dm-thin.c

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/*
 * Copyright (C) 2011-2012 Red Hat UK.
 *
 * This file is released under the GPL.
 */

#include "dm-thin-metadata.h"
#include "dm-bio-prison.h"
#include "dm.h"

#include <linux/device-mapper.h>
#include <linux/dm-io.h>
#include <linux/dm-kcopyd.h>
#include <linux/list.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>

#define DM_MSG_PREFIX   "thin"

/*
 * Tunable constants
 */
#define ENDIO_HOOK_POOL_SIZE 1024
#define MAPPING_POOL_SIZE 1024
#define PRISON_CELLS 1024
#define COMMIT_PERIOD HZ

/*
 * The block size of the device holding pool data must be
 * between 64KB and 1GB.
 */
#define DATA_DEV_BLOCK_SIZE_MIN_SECTORS (64 * 1024 >> SECTOR_SHIFT)
#define DATA_DEV_BLOCK_SIZE_MAX_SECTORS (1024 * 1024 * 1024 >> SECTOR_SHIFT)

/*
 * Device id is restricted to 24 bits.
 */
#define MAX_DEV_ID ((1 << 24) - 1)

/*
 * How do we handle breaking sharing of data blocks?
 * =================================================
 *
 * We use a standard copy-on-write btree to store the mappings for the
 * devices (note I'm talking about copy-on-write of the metadata here, not
 * the data).  When you take an internal snapshot you clone the root node
 * of the origin btree.  After this there is no concept of an origin or a
 * snapshot.  They are just two device trees that happen to point to the
 * same data blocks.
 *
 * When we get a write in we decide if it's to a shared data block using
 * some timestamp magic.  If it is, we have to break sharing.
 *
 * Let's say we write to a shared block in what was the origin.  The
 * steps are:
 *
 * i) plug io further to this physical block. (see bio_prison code).
 *
 * ii) quiesce any read io to that shared data block.  Obviously
 * including all devices that share this block.  (see dm_deferred_set code)
 *
 * iii) copy the data block to a newly allocate block.  This step can be
 * missed out if the io covers the block. (schedule_copy).
 *
 * iv) insert the new mapping into the origin's btree
 * (process_prepared_mapping).  This act of inserting breaks some
 * sharing of btree nodes between the two devices.  Breaking sharing only
 * effects the btree of that specific device.  Btrees for the other
 * devices that share the block never change.  The btree for the origin
 * device as it was after the last commit is untouched, ie. we're using
 * persistent data structures in the functional programming sense.
 *
 * v) unplug io to this physical block, including the io that triggered
 * the breaking of sharing.
 *
 * Steps (ii) and (iii) occur in parallel.
 *
 * The metadata _doesn't_ need to be committed before the io continues.  We
 * get away with this because the io is always written to a _new_ block.
 * If there's a crash, then:
 *
 * - The origin mapping will point to the old origin block (the shared
 * one).  This will contain the data as it was before the io that triggered
 * the breaking of sharing came in.
 *
 * - The snap mapping still points to the old block.  As it would after
 * the commit.
 *
 * The downside of this scheme is the timestamp magic isn't perfect, and
 * will continue to think that data block in the snapshot device is shared
 * even after the write to the origin has broken sharing.  I suspect data
 * blocks will typically be shared by many different devices, so we're
 * breaking sharing n + 1 times, rather than n, where n is the number of
 * devices that reference this data block.  At the moment I think the
 * benefits far, far outweigh the disadvantages.
 */

/*----------------------------------------------------------------*/

/*
 * Key building.
 */
static void build_data_key(struct dm_thin_device *td,
               dm_block_t b, struct dm_cell_key *key)
{
    key->virtual = 0;
    key->dev = dm_thin_dev_id(td);
    key->block = b;
}

static void build_virtual_key(struct dm_thin_device *td, dm_block_t b,
                  struct dm_cell_key *key)
{
    key->virtual = 1;
    key->dev = dm_thin_dev_id(td);
    key->block = b;
}

/*----------------------------------------------------------------*/

/*
 * A pool device ties together a metadata device and a data device.  It
 * also provides the interface for creating and destroying internal
 * devices.
 */
struct dm_thin_new_mapping;

/*
 * The pool runs in 3 modes.  Ordered in degraded order for comparisons.
 */
enum pool_mode {
    PM_WRITE,       /* metadata may be changed */
    PM_READ_ONLY,       /* metadata may not be changed */
    PM_FAIL,        /* all I/O fails */
};

struct pool_features {
    enum pool_mode mode;

    bool zero_new_blocks:1;
    bool discard_enabled:1;
    bool discard_passdown:1;
};

struct thin_c;
typedef void (*process_bio_fn)(struct thin_c *tc, struct bio *bio);
typedef void (*process_mapping_fn)(struct dm_thin_new_mapping *m);

struct pool {
    struct list_head list;
    struct dm_target *ti;   /* Only set if a pool target is bound */

    struct mapped_device *pool_md;
    struct block_device *md_dev;
    struct dm_pool_metadata *pmd;

    dm_block_t low_water_blocks;
    uint32_t sectors_per_block;
    int sectors_per_block_shift;

    struct pool_features pf;
    unsigned low_water_triggered:1; /* A dm event has been sent */
    unsigned no_free_space:1;   /* A -ENOSPC warning has been issued */

    struct dm_bio_prison *prison;
    struct dm_kcopyd_client *copier;

    struct workqueue_struct *wq;
    struct work_struct worker;
    struct delayed_work waker;

    unsigned long last_commit_jiffies;
    unsigned ref_count;

    spinlock_t lock;
    struct bio_list deferred_bios;
    struct bio_list deferred_flush_bios;
    struct list_head prepared_mappings;
    struct list_head prepared_discards;

    struct bio_list retry_on_resume_list;

    struct dm_deferred_set *shared_read_ds;
    struct dm_deferred_set *all_io_ds;

    struct dm_thin_new_mapping *next_mapping;
    mempool_t *mapping_pool;
    mempool_t *endio_hook_pool;

    process_bio_fn process_bio;
    process_bio_fn process_discard;

    process_mapping_fn process_prepared_mapping;
    process_mapping_fn process_prepared_discard;
};

static enum pool_mode get_pool_mode(struct pool *pool);
static void set_pool_mode(struct pool *pool, enum pool_mode mode);

/*
 * Target context for a pool.
 */
struct pool_c {
    struct dm_target *ti;
    struct pool *pool;
    struct dm_dev *data_dev;
    struct dm_dev *metadata_dev;
    struct dm_target_callbacks callbacks;

    dm_block_t low_water_blocks;
    struct pool_features requested_pf; /* Features requested during table load */
    struct pool_features adjusted_pf;  /* Features used after adjusting for constituent devices */
};

/*
 * Target context for a thin.
 */
struct thin_c {
    struct dm_dev *pool_dev;
    struct dm_dev *origin_dev;
    dm_thin_id dev_id;

    struct pool *pool;
    struct dm_thin_device *td;
};

/*----------------------------------------------------------------*/

/*
 * A global list of pools that uses a struct mapped_device as a key.
 */
static struct dm_thin_pool_table {
    struct mutex mutex;
    struct list_head pools;
} dm_thin_pool_table;

static void pool_table_init(void)
{
    mutex_init(&dm_thin_pool_table.mutex);
    INIT_LIST_HEAD(&dm_thin_pool_table.pools);
}

static void __pool_table_insert(struct pool *pool)
{
    BUG_ON(!mutex_is_locked(&dm_thin_pool_table.mutex));
    list_add(&pool->list, &dm_thin_pool_table.pools);
}

static void __pool_table_remove(struct pool *pool)
{
    BUG_ON(!mutex_is_locked(&dm_thin_pool_table.mutex));
    list_del(&pool->list);
}

static struct pool *__pool_table_lookup(struct mapped_device *md)
{
    struct pool *pool = NULL, *tmp;

    BUG_ON(!mutex_is_locked(&dm_thin_pool_table.mutex));

    list_for_each_entry(tmp, &dm_thin_pool_table.pools, list) {
        if (tmp->pool_md == md) {
            pool = tmp;
            break;
        }
    }

    return pool;
}

static struct pool *__pool_table_lookup_metadata_dev(struct block_device *md_dev)
{
    struct pool *pool = NULL, *tmp;

    BUG_ON(!mutex_is_locked(&dm_thin_pool_table.mutex));

    list_for_each_entry(tmp, &dm_thin_pool_table.pools, list) {
        if (tmp->md_dev == md_dev) {
            pool = tmp;
            break;
        }
    }

    return pool;
}

/*----------------------------------------------------------------*/

struct dm_thin_endio_hook {
    struct thin_c *tc;
    struct dm_deferred_entry *shared_read_entry;
    struct dm_deferred_entry *all_io_entry;
    struct dm_thin_new_mapping *overwrite_mapping;
};

static void __requeue_bio_list(struct thin_c *tc, struct bio_list *master)
{
    struct bio *bio;
    struct bio_list bios;

    bio_list_init(&bios);
    bio_list_merge(&bios, master);
    bio_list_init(master);

    while ((bio = bio_list_pop(&bios))) {
        struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;

        if (h->tc == tc)
            bio_endio(bio, DM_ENDIO_REQUEUE);
        else
            bio_list_add(master, bio);
    }
}

static void requeue_io(struct thin_c *tc)
{
    struct pool *pool = tc->pool;
    unsigned long flags;

    spin_lock_irqsave(&pool->lock, flags);
    __requeue_bio_list(tc, &pool->deferred_bios);
    __requeue_bio_list(tc, &pool->retry_on_resume_list);
    spin_unlock_irqrestore(&pool->lock, flags);
}

/*
 * This section of code contains the logic for processing a thin device's IO.
 * Much of the code depends on pool object resources (lists, workqueues, etc)
 * but most is exclusively called from the thin target rather than the thin-pool
 * target.
 */

static dm_block_t get_bio_block(struct thin_c *tc, struct bio *bio)
{
    sector_t block_nr = bio->bi_sector;

    if (tc->pool->sectors_per_block_shift < 0)
        (void) sector_div(block_nr, tc->pool->sectors_per_block);
    else
        block_nr >>= tc->pool->sectors_per_block_shift;

    return block_nr;
}

static void remap(struct thin_c *tc, struct bio *bio, dm_block_t block)
{
    struct pool *pool = tc->pool;
    sector_t bi_sector = bio->bi_sector;

    bio->bi_bdev = tc->pool_dev->bdev;
    if (tc->pool->sectors_per_block_shift < 0)
        bio->bi_sector = (block * pool->sectors_per_block) +
                 sector_div(bi_sector, pool->sectors_per_block);
    else
        bio->bi_sector = (block << pool->sectors_per_block_shift) |
                (bi_sector & (pool->sectors_per_block - 1));
}

static void remap_to_origin(struct thin_c *tc, struct bio *bio)
{
    bio->bi_bdev = tc->origin_dev->bdev;
}

static int bio_triggers_commit(struct thin_c *tc, struct bio *bio)
{
    return (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) &&
        dm_thin_changed_this_transaction(tc->td);
}

static void issue(struct thin_c *tc, struct bio *bio)
{
    struct pool *pool = tc->pool;
    unsigned long flags;

    if (!bio_triggers_commit(tc, bio)) {
        generic_make_request(bio);
        return;
    }

    /*
     * Complete bio with an error if earlier I/O caused changes to
     * the metadata that can't be committed e.g, due to I/O errors
     * on the metadata device.
     */
    if (dm_thin_aborted_changes(tc->td)) {
        bio_io_error(bio);
        return;
    }

    /*
     * Batch together any bios that trigger commits and then issue a
     * single commit for them in process_deferred_bios().
     */
    spin_lock_irqsave(&pool->lock, flags);
    bio_list_add(&pool->deferred_flush_bios, bio);
    spin_unlock_irqrestore(&pool->lock, flags);
}

static void remap_to_origin_and_issue(struct thin_c *tc, struct bio *bio)
{
    remap_to_origin(tc, bio);
    issue(tc, bio);
}

static void remap_and_issue(struct thin_c *tc, struct bio *bio,
                dm_block_t block)
{
    remap(tc, bio, block);
    issue(tc, bio);
}

/*
 * wake_worker() is used when new work is queued and when pool_resume is
 * ready to continue deferred IO processing.
 */
static void wake_worker(struct pool *pool)
{
    queue_work(pool->wq, &pool->worker);
}

/*----------------------------------------------------------------*/

/*
 * Bio endio functions.
 */
struct dm_thin_new_mapping {
    struct list_head list;

    unsigned quiesced:1;
    unsigned prepared:1;
    unsigned pass_discard:1;

    struct thin_c *tc;
    dm_block_t virt_block;
    dm_block_t data_block;
    struct dm_bio_prison_cell *cell, *cell2;
    int err;

    /*
     * If the bio covers the whole area of a block then we can avoid
     * zeroing or copying.  Instead this bio is hooked.  The bio will
     * still be in the cell, so care has to be taken to avoid issuing
     * the bio twice.
     */
    struct bio *bio;
    bio_end_io_t *saved_bi_end_io;
};

static void __maybe_add_mapping(struct dm_thin_new_mapping *m)
{
    struct pool *pool = m->tc->pool;

    if (m->quiesced && m->prepared) {
        list_add(&m->list, &pool->prepared_mappings);
        wake_worker(pool);
    }
}

static void copy_complete(int read_err, unsigned long write_err, void *context)
{
    unsigned long flags;
    struct dm_thin_new_mapping *m = context;
    struct pool *pool = m->tc->pool;

    m->err = read_err || write_err ? -EIO : 0;

    spin_lock_irqsave(&pool->lock, flags);
    m->prepared = 1;
    __maybe_add_mapping(m);
    spin_unlock_irqrestore(&pool->lock, flags);
}

static void overwrite_endio(struct bio *bio, int err)
{
    unsigned long flags;
    struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;
    struct dm_thin_new_mapping *m = h->overwrite_mapping;
    struct pool *pool = m->tc->pool;

    m->err = err;

    spin_lock_irqsave(&pool->lock, flags);
    m->prepared = 1;
    __maybe_add_mapping(m);
    spin_unlock_irqrestore(&pool->lock, flags);
}

/*----------------------------------------------------------------*/

/*
 * Workqueue.
 */

/*
 * Prepared mapping jobs.
 */

/*
 * This sends the bios in the cell back to the deferred_bios list.
 */
static void cell_defer(struct thin_c *tc, struct dm_bio_prison_cell *cell,
               dm_block_t data_block)
{
    struct pool *pool = tc->pool;
    unsigned long flags;

    spin_lock_irqsave(&pool->lock, flags);
    dm_cell_release(cell, &pool->deferred_bios);
    spin_unlock_irqrestore(&tc->pool->lock, flags);

    wake_worker(pool);
}

/*
 * Same as cell_defer above, except it omits one particular detainee,
 * a write bio that covers the block and has already been processed.
 */
static void cell_defer_except(struct thin_c *tc, struct dm_bio_prison_cell *cell)
{
    struct bio_list bios;
    struct pool *pool = tc->pool;
    unsigned long flags;

    bio_list_init(&bios);

    spin_lock_irqsave(&pool->lock, flags);
    dm_cell_release_no_holder(cell, &pool->deferred_bios);
    spin_unlock_irqrestore(&pool->lock, flags);

    wake_worker(pool);
}

static void process_prepared_mapping_fail(struct dm_thin_new_mapping *m)
{
    if (m->bio)
        m->bio->bi_end_io = m->saved_bi_end_io;
    dm_cell_error(m->cell);
    list_del(&m->list);
    mempool_free(m, m->tc->pool->mapping_pool);
}
static void process_prepared_mapping(struct dm_thin_new_mapping *m)
{
    struct thin_c *tc = m->tc;
    struct bio *bio;
    int r;

    bio = m->bio;
    if (bio)
        bio->bi_end_io = m->saved_bi_end_io;

    if (m->err) {
        dm_cell_error(m->cell);
        goto out;
    }

    /*
     * Commit the prepared block into the mapping btree.
     * Any I/O for this block arriving after this point will get
     * remapped to it directly.
     */
    r = dm_thin_insert_block(tc->td, m->virt_block, m->data_block);
    if (r) {
        DMERR("dm_thin_insert_block() failed");
        dm_cell_error(m->cell);
        goto out;
    }

    /*
     * Release any bios held while the block was being provisioned.
     * If we are processing a write bio that completely covers the block,
     * we already processed it so can ignore it now when processing
     * the bios in the cell.
     */
    if (bio) {
        cell_defer_except(tc, m->cell);
        bio_endio(bio, 0);
    } else
        cell_defer(tc, m->cell, m->data_block);

out:
    list_del(&m->list);
    mempool_free(m, tc->pool->mapping_pool);
}

static void process_prepared_discard_fail(struct dm_thin_new_mapping *m)
{
    struct thin_c *tc = m->tc;

    bio_io_error(m->bio);
    cell_defer_except(tc, m->cell);
    cell_defer_except(tc, m->cell2);
    mempool_free(m, tc->pool->mapping_pool);
}

static void process_prepared_discard_passdown(struct dm_thin_new_mapping *m)
{
    struct thin_c *tc = m->tc;

    if (m->pass_discard)
        remap_and_issue(tc, m->bio, m->data_block);
    else
        bio_endio(m->bio, 0);

    cell_defer_except(tc, m->cell);
    cell_defer_except(tc, m->cell2);
    mempool_free(m, tc->pool->mapping_pool);
}

static void process_prepared_discard(struct dm_thin_new_mapping *m)
{
    int r;
    struct thin_c *tc = m->tc;

    r = dm_thin_remove_block(tc->td, m->virt_block);
    if (r)
        DMERR("dm_thin_remove_block() failed");

    process_prepared_discard_passdown(m);
}

static void process_prepared(struct pool *pool, struct list_head *head,
                 process_mapping_fn *fn)
{
    unsigned long flags;
    struct list_head maps;
    struct dm_thin_new_mapping *m, *tmp;

    INIT_LIST_HEAD(&maps);
    spin_lock_irqsave(&pool->lock, flags);
    list_splice_init(head, &maps);
    spin_unlock_irqrestore(&pool->lock, flags);

    list_for_each_entry_safe(m, tmp, &maps, list)
        (*fn)(m);
}

/*
 * Deferred bio jobs.
 */
static int io_overlaps_block(struct pool *pool, struct bio *bio)
{
    return bio->bi_size == (pool->sectors_per_block << SECTOR_SHIFT);
}

static int io_overwrites_block(struct pool *pool, struct bio *bio)
{
    return (bio_data_dir(bio) == WRITE) &&
        io_overlaps_block(pool, bio);
}

static void save_and_set_endio(struct bio *bio, bio_end_io_t **save,
                   bio_end_io_t *fn)
{
    *save = bio->bi_end_io;
    bio->bi_end_io = fn;
}

static int ensure_next_mapping(struct pool *pool)
{
    if (pool->next_mapping)
        return 0;

    pool->next_mapping = mempool_alloc(pool->mapping_pool, GFP_ATOMIC);

    return pool->next_mapping ? 0 : -ENOMEM;
}

static struct dm_thin_new_mapping *get_next_mapping(struct pool *pool)
{
    struct dm_thin_new_mapping *r = pool->next_mapping;

    BUG_ON(!pool->next_mapping);

    pool->next_mapping = NULL;

    return r;
}

static void schedule_copy(struct thin_c *tc, dm_block_t virt_block,
              struct dm_dev *origin, dm_block_t data_origin,
              dm_block_t data_dest,
              struct dm_bio_prison_cell *cell, struct bio *bio)
{
    int r;
    struct pool *pool = tc->pool;
    struct dm_thin_new_mapping *m = get_next_mapping(pool);

    INIT_LIST_HEAD(&m->list);
    m->quiesced = 0;
    m->prepared = 0;
    m->tc = tc;
    m->virt_block = virt_block;
    m->data_block = data_dest;
    m->cell = cell;
    m->err = 0;
    m->bio = NULL;

    if (!dm_deferred_set_add_work(pool->shared_read_ds, &m->list))
        m->quiesced = 1;

    /*
     * IO to pool_dev remaps to the pool target's data_dev.
     *
     * If the whole block of data is being overwritten, we can issue the
     * bio immediately. Otherwise we use kcopyd to clone the data first.
     */
    if (io_overwrites_block(pool, bio)) {
        struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;

        h->overwrite_mapping = m;
        m->bio = bio;
        save_and_set_endio(bio, &m->saved_bi_end_io, overwrite_endio);
        remap_and_issue(tc, bio, data_dest);
    } else {
        struct dm_io_region from, to;

        from.bdev = origin->bdev;
        from.sector = data_origin * pool->sectors_per_block;
        from.count = pool->sectors_per_block;

        to.bdev = tc->pool_dev->bdev;
        to.sector = data_dest * pool->sectors_per_block;
        to.count = pool->sectors_per_block;

        r = dm_kcopyd_copy(pool->copier, &from, 1, &to,
                   0, copy_complete, m);
        if (r < 0) {
            mempool_free(m, pool->mapping_pool);
            DMERR("dm_kcopyd_copy() failed");
            dm_cell_error(cell);
        }
    }
}

static void schedule_internal_copy(struct thin_c *tc, dm_block_t virt_block,
                   dm_block_t data_origin, dm_block_t data_dest,
                   struct dm_bio_prison_cell *cell, struct bio *bio)
{
    schedule_copy(tc, virt_block, tc->pool_dev,
              data_origin, data_dest, cell, bio);
}

static void schedule_external_copy(struct thin_c *tc, dm_block_t virt_block,
                   dm_block_t data_dest,
                   struct dm_bio_prison_cell *cell, struct bio *bio)
{
    schedule_copy(tc, virt_block, tc->origin_dev,
              virt_block, data_dest, cell, bio);
}

static void schedule_zero(struct thin_c *tc, dm_block_t virt_block,
              dm_block_t data_block, struct dm_bio_prison_cell *cell,
              struct bio *bio)
{
    struct pool *pool = tc->pool;
    struct dm_thin_new_mapping *m = get_next_mapping(pool);

    INIT_LIST_HEAD(&m->list);
    m->quiesced = 1;
    m->prepared = 0;
    m->tc = tc;
    m->virt_block = virt_block;
    m->data_block = data_block;
    m->cell = cell;
    m->err = 0;
    m->bio = NULL;

    /*
     * If the whole block of data is being overwritten or we are not
     * zeroing pre-existing data, we can issue the bio immediately.
     * Otherwise we use kcopyd to zero the data first.
     */
    if (!pool->pf.zero_new_blocks)
        process_prepared_mapping(m);

    else if (io_overwrites_block(pool, bio)) {
        struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;

        h->overwrite_mapping = m;
        m->bio = bio;
        save_and_set_endio(bio, &m->saved_bi_end_io, overwrite_endio);
        remap_and_issue(tc, bio, data_block);
    } else {
        int r;
        struct dm_io_region to;

        to.bdev = tc->pool_dev->bdev;
        to.sector = data_block * pool->sectors_per_block;
        to.count = pool->sectors_per_block;

        r = dm_kcopyd_zero(pool->copier, 1, &to, 0, copy_complete, m);
        if (r < 0) {
            mempool_free(m, pool->mapping_pool);
            DMERR("dm_kcopyd_zero() failed");
            dm_cell_error(cell);
        }
    }
}

static int commit(struct pool *pool)
{
    int r;

    r = dm_pool_commit_metadata(pool->pmd);
    if (r)
        DMERR("commit failed, error = %d", r);

    return r;
}

/*
 * A non-zero return indicates read_only or fail_io mode.
 * Many callers don't care about the return value.
 */
static int commit_or_fallback(struct pool *pool)
{
    int r;

    if (get_pool_mode(pool) != PM_WRITE)
        return -EINVAL;

    r = commit(pool);
    if (r)
        set_pool_mode(pool, PM_READ_ONLY);

    return r;
}

static int alloc_data_block(struct thin_c *tc, dm_block_t *result)
{
    int r;
    dm_block_t free_blocks;
    unsigned long flags;
    struct pool *pool = tc->pool;

    r = dm_pool_get_free_block_count(pool->pmd, &free_blocks);
    if (r)
        return r;

    if (free_blocks <= pool->low_water_blocks && !pool->low_water_triggered) {
        DMWARN("%s: reached low water mark, sending event.",
               dm_device_name(pool->pool_md));
        spin_lock_irqsave(&pool->lock, flags);
        pool->low_water_triggered = 1;
        spin_unlock_irqrestore(&pool->lock, flags);
        dm_table_event(pool->ti->table);
    }

    if (!free_blocks) {
        if (pool->no_free_space)
            return -ENOSPC;
        else {
            /*
             * Try to commit to see if that will free up some
             * more space.
             */
            (void) commit_or_fallback(pool);

            r = dm_pool_get_free_block_count(pool->pmd, &free_blocks);
            if (r)
                return r;

            /*
             * If we still have no space we set a flag to avoid
             * doing all this checking and return -ENOSPC.
             */
            if (!free_blocks) {
                DMWARN("%s: no free space available.",
                       dm_device_name(pool->pool_md));
                spin_lock_irqsave(&pool->lock, flags);
                pool->no_free_space = 1;
                spin_unlock_irqrestore(&pool->lock, flags);
                return -ENOSPC;
            }
        }
    }

    r = dm_pool_alloc_data_block(pool->pmd, result);
    if (r)
        return r;

    return 0;
}

/*
 * If we have run out of space, queue bios until the device is
 * resumed, presumably after having been reloaded with more space.
 */
static void retry_on_resume(struct bio *bio)
{
    struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;
    struct thin_c *tc = h->tc;
    struct pool *pool = tc->pool;
    unsigned long flags;

    spin_lock_irqsave(&pool->lock, flags);
    bio_list_add(&pool->retry_on_resume_list, bio);
    spin_unlock_irqrestore(&pool->lock, flags);
}

static void no_space(struct dm_bio_prison_cell *cell)
{
    struct bio *bio;
    struct bio_list bios;

    bio_list_init(&bios);
    dm_cell_release(cell, &bios);

    while ((bio = bio_list_pop(&bios)))
        retry_on_resume(bio);
}

static void process_discard(struct thin_c *tc, struct bio *bio)
{
    int r;
    unsigned long flags;
    struct pool *pool = tc->pool;
    struct dm_bio_prison_cell *cell, *cell2;
    struct dm_cell_key key, key2;
    dm_block_t block = get_bio_block(tc, bio);
    struct dm_thin_lookup_result lookup_result;
    struct dm_thin_new_mapping *m;

    build_virtual_key(tc->td, block, &key);
    if (dm_bio_detain(tc->pool->prison, &key, bio, &cell))
        return;

    r = dm_thin_find_block(tc->td, block, 1, &lookup_result);
    switch (r) {
    case 0:
        /*
         * Check nobody is fiddling with this pool block.  This can
         * happen if someone's in the process of breaking sharing
         * on this block.
         */
        build_data_key(tc->td, lookup_result.block, &key2);
        if (dm_bio_detain(tc->pool->prison, &key2, bio, &cell2)) {
            dm_cell_release_singleton(cell, bio);
            break;
        }

        if (io_overlaps_block(pool, bio)) {
            /*
             * IO may still be going to the destination block.  We must
             * quiesce before we can do the removal.
             */
            m = get_next_mapping(pool);
            m->tc = tc;
            m->pass_discard = (!lookup_result.shared) && pool->pf.discard_passdown;
            m->virt_block = block;
            m->data_block = lookup_result.block;
            m->cell = cell;
            m->cell2 = cell2;
            m->err = 0;
            m->bio = bio;

            if (!dm_deferred_set_add_work(pool->all_io_ds, &m->list)) {
                spin_lock_irqsave(&pool->lock, flags);
                list_add(&m->list, &pool->prepared_discards);
                spin_unlock_irqrestore(&pool->lock, flags);
                wake_worker(pool);
            }
        } else {
            /*
             * The DM core makes sure that the discard doesn't span
             * a block boundary.  So we submit the discard of a
             * partial block appropriately.
             */
            dm_cell_release_singleton(cell, bio);
            dm_cell_release_singleton(cell2, bio);
            if ((!lookup_result.shared) && pool->pf.discard_passdown)
                remap_and_issue(tc, bio, lookup_result.block);
            else
                bio_endio(bio, 0);
        }
        break;

    case -ENODATA:
        /*
         * It isn't provisioned, just forget it.
         */
        dm_cell_release_singleton(cell, bio);
        bio_endio(bio, 0);
        break;

    default:
        DMERR("discard: find block unexpectedly returned %d", r);
        dm_cell_release_singleton(cell, bio);
        bio_io_error(bio);
        break;
    }
}

static void break_sharing(struct thin_c *tc, struct bio *bio, dm_block_t block,
              struct dm_cell_key *key,
              struct dm_thin_lookup_result *lookup_result,
              struct dm_bio_prison_cell *cell)
{
    int r;
    dm_block_t data_block;

    r = alloc_data_block(tc, &data_block);
    switch (r) {
    case 0:
        schedule_internal_copy(tc, block, lookup_result->block,
                       data_block, cell, bio);
        break;

    case -ENOSPC:
        no_space(cell);
        break;

    default:
        DMERR("%s: alloc_data_block() failed, error = %d", __func__, r);
        dm_cell_error(cell);
        break;
    }
}

static void process_shared_bio(struct thin_c *tc, struct bio *bio,
                   dm_block_t block,
                   struct dm_thin_lookup_result *lookup_result)
{
    struct dm_bio_prison_cell *cell;
    struct pool *pool = tc->pool;
    struct dm_cell_key key;

    /*
     * If cell is already occupied, then sharing is already in the process
     * of being broken so we have nothing further to do here.
     */
    build_data_key(tc->td, lookup_result->block, &key);
    if (dm_bio_detain(pool->prison, &key, bio, &cell))
        return;

    if (bio_data_dir(bio) == WRITE && bio->bi_size)
        break_sharing(tc, bio, block, &key, lookup_result, cell);
    else {
        struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;

        h->shared_read_entry = dm_deferred_entry_inc(pool->shared_read_ds);

        dm_cell_release_singleton(cell, bio);
        remap_and_issue(tc, bio, lookup_result->block);
    }
}

static void provision_block(struct thin_c *tc, struct bio *bio, dm_block_t block,
                struct dm_bio_prison_cell *cell)
{
    int r;
    dm_block_t data_block;

    /*
     * Remap empty bios (flushes) immediately, without provisioning.
     */
    if (!bio->bi_size) {
        dm_cell_release_singleton(cell, bio);
        remap_and_issue(tc, bio, 0);
        return;
    }

    /*
     * Fill read bios with zeroes and complete them immediately.
     */
    if (bio_data_dir(bio) == READ) {
        zero_fill_bio(bio);
        dm_cell_release_singleton(cell, bio);
        bio_endio(bio, 0);
        return;
    }

    r = alloc_data_block(tc, &data_block);
    switch (r) {
    case 0:
        if (tc->origin_dev)
            schedule_external_copy(tc, block, data_block, cell, bio);
        else
            schedule_zero(tc, block, data_block, cell, bio);
        break;

    case -ENOSPC:
        no_space(cell);
        break;

    default:
        DMERR("%s: alloc_data_block() failed, error = %d", __func__, r);
        set_pool_mode(tc->pool, PM_READ_ONLY);
        dm_cell_error(cell);
        break;
    }
}

static void process_bio(struct thin_c *tc, struct bio *bio)
{
    int r;
    dm_block_t block = get_bio_block(tc, bio);
    struct dm_bio_prison_cell *cell;
    struct dm_cell_key key;
    struct dm_thin_lookup_result lookup_result;

    /*
     * If cell is already occupied, then the block is already
     * being provisioned so we have nothing further to do here.
     */
    build_virtual_key(tc->td, block, &key);
    if (dm_bio_detain(tc->pool->prison, &key, bio, &cell))
        return;

    r = dm_thin_find_block(tc->td, block, 1, &lookup_result);
    switch (r) {
    case 0:
        /*
         * We can release this cell now.  This thread is the only
         * one that puts bios into a cell, and we know there were
         * no preceding bios.
         */
        /*
         * TODO: this will probably have to change when discard goes
         * back in.
         */
        dm_cell_release_singleton(cell, bio);

        if (lookup_result.shared)
            process_shared_bio(tc, bio, block, &lookup_result);
        else
            remap_and_issue(tc, bio, lookup_result.block);
        break;

    case -ENODATA:
        if (bio_data_dir(bio) == READ && tc->origin_dev) {
            dm_cell_release_singleton(cell, bio);
            remap_to_origin_and_issue(tc, bio);
        } else
            provision_block(tc, bio, block, cell);
        break;

    default:
        DMERR("dm_thin_find_block() failed, error = %d", r);
        dm_cell_release_singleton(cell, bio);
        bio_io_error(bio);
        break;
    }
}

static void process_bio_read_only(struct thin_c *tc, struct bio *bio)
{
    int r;
    int rw = bio_data_dir(bio);
    dm_block_t block = get_bio_block(tc, bio);
    struct dm_thin_lookup_result lookup_result;

    r = dm_thin_find_block(tc->td, block, 1, &lookup_result);
    switch (r) {
    case 0:
        if (lookup_result.shared && (rw == WRITE) && bio->bi_size)
            bio_io_error(bio);
        else
            remap_and_issue(tc, bio, lookup_result.block);
        break;

    case -ENODATA:
        if (rw != READ) {
            bio_io_error(bio);
            break;
        }

        if (tc->origin_dev) {
            remap_to_origin_and_issue(tc, bio);
            break;
        }

        zero_fill_bio(bio);
        bio_endio(bio, 0);
        break;

    default:
        DMERR("dm_thin_find_block() failed, error = %d", r);
        bio_io_error(bio);
        break;
    }
}

static void process_bio_fail(struct thin_c *tc, struct bio *bio)
{
    bio_io_error(bio);
}

static int need_commit_due_to_time(struct pool *pool)
{
    return jiffies < pool->last_commit_jiffies ||
           jiffies > pool->last_commit_jiffies + COMMIT_PERIOD;
}

static void process_deferred_bios(struct pool *pool)
{
    unsigned long flags;
    struct bio *bio;
    struct bio_list bios;

    bio_list_init(&bios);

    spin_lock_irqsave(&pool->lock, flags);
    bio_list_merge(&bios, &pool->deferred_bios);
    bio_list_init(&pool->deferred_bios);
    spin_unlock_irqrestore(&pool->lock, flags);

    while ((bio = bio_list_pop(&bios))) {
        struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;
        struct thin_c *tc = h->tc;

        /*
         * If we've got no free new_mapping structs, and processing
         * this bio might require one, we pause until there are some
         * prepared mappings to process.
         */
        if (ensure_next_mapping(pool)) {
            spin_lock_irqsave(&pool->lock, flags);
            bio_list_merge(&pool->deferred_bios, &bios);
            spin_unlock_irqrestore(&pool->lock, flags);

            break;
        }

        if (bio->bi_rw & REQ_DISCARD)
            pool->process_discard(tc, bio);
        else
            pool->process_bio(tc, bio);
    }

    /*
     * If there are any deferred flush bios, we must commit
     * the metadata before issuing them.
     */
    bio_list_init(&bios);
    spin_lock_irqsave(&pool->lock, flags);
    bio_list_merge(&bios, &pool->deferred_flush_bios);
    bio_list_init(&pool->deferred_flush_bios);
    spin_unlock_irqrestore(&pool->lock, flags);

    if (bio_list_empty(&bios) && !need_commit_due_to_time(pool))
        return;

    if (commit_or_fallback(pool)) {
        while ((bio = bio_list_pop(&bios)))
            bio_io_error(bio);
        return;
    }
    pool->last_commit_jiffies = jiffies;

    while ((bio = bio_list_pop(&bios)))
        generic_make_request(bio);
}

static void do_worker(struct work_struct *ws)
{
    struct pool *pool = container_of(ws, struct pool, worker);

    process_prepared(pool, &pool->prepared_mappings, &pool->process_prepared_mapping);
    process_prepared(pool, &pool->prepared_discards, &pool->process_prepared_discard);
    process_deferred_bios(pool);
}

/*
 * We want to commit periodically so that not too much
 * unwritten data builds up.
 */
static void do_waker(struct work_struct *ws)
{
    struct pool *pool = container_of(to_delayed_work(ws), struct pool, waker);
    wake_worker(pool);
    queue_delayed_work(pool->wq, &pool->waker, COMMIT_PERIOD);
}

/*----------------------------------------------------------------*/

static enum pool_mode get_pool_mode(struct pool *pool)
{
    return pool->pf.mode;
}

static void set_pool_mode(struct pool *pool, enum pool_mode mode)
{
    int r;

    pool->pf.mode = mode;

    switch (mode) {
    case PM_FAIL:
        DMERR("switching pool to failure mode");
        pool->process_bio = process_bio_fail;
        pool->process_discard = process_bio_fail;
        pool->process_prepared_mapping = process_prepared_mapping_fail;
        pool->process_prepared_discard = process_prepared_discard_fail;
        break;

    case PM_READ_ONLY:
        DMERR("switching pool to read-only mode");
        r = dm_pool_abort_metadata(pool->pmd);
        if (r) {
            DMERR("aborting transaction failed");
            set_pool_mode(pool, PM_FAIL);
        } else {
            dm_pool_metadata_read_only(pool->pmd);
            pool->process_bio = process_bio_read_only;
            pool->process_discard = process_discard;
            pool->process_prepared_mapping = process_prepared_mapping_fail;
            pool->process_prepared_discard = process_prepared_discard_passdown;
        }
        break;

    case PM_WRITE:
        pool->process_bio = process_bio;
        pool->process_discard = process_discard;
        pool->process_prepared_mapping = process_prepared_mapping;
        pool->process_prepared_discard = process_prepared_discard;
        break;
    }
}

/*----------------------------------------------------------------*/

/*
 * Mapping functions.
 */

/*
 * Called only while mapping a thin bio to hand it over to the workqueue.
 */
static void thin_defer_bio(struct thin_c *tc, struct bio *bio)
{
    unsigned long flags;
    struct pool *pool = tc->pool;

    spin_lock_irqsave(&pool->lock, flags);
    bio_list_add(&pool->deferred_bios, bio);
    spin_unlock_irqrestore(&pool->lock, flags);

    wake_worker(pool);
}

static struct dm_thin_endio_hook *thin_hook_bio(struct thin_c *tc, struct bio *bio)
{
    struct pool *pool = tc->pool;
    struct dm_thin_endio_hook *h = mempool_alloc(pool->endio_hook_pool, GFP_NOIO);

    h->tc = tc;
    h->shared_read_entry = NULL;
    h->all_io_entry = bio->bi_rw & REQ_DISCARD ? NULL : dm_deferred_entry_inc(pool->all_io_ds);
    h->overwrite_mapping = NULL;

    return h;
}

/*
 * Non-blocking function called from the thin target's map function.
 */
static int thin_bio_map(struct dm_target *ti, struct bio *bio,
            union map_info *map_context)
{
    int r;
    struct thin_c *tc = ti->private;
    dm_block_t block = get_bio_block(tc, bio);
    struct dm_thin_device *td = tc->td;
    struct dm_thin_lookup_result result;

    map_context->ptr = thin_hook_bio(tc, bio);

    if (get_pool_mode(tc->pool) == PM_FAIL) {
        bio_io_error(bio);
        return DM_MAPIO_SUBMITTED;
    }

    if (bio->bi_rw & (REQ_DISCARD | REQ_FLUSH | REQ_FUA)) {
        thin_defer_bio(tc, bio);
        return DM_MAPIO_SUBMITTED;
    }

    r = dm_thin_find_block(td, block, 0, &result);

    /*
     * Note that we defer readahead too.
     */
    switch (r) {
    case 0:
        if (unlikely(result.shared)) {
            /*
             * We have a race condition here between the
             * result.shared value returned by the lookup and
             * snapshot creation, which may cause new
             * sharing.
             *
             * To avoid this always quiesce the origin before
             * taking the snap.  You want to do this anyway to
             * ensure a consistent application view
             * (i.e. lockfs).
             *
             * More distant ancestors are irrelevant. The
             * shared flag will be set in their case.
             */
            thin_defer_bio(tc, bio);
            r = DM_MAPIO_SUBMITTED;
        } else {
            remap(tc, bio, result.block);
            r = DM_MAPIO_REMAPPED;
        }
        break;

    case -ENODATA:
        if (get_pool_mode(tc->pool) == PM_READ_ONLY) {
            /*
             * This block isn't provisioned, and we have no way
             * of doing so.  Just error it.
             */
            bio_io_error(bio);
            r = DM_MAPIO_SUBMITTED;
            break;
        }
        /* fall through */

    case -EWOULDBLOCK:
        /*
         * In future, the failed dm_thin_find_block above could
         * provide the hint to load the metadata into cache.
         */
        thin_defer_bio(tc, bio);
        r = DM_MAPIO_SUBMITTED;
        break;

    default:
        /*
         * Must always call bio_io_error on failure.
         * dm_thin_find_block can fail with -EINVAL if the
         * pool is switched to fail-io mode.
         */
        bio_io_error(bio);
        r = DM_MAPIO_SUBMITTED;
        break;
    }

    return r;
}

static int pool_is_congested(struct dm_target_callbacks *cb, int bdi_bits)
{
    int r;
    unsigned long flags;
    struct pool_c *pt = container_of(cb, struct pool_c, callbacks);

    spin_lock_irqsave(&pt->pool->lock, flags);
    r = !bio_list_empty(&pt->pool->retry_on_resume_list);
    spin_unlock_irqrestore(&pt->pool->lock, flags);

    if (!r) {
        struct request_queue *q = bdev_get_queue(pt->data_dev->bdev);
        r = bdi_congested(&q->backing_dev_info, bdi_bits);
    }

    return r;
}

static void __requeue_bios(struct pool *pool)
{
    bio_list_merge(&pool->deferred_bios, &pool->retry_on_resume_list);
    bio_list_init(&pool->retry_on_resume_list);
}

/*----------------------------------------------------------------
 * Binding of control targets to a pool object
 *--------------------------------------------------------------*/
static bool data_dev_supports_discard(struct pool_c *pt)
{
    struct request_queue *q = bdev_get_queue(pt->data_dev->bdev);

    return q && blk_queue_discard(q);
}

/*
 * If discard_passdown was enabled verify that the data device
 * supports discards.  Disable discard_passdown if not.
 */
static void disable_passdown_if_not_supported(struct pool_c *pt)
{
    struct pool *pool = pt->pool;
    struct block_device *data_bdev = pt->data_dev->bdev;
    struct queue_limits *data_limits = &bdev_get_queue(data_bdev)->limits;
    sector_t block_size = pool->sectors_per_block << SECTOR_SHIFT;
    const char *reason = NULL;
    char buf[BDEVNAME_SIZE];

    if (!pt->adjusted_pf.discard_passdown)
        return;

    if (!data_dev_supports_discard(pt))
        reason = "discard unsupported";

    else if (data_limits->max_discard_sectors < pool->sectors_per_block)
        reason = "max discard sectors smaller than a block";

    else if (data_limits->discard_granularity > block_size)
        reason = "discard granularity larger than a block";

    else if (block_size & (data_limits->discard_granularity - 1))
        reason = "discard granularity not a factor of block size";

    if (reason) {
        DMWARN("Data device (%s) %s: Disabling discard passdown.", bdevname(data_bdev, buf), reason);
        pt->adjusted_pf.discard_passdown = false;
    }
}

static int bind_control_target(struct pool *pool, struct dm_target *ti)
{
    struct pool_c *pt = ti->private;

    /*
     * We want to make sure that degraded pools are never upgraded.
     */
    enum pool_mode old_mode = pool->pf.mode;
    enum pool_mode new_mode = pt->adjusted_pf.mode;

    if (old_mode > new_mode)
        new_mode = old_mode;

    pool->ti = ti;
    pool->low_water_blocks = pt->low_water_blocks;
    pool->pf = pt->adjusted_pf;

    set_pool_mode(pool, new_mode);

    return 0;
}

static void unbind_control_target(struct pool *pool, struct dm_target *ti)
{
    if (pool->ti == ti)
        pool->ti = NULL;
}

/*----------------------------------------------------------------
 * Pool creation
 *--------------------------------------------------------------*/
/* Initialize pool features. */
static void pool_features_init(struct pool_features *pf)
{
    pf->mode = PM_WRITE;
    pf->zero_new_blocks = true;
    pf->discard_enabled = true;
    pf->discard_passdown = true;
}

static void __pool_destroy(struct pool *pool)
{
    __pool_table_remove(pool);

    if (dm_pool_metadata_close(pool->pmd) < 0)
        DMWARN("%s: dm_pool_metadata_close() failed.", __func__);

    dm_bio_prison_destroy(pool->prison);
    dm_kcopyd_client_destroy(pool->copier);

    if (pool->wq)
        destroy_workqueue(pool->wq);

    if (pool->next_mapping)
        mempool_free(pool->next_mapping, pool->mapping_pool);
    mempool_destroy(pool->mapping_pool);
    mempool_destroy(pool->endio_hook_pool);
    dm_deferred_set_destroy(pool->shared_read_ds);
    dm_deferred_set_destroy(pool->all_io_ds);
    kfree(pool);
}

static struct kmem_cache *_new_mapping_cache;
static struct kmem_cache *_endio_hook_cache;

static struct pool *pool_create(struct mapped_device *pool_md,
                struct block_device *metadata_dev,
                unsigned long block_size,
                int read_only, char **error)
{
    int r;
    void *err_p;
    struct pool *pool;
    struct dm_pool_metadata *pmd;
    bool format_device = read_only ? false : true;

    pmd = dm_pool_metadata_open(metadata_dev, block_size, format_device);
    if (IS_ERR(pmd)) {
        *error = "Error creating metadata object";
        return (struct pool *)pmd;
    }

    pool = kmalloc(sizeof(*pool), GFP_KERNEL);
    if (!pool) {
        *error = "Error allocating memory for pool";
        err_p = ERR_PTR(-ENOMEM);
        goto bad_pool;
    }

    pool->pmd = pmd;
    pool->sectors_per_block = block_size;
    if (block_size & (block_size - 1))
        pool->sectors_per_block_shift = -1;
    else
        pool->sectors_per_block_shift = __ffs(block_size);
    pool->low_water_blocks = 0;
    pool_features_init(&pool->pf);
    pool->prison = dm_bio_prison_create(PRISON_CELLS);
    if (!pool->prison) {
        *error = "Error creating pool's bio prison";
        err_p = ERR_PTR(-ENOMEM);
        goto bad_prison;
    }

    pool->copier = dm_kcopyd_client_create();
    if (IS_ERR(pool->copier)) {
        r = PTR_ERR(pool->copier);
        *error = "Error creating pool's kcopyd client";
        err_p = ERR_PTR(r);
        goto bad_kcopyd_client;
    }

    /*
     * Create singlethreaded workqueue that will service all devices
     * that use this metadata.
     */
    pool->wq = alloc_ordered_workqueue("dm-" DM_MSG_PREFIX, WQ_MEM_RECLAIM);
    if (!pool->wq) {
        *error = "Error creating pool's workqueue";
        err_p = ERR_PTR(-ENOMEM);
        goto bad_wq;
    }

    INIT_WORK(&pool->worker, do_worker);
    INIT_DELAYED_WORK(&pool->waker, do_waker);
    spin_lock_init(&pool->lock);
    bio_list_init(&pool->deferred_bios);
    bio_list_init(&pool->deferred_flush_bios);
    INIT_LIST_HEAD(&pool->prepared_mappings);
    INIT_LIST_HEAD(&pool->prepared_discards);
    pool->low_water_triggered = 0;
    pool->no_free_space = 0;
    bio_list_init(&pool->retry_on_resume_list);

    pool->shared_read_ds = dm_deferred_set_create();
    if (!pool->shared_read_ds) {
        *error = "Error creating pool's shared read deferred set";
        err_p = ERR_PTR(-ENOMEM);
        goto bad_shared_read_ds;
    }

    pool->all_io_ds = dm_deferred_set_create();
    if (!pool->all_io_ds) {
        *error = "Error creating pool's all io deferred set";
        err_p = ERR_PTR(-ENOMEM);
        goto bad_all_io_ds;
    }

    pool->next_mapping = NULL;
    pool->mapping_pool = mempool_create_slab_pool(MAPPING_POOL_SIZE,
                              _new_mapping_cache);
    if (!pool->mapping_pool) {
        *error = "Error creating pool's mapping mempool";
        err_p = ERR_PTR(-ENOMEM);
        goto bad_mapping_pool;
    }

    pool->endio_hook_pool = mempool_create_slab_pool(ENDIO_HOOK_POOL_SIZE,
                             _endio_hook_cache);
    if (!pool->endio_hook_pool) {
        *error = "Error creating pool's endio_hook mempool";
        err_p = ERR_PTR(-ENOMEM);
        goto bad_endio_hook_pool;
    }
    pool->ref_count = 1;
    pool->last_commit_jiffies = jiffies;
    pool->pool_md = pool_md;
    pool->md_dev = metadata_dev;
    __pool_table_insert(pool);

    return pool;

bad_endio_hook_pool:
    mempool_destroy(pool->mapping_pool);
bad_mapping_pool:
    dm_deferred_set_destroy(pool->all_io_ds);
bad_all_io_ds:
    dm_deferred_set_destroy(pool->shared_read_ds);
bad_shared_read_ds:
    destroy_workqueue(pool->wq);
bad_wq:
    dm_kcopyd_client_destroy(pool->copier);
bad_kcopyd_client:
    dm_bio_prison_destroy(pool->prison);
bad_prison:
    kfree(pool);
bad_pool:
    if (dm_pool_metadata_close(pmd))
        DMWARN("%s: dm_pool_metadata_close() failed.", __func__);

    return err_p;
}

static void __pool_inc(struct pool *pool)
{
    BUG_ON(!mutex_is_locked(&dm_thin_pool_table.mutex));
    pool->ref_count++;
}

static void __pool_dec(struct pool *pool)
{
    BUG_ON(!mutex_is_locked(&dm_thin_pool_table.mutex));
    BUG_ON(!pool->ref_count);
    if (!--pool->ref_count)
        __pool_destroy(pool);
}

static struct pool *__pool_find(struct mapped_device *pool_md,
                struct block_device *metadata_dev,
                unsigned long block_size, int read_only,
                char **error, int *created)
{
    struct pool *pool = __pool_table_lookup_metadata_dev(metadata_dev);

    if (pool) {
        if (pool->pool_md != pool_md) {
            *error = "metadata device already in use by a pool";
            return ERR_PTR(-EBUSY);
        }
        __pool_inc(pool);

    } else {
        pool = __pool_table_lookup(pool_md);
        if (pool) {
            if (pool->md_dev != metadata_dev) {
                *error = "different pool cannot replace a pool";
                return ERR_PTR(-EINVAL);
            }
            __pool_inc(pool);

        } else {
            pool = pool_create(pool_md, metadata_dev, block_size, read_only, error);
            *created = 1;
        }
    }

    return pool;
}

/*----------------------------------------------------------------
 * Pool target methods
 *--------------------------------------------------------------*/
static void pool_dtr(struct dm_target *ti)
{
    struct pool_c *pt = ti->private;

    mutex_lock(&dm_thin_pool_table.mutex);

    unbind_control_target(pt->pool, ti);
    __pool_dec(pt->pool);
    dm_put_device(ti, pt->metadata_dev);
    dm_put_device(ti, pt->data_dev);
    kfree(pt);

    mutex_unlock(&dm_thin_pool_table.mutex);
}

static int parse_pool_features(struct dm_arg_set *as, struct pool_features *pf,
                   struct dm_target *ti)
{
    int r;
    unsigned argc;
    const char *arg_name;

    static struct dm_arg _args[] = {
        {0, 3, "Invalid number of pool feature arguments"},
    };

    /*
     * No feature arguments supplied.
     */
    if (!as->argc)
        return 0;

    r = dm_read_arg_group(_args, as, &argc, &ti->error);
    if (r)
        return -EINVAL;

    while (argc && !r) {
        arg_name = dm_shift_arg(as);
        argc--;

        if (!strcasecmp(arg_name, "skip_block_zeroing"))
            pf->zero_new_blocks = false;

        else if (!strcasecmp(arg_name, "ignore_discard"))
            pf->discard_enabled = false;

        else if (!strcasecmp(arg_name, "no_discard_passdown"))
            pf->discard_passdown = false;

        else if (!strcasecmp(arg_name, "read_only"))
            pf->mode = PM_READ_ONLY;

        else {
            ti->error = "Unrecognised pool feature requested";
            r = -EINVAL;
            break;
        }
    }

    return r;
}

/*
 * thin-pool <metadata dev> <data dev>
 *       <data block size (sectors)>
 *       <low water mark (blocks)>
 *       [<#feature args> [<arg>]*]
 *
 * Optional feature arguments are:
 *       skip_block_zeroing: skips the zeroing of newly-provisioned blocks.
 *       ignore_discard: disable discard
 *       no_discard_passdown: don't pass discards down to the data device
 */
static int pool_ctr(struct dm_target *ti, unsigned argc, char **argv)
{
    int r, pool_created = 0;
    struct pool_c *pt;
    struct pool *pool;
    struct pool_features pf;
    struct dm_arg_set as;
    struct dm_dev *data_dev;
    unsigned long block_size;
    dm_block_t low_water_blocks;
    struct dm_dev *metadata_dev;
    sector_t metadata_dev_size;
    char b[BDEVNAME_SIZE];

    /*
     * FIXME Remove validation from scope of lock.
     */
    mutex_lock(&dm_thin_pool_table.mutex);

    if (argc < 4) {
        ti->error = "Invalid argument count";
        r = -EINVAL;
        goto out_unlock;
    }
    as.argc = argc;
    as.argv = argv;

    r = dm_get_device(ti, argv[0], FMODE_READ | FMODE_WRITE, &metadata_dev);
    if (r) {
        ti->error = "Error opening metadata block device";
        goto out_unlock;
    }

    metadata_dev_size = i_size_read(metadata_dev->bdev->bd_inode) >> SECTOR_SHIFT;
    if (metadata_dev_size > THIN_METADATA_MAX_SECTORS_WARNING)
        DMWARN("Metadata device %s is larger than %u sectors: excess space will not be used.",
               bdevname(metadata_dev->bdev, b), THIN_METADATA_MAX_SECTORS);

    r = dm_get_device(ti, argv[1], FMODE_READ | FMODE_WRITE, &data_dev);
    if (r) {
        ti->error = "Error getting data device";
        goto out_metadata;
    }

    if (kstrtoul(argv[2], 10, &block_size) || !block_size ||
        block_size < DATA_DEV_BLOCK_SIZE_MIN_SECTORS ||
        block_size > DATA_DEV_BLOCK_SIZE_MAX_SECTORS ||
        block_size & (DATA_DEV_BLOCK_SIZE_MIN_SECTORS - 1)) {
        ti->error = "Invalid block size";
        r = -EINVAL;
        goto out;
    }

    if (kstrtoull(argv[3], 10, (unsigned long long *)&low_water_blocks)) {
        ti->error = "Invalid low water mark";
        r = -EINVAL;
        goto out;
    }

    /*
     * Set default pool features.
     */
    pool_features_init(&pf);

    dm_consume_args(&as, 4);
    r = parse_pool_features(&as, &pf, ti);
    if (r)
        goto out;

    pt = kzalloc(sizeof(*pt), GFP_KERNEL);
    if (!pt) {
        r = -ENOMEM;
        goto out;
    }

    pool = __pool_find(dm_table_get_md(ti->table), metadata_dev->bdev,
               block_size, pf.mode == PM_READ_ONLY, &ti->error, &pool_created);
    if (IS_ERR(pool)) {
        r = PTR_ERR(pool);
        goto out_free_pt;
    }

    /*
     * 'pool_created' reflects whether this is the first table load.
     * Top level discard support is not allowed to be changed after
     * initial load.  This would require a pool reload to trigger thin
     * device changes.
     */
    if (!pool_created && pf.discard_enabled != pool->pf.discard_enabled) {
        ti->error = "Discard support cannot be disabled once enabled";
        r = -EINVAL;
        goto out_flags_changed;
    }

    pt->pool = pool;
    pt->ti = ti;
    pt->metadata_dev = metadata_dev;
    pt->data_dev = data_dev;
    pt->low_water_blocks = low_water_blocks;
    pt->adjusted_pf = pt->requested_pf = pf;
    ti->num_flush_requests = 1;

    /*
     * Only need to enable discards if the pool should pass
     * them down to the data device.  The thin device's discard
     * processing will cause mappings to be removed from the btree.
     */
    if (pf.discard_enabled && pf.discard_passdown) {
        ti->num_discard_requests = 1;

        /*
         * Setting 'discards_supported' circumvents the normal
         * stacking of discard limits (this keeps the pool and
         * thin devices' discard limits consistent).
         */
        ti->discards_supported = true;
        ti->discard_zeroes_data_unsupported = true;
    }
    ti->private = pt;

    pt->callbacks.congested_fn = pool_is_congested;
    dm_table_add_target_callbacks(ti->table, &pt->callbacks);

    mutex_unlock(&dm_thin_pool_table.mutex);

    return 0;

out_flags_changed:
    __pool_dec(pool);
out_free_pt:
    kfree(pt);
out:
    dm_put_device(ti, data_dev);
out_metadata:
    dm_put_device(ti, metadata_dev);
out_unlock:
    mutex_unlock(&dm_thin_pool_table.mutex);

    return r;
}

static int pool_map(struct dm_target *ti, struct bio *bio,
            union map_info *map_context)
{
    int r;
    struct pool_c *pt = ti->private;
    struct pool *pool = pt->pool;
    unsigned long flags;

    /*
     * As this is a singleton target, ti->begin is always zero.
     */
    spin_lock_irqsave(&pool->lock, flags);
    bio->bi_bdev = pt->data_dev->bdev;
    r = DM_MAPIO_REMAPPED;
    spin_unlock_irqrestore(&pool->lock, flags);

    return r;
}

/*
 * Retrieves the number of blocks of the data device from
 * the superblock and compares it to the actual device size,
 * thus resizing the data device in case it has grown.
 *
 * This both copes with opening preallocated data devices in the ctr
 * being followed by a resume
 * -and-
 * calling the resume method individually after userspace has
 * grown the data device in reaction to a table event.
 */
static int pool_preresume(struct dm_target *ti)
{
    int r;
    struct pool_c *pt = ti->private;
    struct pool *pool = pt->pool;
    sector_t data_size = ti->len;
    dm_block_t sb_data_size;

    /*
     * Take control of the pool object.
     */
    r = bind_control_target(pool, ti);
    if (r)
        return r;

    (void) sector_div(data_size, pool->sectors_per_block);

    r = dm_pool_get_data_dev_size(pool->pmd, &sb_data_size);
    if (r) {
        DMERR("failed to retrieve data device size");
        return r;
    }

    if (data_size < sb_data_size) {
        DMERR("pool target too small, is %llu blocks (expected %llu)",
              (unsigned long long)data_size, sb_data_size);
        return -EINVAL;

    } else if (data_size > sb_data_size) {
        r = dm_pool_resize_data_dev(pool->pmd, data_size);
        if (r) {
            DMERR("failed to resize data device");
            /* FIXME Stricter than necessary: Rollback transaction instead here */
            set_pool_mode(pool, PM_READ_ONLY);
            return r;
        }

        (void) commit_or_fallback(pool);
    }

    return 0;
}

static void pool_resume(struct dm_target *ti)
{
    struct pool_c *pt = ti->private;
    struct pool *pool = pt->pool;
    unsigned long flags;

    spin_lock_irqsave(&pool->lock, flags);
    pool->low_water_triggered = 0;
    pool->no_free_space = 0;
    __requeue_bios(pool);
    spin_unlock_irqrestore(&pool->lock, flags);

    do_waker(&pool->waker.work);
}

static void pool_postsuspend(struct dm_target *ti)
{
    struct pool_c *pt = ti->private;
    struct pool *pool = pt->pool;

    cancel_delayed_work(&pool->waker);
    flush_workqueue(pool->wq);
    (void) commit_or_fallback(pool);
}

static int check_arg_count(unsigned argc, unsigned args_required)
{
    if (argc != args_required) {
        DMWARN("Message received with %u arguments instead of %u.",
               argc, args_required);
        return -EINVAL;
    }

    return 0;
}

static int read_dev_id(char *arg, dm_thin_id *dev_id, int warning)
{
    if (!kstrtoull(arg, 10, (unsigned long long *)dev_id) &&
        *dev_id <= MAX_DEV_ID)
        return 0;

    if (warning)
        DMWARN("Message received with invalid device id: %s", arg);

    return -EINVAL;
}

static int process_create_thin_mesg(unsigned argc, char **argv, struct pool *pool)
{
    dm_thin_id dev_id;
    int r;

    r = check_arg_count(argc, 2);
    if (r)
        return r;

    r = read_dev_id(argv[1], &dev_id, 1);
    if (r)
        return r;

    r = dm_pool_create_thin(pool->pmd, dev_id);
    if (r) {
        DMWARN("Creation of new thinly-provisioned device with id %s failed.",
               argv[1]);
        return r;
    }

    return 0;
}

static int process_create_snap_mesg(unsigned argc, char **argv, struct pool *pool)
{
    dm_thin_id dev_id;
    dm_thin_id origin_dev_id;
    int r;

    r = check_arg_count(argc, 3);
    if (r)
        return r;

    r = read_dev_id(argv[1], &dev_id, 1);
    if (r)
        return r;

    r = read_dev_id(argv[2], &origin_dev_id, 1);
    if (r)
        return r;

    r = dm_pool_create_snap(pool->pmd, dev_id, origin_dev_id);
    if (r) {
        DMWARN("Creation of new snapshot %s of device %s failed.",
               argv[1], argv[2]);
        return r;
    }

    return 0;
}

static int process_delete_mesg(unsigned argc, char **argv, struct pool *pool)
{
    dm_thin_id dev_id;
    int r;

    r = check_arg_count(argc, 2);
    if (r)
        return r;

    r = read_dev_id(argv[1], &dev_id, 1);
    if (r)
        return r;

    r = dm_pool_delete_thin_device(pool->pmd, dev_id);
    if (r)
        DMWARN("Deletion of thin device %s failed.", argv[1]);

    return r;
}

static int process_set_transaction_id_mesg(unsigned argc, char **argv, struct pool *pool)
{
    dm_thin_id old_id, new_id;
    int r;

    r = check_arg_count(argc, 3);
    if (r)
        return r;

    if (kstrtoull(argv[1], 10, (unsigned long long *)&old_id)) {
        DMWARN("set_transaction_id message: Unrecognised id %s.", argv[1]);
        return -EINVAL;
    }

    if (kstrtoull(argv[2], 10, (unsigned long long *)&new_id)) {
        DMWARN("set_transaction_id message: Unrecognised new id %s.", argv[2]);
        return -EINVAL;
    }

    r = dm_pool_set_metadata_transaction_id(pool->pmd, old_id, new_id);
    if (r) {
        DMWARN("Failed to change transaction id from %s to %s.",
               argv[1], argv[2]);
        return r;
    }

    return 0;
}

static int process_reserve_metadata_snap_mesg(unsigned argc, char **argv, struct pool *pool)
{
    int r;

    r = check_arg_count(argc, 1);
    if (r)
        return r;

    (void) commit_or_fallback(pool);

    r = dm_pool_reserve_metadata_snap(pool->pmd);
    if (r)
        DMWARN("reserve_metadata_snap message failed.");

    return r;
}

static int process_release_metadata_snap_mesg(unsigned argc, char **argv, struct pool *pool)
{
    int r;

    r = check_arg_count(argc, 1);
    if (r)
        return r;

    r = dm_pool_release_metadata_snap(pool->pmd);
    if (r)
        DMWARN("release_metadata_snap message failed.");

    return r;
}

/*
 * Messages supported:
 *   create_thin    <dev_id>
 *   create_snap    <dev_id> <origin_id>
 *   delete     <dev_id>
 *   trim       <dev_id> <new_size_in_sectors>
 *   set_transaction_id <current_trans_id> <new_trans_id>
 *   reserve_metadata_snap
 *   release_metadata_snap
 */
static int pool_message(struct dm_target *ti, unsigned argc, char **argv)
{
    int r = -EINVAL;
    struct pool_c *pt = ti->private;
    struct pool *pool = pt->pool;

    if (!strcasecmp(argv[0], "create_thin"))
        r = process_create_thin_mesg(argc, argv, pool);

    else if (!strcasecmp(argv[0], "create_snap"))
        r = process_create_snap_mesg(argc, argv, pool);

    else if (!strcasecmp(argv[0], "delete"))
        r = process_delete_mesg(argc, argv, pool);

    else if (!strcasecmp(argv[0], "set_transaction_id"))
        r = process_set_transaction_id_mesg(argc, argv, pool);

    else if (!strcasecmp(argv[0], "reserve_metadata_snap"))
        r = process_reserve_metadata_snap_mesg(argc, argv, pool);

    else if (!strcasecmp(argv[0], "release_metadata_snap"))
        r = process_release_metadata_snap_mesg(argc, argv, pool);

    else
        DMWARN("Unrecognised thin pool target message received: %s", argv[0]);

    if (!r)
        (void) commit_or_fallback(pool);

    return r;
}

static void emit_flags(struct pool_features *pf, char *result,
               unsigned sz, unsigned maxlen)
{
    unsigned count = !pf->zero_new_blocks + !pf->discard_enabled +
        !pf->discard_passdown + (pf->mode == PM_READ_ONLY);
    DMEMIT("%u ", count);

    if (!pf->zero_new_blocks)
        DMEMIT("skip_block_zeroing ");

    if (!pf->discard_enabled)
        DMEMIT("ignore_discard ");

    if (!pf->discard_passdown)
        DMEMIT("no_discard_passdown ");

    if (pf->mode == PM_READ_ONLY)
        DMEMIT("read_only ");
}

/*
 * Status line is:
 *    <transaction id> <used metadata sectors>/<total metadata sectors>
 *    <used data sectors>/<total data sectors> <held metadata root>
 */
static int pool_status(struct dm_target *ti, status_type_t type,
               unsigned status_flags, char *result, unsigned maxlen)
{
    int r;
    unsigned sz = 0;
    uint64_t transaction_id;
    dm_block_t nr_free_blocks_data;
    dm_block_t nr_free_blocks_metadata;
    dm_block_t nr_blocks_data;
    dm_block_t nr_blocks_metadata;
    dm_block_t held_root;
    char buf[BDEVNAME_SIZE];
    char buf2[BDEVNAME_SIZE];
    struct pool_c *pt = ti->private;
    struct pool *pool = pt->pool;

    switch (type) {
    case STATUSTYPE_INFO:
        if (get_pool_mode(pool) == PM_FAIL) {
            DMEMIT("Fail");
            break;
        }

        /* Commit to ensure statistics aren't out-of-date */
        if (!(status_flags & DM_STATUS_NOFLUSH_FLAG) && !dm_suspended(ti))
            (void) commit_or_fallback(pool);

        r = dm_pool_get_metadata_transaction_id(pool->pmd,
                            &transaction_id);
        if (r)
            return r;

        r = dm_pool_get_free_metadata_block_count(pool->pmd,
                              &nr_free_blocks_metadata);
        if (r)
            return r;

        r = dm_pool_get_metadata_dev_size(pool->pmd, &nr_blocks_metadata);
        if (r)
            return r;

        r = dm_pool_get_free_block_count(pool->pmd,
                         &nr_free_blocks_data);
        if (r)
            return r;

        r = dm_pool_get_data_dev_size(pool->pmd, &nr_blocks_data);
        if (r)
            return r;

        r = dm_pool_get_metadata_snap(pool->pmd, &held_root);
        if (r)
            return r;

        DMEMIT("%llu %llu/%llu %llu/%llu ",
               (unsigned long long)transaction_id,
               (unsigned long long)(nr_blocks_metadata - nr_free_blocks_metadata),
               (unsigned long long)nr_blocks_metadata,
               (unsigned long long)(nr_blocks_data - nr_free_blocks_data),
               (unsigned long long)nr_blocks_data);

        if (held_root)
            DMEMIT("%llu ", held_root);
        else
            DMEMIT("- ");

        if (pool->pf.mode == PM_READ_ONLY)
            DMEMIT("ro ");
        else
            DMEMIT("rw ");

        if (pool->pf.discard_enabled && pool->pf.discard_passdown)
            DMEMIT("discard_passdown");
        else
            DMEMIT("no_discard_passdown");

        break;

    case STATUSTYPE_TABLE:
        DMEMIT("%s %s %lu %llu ",
               format_dev_t(buf, pt->metadata_dev->bdev->bd_dev),
               format_dev_t(buf2, pt->data_dev->bdev->bd_dev),
               (unsigned long)pool->sectors_per_block,
               (unsigned long long)pt->low_water_blocks);
        emit_flags(&pt->requested_pf, result, sz, maxlen);
        break;
    }

    return 0;
}

static int pool_iterate_devices(struct dm_target *ti,
                iterate_devices_callout_fn fn, void *data)
{
    struct pool_c *pt = ti->private;

    return fn(ti, pt->data_dev, 0, ti->len, data);
}

static int pool_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
              struct bio_vec *biovec, int max_size)
{
    struct pool_c *pt = ti->private;
    struct request_queue *q = bdev_get_queue(pt->data_dev->bdev);

    if (!q->merge_bvec_fn)
        return max_size;

    bvm->bi_bdev = pt->data_dev->bdev;

    return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
}

static bool block_size_is_power_of_two(struct pool *pool)
{
    return pool->sectors_per_block_shift >= 0;
}

static void set_discard_limits(struct pool_c *pt, struct queue_limits *limits)
{
    struct pool *pool = pt->pool;
    struct queue_limits *data_limits;

    limits->max_discard_sectors = pool->sectors_per_block;

    /*
     * discard_granularity is just a hint, and not enforced.
     */
    if (pt->adjusted_pf.discard_passdown) {
        data_limits = &bdev_get_queue(pt->data_dev->bdev)->limits;
        limits->discard_granularity = data_limits->discard_granularity;
    } else if (block_size_is_power_of_two(pool))
        limits->discard_granularity = pool->sectors_per_block << SECTOR_SHIFT;
    else
        /*
         * Use largest power of 2 that is a factor of sectors_per_block
         * but at least DATA_DEV_BLOCK_SIZE_MIN_SECTORS.
         */
        limits->discard_granularity = max(1 << (ffs(pool->sectors_per_block) - 1),
                          DATA_DEV_BLOCK_SIZE_MIN_SECTORS) << SECTOR_SHIFT;
}

static void pool_io_hints(struct dm_target *ti, struct queue_limits *limits)
{
    struct pool_c *pt = ti->private;
    struct pool *pool = pt->pool;

    blk_limits_io_min(limits, 0);
    blk_limits_io_opt(limits, pool->sectors_per_block << SECTOR_SHIFT);

    /*
     * pt->adjusted_pf is a staging area for the actual features to use.
     * They get transferred to the live pool in bind_control_target()
     * called from pool_preresume().
     */
    if (!pt->adjusted_pf.discard_enabled)
        return;

    disable_passdown_if_not_supported(pt);

    set_discard_limits(pt, limits);
}

static struct target_type pool_target = {
    .name = "thin-pool",
    .features = DM_TARGET_SINGLETON | DM_TARGET_ALWAYS_WRITEABLE |
            DM_TARGET_IMMUTABLE,
    .version = {1, 5, 0},
    .module = THIS_MODULE,
    .ctr = pool_ctr,
    .dtr = pool_dtr,
    .map = pool_map,
    .postsuspend = pool_postsuspend,
    .preresume = pool_preresume,
    .resume = pool_resume,
    .message = pool_message,
    .status = pool_status,
    .merge = pool_merge,
    .iterate_devices = pool_iterate_devices,
    .io_hints = pool_io_hints,
};

/*----------------------------------------------------------------
 * Thin target methods
 *--------------------------------------------------------------*/
static void thin_dtr(struct dm_target *ti)
{
    struct thin_c *tc = ti->private;

    mutex_lock(&dm_thin_pool_table.mutex);

    __pool_dec(tc->pool);
    dm_pool_close_thin_device(tc->td);
    dm_put_device(ti, tc->pool_dev);
    if (tc->origin_dev)
        dm_put_device(ti, tc->origin_dev);
    kfree(tc);

    mutex_unlock(&dm_thin_pool_table.mutex);
}

/*
 * Thin target parameters:
 *
 * <pool_dev> <dev_id> [origin_dev]
 *
 * pool_dev: the path to the pool (eg, /dev/mapper/my_pool)
 * dev_id: the internal device identifier
 * origin_dev: a device external to the pool that should act as the origin
 *
 * If the pool device has discards disabled, they get disabled for the thin
 * device as well.
 */
static int thin_ctr(struct dm_target *ti, unsigned argc, char **argv)
{
    int r;
    struct thin_c *tc;
    struct dm_dev *pool_dev, *origin_dev;
    struct mapped_device *pool_md;

    mutex_lock(&dm_thin_pool_table.mutex);

    if (argc != 2 && argc != 3) {
        ti->error = "Invalid argument count";
        r = -EINVAL;
        goto out_unlock;
    }

    tc = ti->private = kzalloc(sizeof(*tc), GFP_KERNEL);
    if (!tc) {
        ti->error = "Out of memory";
        r = -ENOMEM;
        goto out_unlock;
    }

    if (argc == 3) {
        r = dm_get_device(ti, argv[2], FMODE_READ, &origin_dev);
        if (r) {
            ti->error = "Error opening origin device";
            goto bad_origin_dev;
        }
        tc->origin_dev = origin_dev;
    }

    r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &pool_dev);
    if (r) {
        ti->error = "Error opening pool device";
        goto bad_pool_dev;
    }
    tc->pool_dev = pool_dev;

    if (read_dev_id(argv[1], (unsigned long long *)&tc->dev_id, 0)) {
        ti->error = "Invalid device id";
        r = -EINVAL;
        goto bad_common;
    }

    pool_md = dm_get_md(tc->pool_dev->bdev->bd_dev);
    if (!pool_md) {
        ti->error = "Couldn't get pool mapped device";
        r = -EINVAL;
        goto bad_common;
    }

    tc->pool = __pool_table_lookup(pool_md);
    if (!tc->pool) {
        ti->error = "Couldn't find pool object";
        r = -EINVAL;
        goto bad_pool_lookup;
    }
    __pool_inc(tc->pool);

    if (get_pool_mode(tc->pool) == PM_FAIL) {
        ti->error = "Couldn't open thin device, Pool is in fail mode";
        goto bad_thin_open;
    }

    r = dm_pool_open_thin_device(tc->pool->pmd, tc->dev_id, &tc->td);
    if (r) {
        ti->error = "Couldn't open thin internal device";
        goto bad_thin_open;
    }

    r = dm_set_target_max_io_len(ti, tc->pool->sectors_per_block);
    if (r)
        goto bad_thin_open;

    ti->num_flush_requests = 1;
    ti->flush_supported = true;

    /* In case the pool supports discards, pass them on. */
    if (tc->pool->pf.discard_enabled) {
        ti->discards_supported = true;
        ti->num_discard_requests = 1;
        ti->discard_zeroes_data_unsupported = true;
        /* Discard requests must be split on a block boundary */
        ti->split_discard_requests = true;
    }

    dm_put(pool_md);

    mutex_unlock(&dm_thin_pool_table.mutex);

    return 0;

bad_thin_open:
    __pool_dec(tc->pool);
bad_pool_lookup:
    dm_put(pool_md);
bad_common:
    dm_put_device(ti, tc->pool_dev);
bad_pool_dev:
    if (tc->origin_dev)
        dm_put_device(ti, tc->origin_dev);
bad_origin_dev:
    kfree(tc);
out_unlock:
    mutex_unlock(&dm_thin_pool_table.mutex);

    return r;
}

static int thin_map(struct dm_target *ti, struct bio *bio,
            union map_info *map_context)
{
    bio->bi_sector = dm_target_offset(ti, bio->bi_sector);

    return thin_bio_map(ti, bio, map_context);
}

static int thin_endio(struct dm_target *ti,
              struct bio *bio, int err,
              union map_info *map_context)
{
    unsigned long flags;
    struct dm_thin_endio_hook *h = map_context->ptr;
    struct list_head work;
    struct dm_thin_new_mapping *m, *tmp;
    struct pool *pool = h->tc->pool;

    if (h->shared_read_entry) {
        INIT_LIST_HEAD(&work);
        dm_deferred_entry_dec(h->shared_read_entry, &work);

        spin_lock_irqsave(&pool->lock, flags);
        list_for_each_entry_safe(m, tmp, &work, list) {
            list_del(&m->list);
            m->quiesced = 1;
            __maybe_add_mapping(m);
        }
        spin_unlock_irqrestore(&pool->lock, flags);
    }

    if (h->all_io_entry) {
        INIT_LIST_HEAD(&work);
        dm_deferred_entry_dec(h->all_io_entry, &work);
        spin_lock_irqsave(&pool->lock, flags);
        list_for_each_entry_safe(m, tmp, &work, list)
            list_add(&m->list, &pool->prepared_discards);
        spin_unlock_irqrestore(&pool->lock, flags);
    }

    mempool_free(h, pool->endio_hook_pool);

    return 0;
}

static void thin_postsuspend(struct dm_target *ti)
{
    if (dm_noflush_suspending(ti))
        requeue_io((struct thin_c *)ti->private);
}

/*
 * <nr mapped sectors> <highest mapped sector>
 */
static int thin_status(struct dm_target *ti, status_type_t type,
               unsigned status_flags, char *result, unsigned maxlen)
{
    int r;
    ssize_t sz = 0;
    dm_block_t mapped, highest;
    char buf[BDEVNAME_SIZE];
    struct thin_c *tc = ti->private;

    if (get_pool_mode(tc->pool) == PM_FAIL) {
        DMEMIT("Fail");
        return 0;
    }

    if (!tc->td)
        DMEMIT("-");
    else {
        switch (type) {
        case STATUSTYPE_INFO:
            r = dm_thin_get_mapped_count(tc->td, &mapped);
            if (r)
                return r;

            r = dm_thin_get_highest_mapped_block(tc->td, &highest);
            if (r < 0)
                return r;

            DMEMIT("%llu ", mapped * tc->pool->sectors_per_block);
            if (r)
                DMEMIT("%llu", ((highest + 1) *
                        tc->pool->sectors_per_block) - 1);
            else
                DMEMIT("-");
            break;

        case STATUSTYPE_TABLE:
            DMEMIT("%s %lu",
                   format_dev_t(buf, tc->pool_dev->bdev->bd_dev),
                   (unsigned long) tc->dev_id);
            if (tc->origin_dev)
                DMEMIT(" %s", format_dev_t(buf, tc->origin_dev->bdev->bd_dev));
            break;
        }
    }

    return 0;
}

static int thin_iterate_devices(struct dm_target *ti,
                iterate_devices_callout_fn fn, void *data)
{
    sector_t blocks;
    struct thin_c *tc = ti->private;
    struct pool *pool = tc->pool;

    /*
     * We can't call dm_pool_get_data_dev_size() since that blocks.  So
     * we follow a more convoluted path through to the pool's target.
     */
    if (!pool->ti)
        return 0;   /* nothing is bound */

    blocks = pool->ti->len;
    (void) sector_div(blocks, pool->sectors_per_block);
    if (blocks)
        return fn(ti, tc->pool_dev, 0, pool->sectors_per_block * blocks, data);

    return 0;
}

/*
 * A thin device always inherits its queue limits from its pool.
 */
static void thin_io_hints(struct dm_target *ti, struct queue_limits *limits)
{
    struct thin_c *tc = ti->private;

    *limits = bdev_get_queue(tc->pool_dev->bdev)->limits;
}

static struct target_type thin_target = {
    .name = "thin",
    .version = {1, 5, 0},
    .module = THIS_MODULE,
    .ctr = thin_ctr,
    .dtr = thin_dtr,
    .map = thin_map,
    .end_io = thin_endio,
    .postsuspend = thin_postsuspend,
    .status = thin_status,
    .iterate_devices = thin_iterate_devices,
    .io_hints = thin_io_hints,
};

/*----------------------------------------------------------------*/

static int __init dm_thin_init(void)
{
    int r;

    pool_table_init();

    r = dm_register_target(&thin_target);
    if (r)
        return r;

    r = dm_register_target(&pool_target);
    if (r)
        goto bad_pool_target;

    r = -ENOMEM;

    _new_mapping_cache = KMEM_CACHE(dm_thin_new_mapping, 0);
    if (!_new_mapping_cache)
        goto bad_new_mapping_cache;

    _endio_hook_cache = KMEM_CACHE(dm_thin_endio_hook, 0);
    if (!_endio_hook_cache)
        goto bad_endio_hook_cache;

    return 0;

bad_endio_hook_cache:
    kmem_cache_destroy(_new_mapping_cache);
bad_new_mapping_cache:
    dm_unregister_target(&pool_target);
bad_pool_target:
    dm_unregister_target(&thin_target);

    return r;
}

static void dm_thin_exit(void)
{
    dm_unregister_target(&thin_target);
    dm_unregister_target(&pool_target);

    kmem_cache_destroy(_new_mapping_cache);
    kmem_cache_destroy(_endio_hook_cache);
}

module_init(dm_thin_init);
module_exit(dm_thin_exit);

MODULE_DESCRIPTION(DM_NAME " thin provisioning target");
MODULE_AUTHOR("Joe Thornber <[email protected]>");
MODULE_LICENSE("GPL");