
 *
 * This file is released under the GPL.
 */

#include "dm.h"
#include "dm-bio-list.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 <linux/blktrace_api.h>
#include <linux/smp_lock.h>

#define DM_MSG_PREFIX "core"

static const char *_name = DM_NAME;

static unsigned int major = 0;
static unsigned int _major = 0;

static DEFINE_SPINLOCK(_minor_lock);
/*
 * One of these is allocated per bio.
 */
struct dm_io {
      struct mapped_device *md;
      int error;
      struct bio *bio;
      atomic_t io_count;
      unsigned long start_time;
};

/*
 * 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;
};

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;
}

#define MINOR_ALLOCED ((void *)-1)

/*
 * Bits for the md->flags field.
 */
#define DMF_BLOCK_IO 0
#define DMF_SUSPENDED 1
#define DMF_FROZEN 2
#define DMF_FREEING 3
#define DMF_DELETING 4
#define DMF_NOFLUSH_SUSPENDING 5

struct mapped_device {
      struct rw_semaphore io_lock;
      struct semaphore suspend_lock;
      spinlock_t pushback_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 bio_list deferred;
      struct bio_list pushback;

      /*
       * 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 *suspended_bdev;

      /* forced geometry settings */
      struct hd_geometry geometry;
};

#define MIN_IOS 256
static struct kmem_cache *_io_cache;
static struct kmem_cache *_tio_cache;

static int __init local_init(void)
{
      int r;

      /* allocate a slab for the dm_ios */
      _io_cache = KMEM_CACHE(dm_io, 0);
      if (!_io_cache)
            return -ENOMEM;

      /* allocate a slab for the target ios */
      _tio_cache = KMEM_CACHE(dm_target_io, 0);
      if (!_tio_cache) {
            kmem_cache_destroy(_io_cache);
            return -ENOMEM;
      }

      r = dm_uevent_init();
      if (r) {
            kmem_cache_destroy(_tio_cache);
            kmem_cache_destroy(_io_cache);
            return r;
      }

      _major = major;
      r = register_blkdev(_major, _name);
      if (r < 0) {
            kmem_cache_destroy(_tio_cache);
            kmem_cache_destroy(_io_cache);
            dm_uevent_exit();
            return r;
      }

      if (!_major)
            _major = r;

      return 0;
}

static void local_exit(void)
{
      kmem_cache_destroy(_tio_cache);
      kmem_cache_destroy(_io_cache);
      unregister_blkdev(_major, _name);
      dm_uevent_exit();

      _major = 0;

      DMINFO("cleaned up");
}

int (*_inits[])(void) __initdata = {
      local_init,
      dm_target_init,
      dm_linear_init,
      dm_stripe_init,
      dm_interface_init,
};

void (*_exits[])(void) = {
      local_exit,
      dm_target_exit,
      dm_linear_exit,
      dm_stripe_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 inode *inode, struct file *file)
{
      struct mapped_device *md;

      spin_lock(&_minor_lock);

      md = inode->i_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 inode *inode, struct file *file)
{
      struct mapped_device *md;

      md = inode->i_bdev->bd_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 inode *inode, struct file *file,
                  unsigned int cmd, unsigned long arg)
{
      struct mapped_device *md;
      struct dm_table *map;
      struct dm_target *tgt;
      int r = -ENOTTY;

      /* We don't really need this lock, but we do need 'inode'. */
      unlock_kernel();

      md = inode->i_bdev->bd_disk->private_data;

      map = dm_get_table(md);

      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, inode, file, cmd, arg);

out:
      dm_table_put(map);

      lock_kernel();
      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 struct dm_target_io *alloc_tio(struct mapped_device *md)
{
      return mempool_alloc(md->tio_pool, GFP_NOIO);
}

static void free_tio(struct mapped_device *md, struct dm_target_io *tio)
{
      mempool_free(tio, md->tio_pool);
}

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

      io->start_time = jiffies;

      preempt_disable();
      disk_round_stats(dm_disk(md));
      preempt_enable();
      dm_disk(md)->in_flight = atomic_inc_return(&md->pending);
}

static int 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;
      int rw = bio_data_dir(bio);

      preempt_disable();
      disk_round_stats(dm_disk(md));
      preempt_enable();
      dm_disk(md)->in_flight = pending = atomic_dec_return(&md->pending);

      disk_stat_add(dm_disk(md), ticks[rw], duration);

      return !pending;
}

/*
 * Add the bio to the list of deferred io.
 */
static int queue_io(struct mapped_device *md, struct bio *bio)
{
      down_write(&md->io_lock);

      if (!test_bit(DMF_BLOCK_IO, &md->flags)) {
            up_write(&md->io_lock);
            return 1;
      }

      bio_list_add(&md->deferred, bio);

      up_write(&md->io_lock);
      return 0;         /* deferred successfully */
}

/*
 * 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;

      read_lock(&md->map_lock);
      t = md->map;
      if (t)
            dm_table_get(t);
      read_unlock(&md->map_lock);

      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;

      /* Push-back supersedes any I/O errors */
      if (error && !(io->error > 0 && __noflush_suspending(io->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.
                   * This must be handled before the sleeper on
                   * suspend queue merges the pushback list.
                   */
                  spin_lock_irqsave(&io->md->pushback_lock, flags);
                  if (__noflush_suspending(io->md))
                        bio_list_add(&io->md->pushback, io->bio);
                  else
                        /* noflush suspend was interrupted. */
                        io->error = -EIO;
                  spin_unlock_irqrestore(&io->md->pushback_lock, flags);
            }

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

            if (io->error != DM_ENDIO_REQUEUE) {
                  blk_add_trace_bio(io->md->queue, io->bio,
                                BLK_TA_COMPLETE);

                  bio_endio(io->bio, io->error);
            }

            free_io(io->md, io);
      }
}

static void clone_endio(struct bio *bio, int error)
{
      int r = 0;
      struct dm_target_io *tio = bio->bi_private;
      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();
            }
      }

      dec_pending(tio->io, error);

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

      bio_put(bio);
      free_tio(md, tio);
}

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;

      /*
       * Sanity checks.
       */
      BUG_ON(!clone->bi_size);

      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 */

            blk_add_trace_remap(bdev_get_queue(clone->bi_bdev), clone,
                            tio->io->bio->bi_bdev->bd_dev,
                            clone->bi_sector, 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;
      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;

      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_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);

      return clone;
}

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;

      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->md);
      tio->io = ci->io;
      tio->ti = ti;
      memset(&tio->info, 0, sizeof(tio->info));

      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->md);
                        tio->io = ci->io;
                        tio->ti = ti;
                        memset(&tio->info, 0, sizeof(tio->info));
                  }

                  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.
 */
static int __split_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))
            return -EIO;

      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);
      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);

      return 0;
}
/*-----------------------------------------------------------------
 * CRUD END
 *---------------------------------------------------------------*/

/*
 * 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 r = -EIO;
      int rw = bio_data_dir(bio);
      struct mapped_device *md = q->queuedata;

      /*
       * There is no use in forwarding any barrier request since we can't
       * guarantee it is (or can be) handled by the targets correctly.
       */
      if (unlikely(bio_barrier(bio))) {
            bio_endio(bio, -EOPNOTSUPP);
            return 0;
      }

      down_read(&md->io_lock);

      disk_stat_inc(dm_disk(md), ios[rw]);
      disk_stat_add(dm_disk(md), sectors[rw], bio_sectors(bio));

      /*
       * If we're suspended we have to queue
       * this io for later.
       */
      while (test_bit(DMF_BLOCK_IO, &md->flags)) {
            up_read(&md->io_lock);

            if (bio_rw(bio) != READA)
                  r = queue_io(md, bio);

            if (r <= 0)
                  goto out_req;

            /*
             * We're in a while loop, because someone could suspend
             * before we get to the following read lock.
             */
            down_read(&md->io_lock);
      }

      r = __split_bio(md, bio);
      up_read(&md->io_lock);

out_req:
      if (r < 0)
            bio_io_error(bio);

      return 0;
}

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) {
            dm_table_unplug_all(map);
            dm_table_put(map);
      }
}

static int dm_any_congested(void *congested_data, int bdi_bits)
{
      int r;
      struct mapped_device *md = (struct mapped_device *) congested_data;
      struct dm_table *map = dm_get_table(md);

      if (!map || test_bit(DMF_BLOCK_IO, &md->flags))
            r = 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(struct mapped_device *md, 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(struct mapped_device *md, 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;

/*
 * Allocate and initialise a blank device with a given minor.
 */
static struct mapped_device *alloc_dev(int minor)
{
      int r;
      struct mapped_device *md = kmalloc(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 bad0;

      /* get a minor number for the dev */
      if (minor == DM_ANY_MINOR)
            r = next_free_minor(md, &minor);
      else
            r = specific_minor(md, minor);
      if (r < 0)
            goto bad1;

      memset(md, 0, sizeof(*md));
      init_rwsem(&md->io_lock);
      init_MUTEX(&md->suspend_lock);
      spin_lock_init(&md->pushback_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_alloc_queue(GFP_KERNEL);
      if (!md->queue)
            goto bad1_free_minor;

      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;

      md->io_pool = mempool_create_slab_pool(MIN_IOS, _io_cache);
      if (!md->io_pool)
            goto bad2;

      md->tio_pool = mempool_create_slab_pool(MIN_IOS, _tio_cache);
      if (!md->tio_pool)
            goto bad3;

      md->bs = bioset_create(16, 16);
      if (!md->bs)
            goto bad_no_bioset;

      md->disk = alloc_disk(1);
      if (!md->disk)
            goto bad4;

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

      /* 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;

 bad4:
      bioset_free(md->bs);
 bad_no_bioset:
      mempool_destroy(md->tio_pool);
 bad3:
      mempool_destroy(md->io_pool);
 bad2:
      blk_cleanup_queue(md->queue);
 bad1_free_minor:
      free_minor(minor);
 bad1:
      module_put(THIS_MODULE);
 bad0:
      kfree(md);
      return NULL;
}

static void unlock_fs(struct mapped_device *md);

static void free_dev(struct mapped_device *md)
{
      int minor = md->disk->first_minor;

      if (md->suspended_bdev) {
            unlock_fs(md);
            bdput(md->suspended_bdev);
      }
      mempool_destroy(md->tio_pool);
      mempool_destroy(md->io_pool);
      bioset_free(md->bs);
      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);
}

/*
 * 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, &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->suspended_bdev->bd_inode->i_mutex);
      i_size_write(md->suspended_bdev->bd_inode, (loff_t)size << SECTOR_SHIFT);
      mutex_unlock(&md->suspended_bdev->bd_inode->i_mutex);
}

static int __bind(struct mapped_device *md, struct dm_table *t)
{
      struct request_queue *q = md->queue;
      sector_t size;

      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));

      if (md->suspended_bdev)
            __set_size(md, size);
      if (size == 0)
            return 0;

      dm_table_get(t);
      dm_table_event_callback(t, event_callback, md);

      write_lock(&md->map_lock);
      md->map = t;
      dm_table_set_restrictions(t, q);
      write_unlock(&md->map_lock);

      return 0;
}

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

      if (!map)
            return;

      dm_table_event_callback(map, NULL, NULL);
      write_lock(&md->map_lock);
      md->map = NULL;
      write_unlock(&md->map_lock);
      dm_table_put(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;

      *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 ||
               (dm_disk(md)->first_minor != 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, dm_disk(md)->first_minor);
            set_bit(DMF_FREEING, &md->flags);
            spin_unlock(&_minor_lock);
            if (!dm_suspended(md)) {
                  dm_table_presuspend_targets(map);
                  dm_table_postsuspend_targets(map);
            }
            __unbind(md);
            dm_table_put(map);
            free_dev(md);
      }
}
EXPORT_SYMBOL_GPL(dm_put);

/*
 * Process the deferred bios
 */
static void __flush_deferred_io(struct mapped_device *md, struct bio *c)
{
      struct bio *n;

      while (c) {
            n = c->bi_next;
            c->bi_next = NULL;
            if (__split_bio(md, c))
                  bio_io_error(c);
            c = n;
      }
}

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

      down(&md->suspend_lock);

      /* device must be suspended */
      if (!dm_suspended(md))
            goto out;

      /* without bdev, the device size cannot be changed */
      if (!md->suspended_bdev)
            if (get_capacity(md->disk) != dm_table_get_size(table))
                  goto out;

      __unbind(md);
      r = __bind(md, table);

out:
      up(&md->suspend_lock);
      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->suspended_bdev);
      if (IS_ERR(md->frozen_sb)) {
            r = PTR_ERR(md->frozen_sb);
            md->frozen_sb = NULL;
            return r;
      }

      set_bit(DMF_FROZEN, &md->flags);

      /* don't bdput right now, we don't want the bdev
       * to go away while it is locked.
       */
      return 0;
}

static void unlock_fs(struct mapped_device *md)
{
      if (!test_bit(DMF_FROZEN, &md->flags))
            return;

      thaw_bdev(md->suspended_bdev, md->frozen_sb);
      md->frozen_sb = NULL;
      clear_bit(DMF_FROZEN, &md->flags);
}

/*
 * We need to be able to change a mapping table under a mounted
 * filesystem.  For example we might want to move some data in
 * the background.  Before the table can be swapped with
 * dm_bind_table, dm_suspend must be called to flush any in
 * flight bios and ensure that any further io gets deferred.
 */
int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
{
      struct dm_table *map = NULL;
      unsigned long flags;
      DECLARE_WAITQUEUE(wait, current);
      struct bio *def;
      int r = -EINVAL;
      int do_lockfs = suspend_flags & DM_SUSPEND_LOCKFS_FLAG ? 1 : 0;
      int noflush = suspend_flags & DM_SUSPEND_NOFLUSH_FLAG ? 1 : 0;

      down(&md->suspend_lock);

      if (dm_suspended(md))
            goto out_unlock;

      map = dm_get_table(md);

      /*
       * DMF_NOFLUSH_SUSPENDING must be set before presuspend.
       * This flag is cleared before dm_suspend returns.
       */
      if (noflush)
            set_bit(DMF_NOFLUSH_SUSPENDING, &md->flags);

      /* This does not get reverted if there's an error later. */
      dm_table_presuspend_targets(map);

      /* bdget() can stall if the pending I/Os are not flushed */
      if (!noflush) {
            md->suspended_bdev = bdget_disk(md->disk, 0);
            if (!md->suspended_bdev) {
                  DMWARN("bdget failed in dm_suspend");
                  r = -ENOMEM;
                  goto flush_and_out;
            }
      }

      /*
       * Flush I/O to the device.
       * noflush supersedes do_lockfs, because lock_fs() needs to flush I/Os.
       */
      if (do_lockfs && !noflush) {
            r = lock_fs(md);
            if (r)
                  goto out;
      }

      /*
       * First we set the BLOCK_IO flag so no more ios will be mapped.
       */
      down_write(&md->io_lock);
      set_bit(DMF_BLOCK_IO, &md->flags);

      add_wait_queue(&md->wait, &wait);
      up_write(&md->io_lock);

      /* unplug */
      if (map)
            dm_table_unplug_all(map);

      /*
       * Then we wait for the already mapped ios to
       * complete.
       */
      while (1) {
            set_current_state(TASK_INTERRUPTIBLE);

            if (!atomic_read(&md->pending) || signal_pending(current))
                  break;

            io_schedule();
      }
      set_current_state(TASK_RUNNING);

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

      if (noflush) {
            spin_lock_irqsave(&md->pushback_lock, flags);
            clear_bit(DMF_NOFLUSH_SUSPENDING, &md->flags);
            bio_list_merge_head(&md->deferred, &md->pushback);
            bio_list_init(&md->pushback);
            spin_unlock_irqrestore(&md->pushback_lock, flags);
      }

      /* were we interrupted ? */
      r = -EINTR;
      if (atomic_read(&md->pending)) {
            clear_bit(DMF_BLOCK_IO, &md->flags);
            def = bio_list_get(&md->deferred);
            __flush_deferred_io(md, def);
            up_write(&md->io_lock);
            unlock_fs(md);
            goto out; /* pushback list is already flushed, so skip flush */
      }
      up_write(&md->io_lock);

      dm_table_postsuspend_targets(map);

      set_bit(DMF_SUSPENDED, &md->flags);

      r = 0;

flush_and_out:
      if (r && noflush) {
            /*
             * Because there may be already I/Os in the pushback list,
             * flush them before return.
             */
            down_write(&md->io_lock);

            spin_lock_irqsave(&md->pushback_lock, flags);
            clear_bit(DMF_NOFLUSH_SUSPENDING, &md->flags);
            bio_list_merge_head(&md->deferred, &md->pushback);
            bio_list_init(&md->pushback);
            spin_unlock_irqrestore(&md->pushback_lock, flags);

            def = bio_list_get(&md->deferred);
            __flush_deferred_io(md, def);
            up_write(&md->io_lock);
      }

out:
      if (r && md->suspended_bdev) {
            bdput(md->suspended_bdev);
            md->suspended_bdev = NULL;
      }

      dm_table_put(map);

out_unlock:
      up(&md->suspend_lock);
      return r;
}

int dm_resume(struct mapped_device *md)
{
      int r = -EINVAL;
      struct bio *def;
      struct dm_table *map = NULL;

      down(&md->suspend_lock);
      if (!dm_suspended(md))
            goto out;

      map = dm_get_table(md);
      if (!map || !dm_table_get_size(map))
            goto out;

      r = dm_table_resume_targets(map);
      if (r)
            goto out;

      down_write(&md->io_lock);
      clear_bit(DMF_BLOCK_IO, &md->flags);

      def = bio_list_get(&md->deferred);
      __flush_deferred_io(md, def);
      up_write(&md->io_lock);

      unlock_fs(md);

      if (md->suspended_bdev) {
            bdput(md->suspended_bdev);
            md->suspended_bdev = NULL;
      }

      clear_bit(DMF_SUSPENDED, &md->flags);

      dm_table_unplug_all(map);

      dm_kobject_uevent(md);

      r = 0;

out:
      dm_table_put(map);
      up(&md->suspend_lock);

      return r;
}

/*-----------------------------------------------------------------
 * Event notification.
 *---------------------------------------------------------------*/
void dm_kobject_uevent(struct mapped_device *md)
{
      kobject_uevent(&md->disk->kobj, KOBJ_CHANGE);
}

uint32_t dm_next_uevent_seq(struct mapped_device *md)
{
      return atomic_add_return(1, &md->uevent_seq);
}

uint32_t dm_get_event_nr(struct mapped_device *md)
{
      return atomic_read(&md->event_nr);
}

int dm_wait_event(struct mapped_device *md, int event_nr)
{
      return wait_event_interruptible(md->eventq,
                  (event_nr != atomic_read(&md->event_nr)));
}

void dm_uevent_add(struct mapped_device *md, struct list_head *elist)
{
      unsigned long flags;

      spin_lock_irqsave(&md->uevent_lock, flags);
      list_add(elist, &md->uevent_list);
      spin_unlock_irqrestore(&md->uevent_lock, flags);
}

/*
 * The gendisk is only valid as long as you have a reference
 * count on 'md'.
 */
struct gendisk *dm_disk(struct mapped_device *md)
{
      return md->disk;
}

int dm_suspended(struct mapped_device *md)
{
      return test_bit(DMF_SUSPENDED, &md->flags);
}

int dm_noflush_suspending(struct dm_target *ti)
{
      struct mapped_device *md = dm_table_get_md(ti->table);
      int r = __noflush_suspending(md);

      dm_put(md);

      return r;
}
EXPORT_SYMBOL_GPL(dm_noflush_suspending);

static struct block_device_operations dm_blk_dops = {
      .open = dm_blk_open,
      .release = dm_blk_close,
      .ioctl = dm_blk_ioctl,
      .getgeo = dm_blk_getgeo,
      .owner = THIS_MODULE
};

EXPORT_SYMBOL(dm_get_mapinfo);

/*
 * module hooks
 */
module_init(dm_init);
module_exit(dm_exit);

module_param(major, uint, 0);
MODULE_PARM_DESC(major, "The major number of the device mapper");
MODULE_DESCRIPTION(DM_NAME " driver");
MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
MODULE_LICENSE("GPL");

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