dm: send just one event on resize, not two

[thirdparty/kernel/linux.git] / drivers / md / dm.c

/*
 * Copyright (C) 2001, 2002 Sistina Software (UK) Limited.
 * Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.
 *
 * This file is released under the GPL.
 */

#include "dm-core.h"
#include "dm-rq.h"
#include "dm-uevent.h"
#include "dm-ima.h"

#include <linux/init.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/sched/mm.h>
#include <linux/sched/signal.h>
#include <linux/blkpg.h>
#include <linux/bio.h>
#include <linux/mempool.h>
#include <linux/dax.h>
#include <linux/slab.h>
#include <linux/idr.h>
#include <linux/uio.h>
#include <linux/hdreg.h>
#include <linux/delay.h>
#include <linux/wait.h>
#include <linux/pr.h>
#include <linux/refcount.h>
#include <linux/part_stat.h>
#include <linux/blk-crypto.h>
#include <linux/blk-crypto-profile.h>

#define DM_MSG_PREFIX "core"

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

/*
 * For REQ_POLLED fs bio, this flag is set if we link mapped underlying
 * dm_io into one list, and reuse bio->bi_private as the list head. Before
 * ending this fs bio, we will recover its ->bi_private.
 */
#define REQ_DM_POLL_LIST        REQ_DRV

static const char *_name = DM_NAME;

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

static DEFINE_IDR(_minor_idr);

static DEFINE_SPINLOCK(_minor_lock);

static void do_deferred_remove(struct work_struct *w);

static DECLARE_WORK(deferred_remove_work, do_deferred_remove);

static struct workqueue_struct *deferred_remove_workqueue;

atomic_t dm_global_event_nr = ATOMIC_INIT(0);
DECLARE_WAIT_QUEUE_HEAD(dm_global_eventq);

void dm_issue_global_event(void)
{
        atomic_inc(&dm_global_event_nr);
        wake_up(&dm_global_eventq);
}

DEFINE_STATIC_KEY_FALSE(stats_enabled);
DEFINE_STATIC_KEY_FALSE(swap_bios_enabled);
DEFINE_STATIC_KEY_FALSE(zoned_enabled);

/*
 * One of these is allocated (on-stack) per original bio.
 */
struct clone_info {
        struct dm_table *map;
        struct bio *bio;
        struct dm_io *io;
        sector_t sector;
        unsigned sector_count;
        bool is_abnormal_io:1;
        bool submit_as_polled:1;
};

static inline struct dm_target_io *clone_to_tio(struct bio *clone)
{
        return container_of(clone, struct dm_target_io, clone);
}

void *dm_per_bio_data(struct bio *bio, size_t data_size)
{
        if (!dm_tio_flagged(clone_to_tio(bio), DM_TIO_INSIDE_DM_IO))
                return (char *)bio - DM_TARGET_IO_BIO_OFFSET - data_size;
        return (char *)bio - DM_IO_BIO_OFFSET - data_size;
}
EXPORT_SYMBOL_GPL(dm_per_bio_data);

struct bio *dm_bio_from_per_bio_data(void *data, size_t data_size)
{
        struct dm_io *io = (struct dm_io *)((char *)data + data_size);
        if (io->magic == DM_IO_MAGIC)
                return (struct bio *)((char *)io + DM_IO_BIO_OFFSET);
        BUG_ON(io->magic != DM_TIO_MAGIC);
        return (struct bio *)((char *)io + DM_TARGET_IO_BIO_OFFSET);
}
EXPORT_SYMBOL_GPL(dm_bio_from_per_bio_data);

unsigned dm_bio_get_target_bio_nr(const struct bio *bio)
{
        return container_of(bio, struct dm_target_io, clone)->target_bio_nr;
}
EXPORT_SYMBOL_GPL(dm_bio_get_target_bio_nr);

#define MINOR_ALLOCED ((void *)-1)

#define DM_NUMA_NODE NUMA_NO_NODE
static int dm_numa_node = DM_NUMA_NODE;

#define DEFAULT_SWAP_BIOS       (8 * 1048576 / PAGE_SIZE)
static int swap_bios = DEFAULT_SWAP_BIOS;
static int get_swap_bios(void)
{
        int latch = READ_ONCE(swap_bios);
        if (unlikely(latch <= 0))
                latch = DEFAULT_SWAP_BIOS;
        return latch;
}

struct table_device {
        struct list_head list;
        refcount_t count;
        struct dm_dev dm_dev;
};

/*
 * Bio-based DM's mempools' reserved IOs set by the user.
 */
#define RESERVED_BIO_BASED_IOS          16
static unsigned reserved_bio_based_ios = RESERVED_BIO_BASED_IOS;

static int __dm_get_module_param_int(int *module_param, int min, int max)
{
        int param = READ_ONCE(*module_param);
        int modified_param = 0;
        bool modified = true;

        if (param < min)
                modified_param = min;
        else if (param > max)
                modified_param = max;
        else
                modified = false;

        if (modified) {
                (void)cmpxchg(module_param, param, modified_param);
                param = modified_param;
        }

        return param;
}

unsigned __dm_get_module_param(unsigned *module_param,
                               unsigned def, unsigned max)
{
        unsigned param = READ_ONCE(*module_param);
        unsigned modified_param = 0;

        if (!param)
                modified_param = def;
        else if (param > max)
                modified_param = max;

        if (modified_param) {
                (void)cmpxchg(module_param, param, modified_param);
                param = modified_param;
        }

        return param;
}

unsigned dm_get_reserved_bio_based_ios(void)
{
        return __dm_get_module_param(&reserved_bio_based_ios,
                                     RESERVED_BIO_BASED_IOS, DM_RESERVED_MAX_IOS);
}
EXPORT_SYMBOL_GPL(dm_get_reserved_bio_based_ios);

static unsigned dm_get_numa_node(void)
{
        return __dm_get_module_param_int(&dm_numa_node,
                                         DM_NUMA_NODE, num_online_nodes() - 1);
}

static int __init local_init(void)
{
        int r;

        r = dm_uevent_init();
        if (r)
                return r;

        deferred_remove_workqueue = alloc_workqueue("kdmremove", WQ_UNBOUND, 1);
        if (!deferred_remove_workqueue) {
                r = -ENOMEM;
                goto out_uevent_exit;
        }

        _major = major;
        r = register_blkdev(_major, _name);
        if (r < 0)
                goto out_free_workqueue;

        if (!_major)
                _major = r;

        return 0;

out_free_workqueue:
        destroy_workqueue(deferred_remove_workqueue);
out_uevent_exit:
        dm_uevent_exit();

        return r;
}

static void local_exit(void)
{
        flush_scheduled_work();
        destroy_workqueue(deferred_remove_workqueue);

        unregister_blkdev(_major, _name);
        dm_uevent_exit();

        _major = 0;

        DMINFO("cleaned up");
}

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

static void (*_exits[])(void) = {
        local_exit,
        dm_target_exit,
        dm_linear_exit,
        dm_stripe_exit,
        dm_io_exit,
        dm_kcopyd_exit,
        dm_interface_exit,
        dm_statistics_exit,
};

static int __init dm_init(void)
{
        const int count = ARRAY_SIZE(_inits);
        int r, i;

#if (IS_ENABLED(CONFIG_IMA) && !IS_ENABLED(CONFIG_IMA_DISABLE_HTABLE))
        DMWARN("CONFIG_IMA_DISABLE_HTABLE is disabled."
               " Duplicate IMA measurements will not be recorded in the IMA log.");
#endif

        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]();

        /*
         * Should be empty by this point.
         */
        idr_destroy(&_minor_idr);
}

/*
 * Block device functions
 */
int dm_deleting_md(struct mapped_device *md)
{
        return test_bit(DMF_DELETING, &md->flags);
}

static int dm_blk_open(struct block_device *bdev, fmode_t mode)
{
        struct mapped_device *md;

        spin_lock(&_minor_lock);

        md = bdev->bd_disk->private_data;
        if (!md)
                goto out;

        if (test_bit(DMF_FREEING, &md->flags) ||
            dm_deleting_md(md)) {
                md = NULL;
                goto out;
        }

        dm_get(md);
        atomic_inc(&md->open_count);
out:
        spin_unlock(&_minor_lock);

        return md ? 0 : -ENXIO;
}

static void dm_blk_close(struct gendisk *disk, fmode_t mode)
{
        struct mapped_device *md;

        spin_lock(&_minor_lock);

        md = disk->private_data;
        if (WARN_ON(!md))
                goto out;

        if (atomic_dec_and_test(&md->open_count) &&
            (test_bit(DMF_DEFERRED_REMOVE, &md->flags)))
                queue_work(deferred_remove_workqueue, &deferred_remove_work);

        dm_put(md);
out:
        spin_unlock(&_minor_lock);
}

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, bool mark_deferred, bool only_deferred)
{
        int r = 0;

        spin_lock(&_minor_lock);

        if (dm_open_count(md)) {
                r = -EBUSY;
                if (mark_deferred)
                        set_bit(DMF_DEFERRED_REMOVE, &md->flags);
        } else if (only_deferred && !test_bit(DMF_DEFERRED_REMOVE, &md->flags))
                r = -EEXIST;
        else
                set_bit(DMF_DELETING, &md->flags);

        spin_unlock(&_minor_lock);

        return r;
}

int dm_cancel_deferred_remove(struct mapped_device *md)
{
        int r = 0;

        spin_lock(&_minor_lock);

        if (test_bit(DMF_DELETING, &md->flags))
                r = -EBUSY;
        else
                clear_bit(DMF_DEFERRED_REMOVE, &md->flags);

        spin_unlock(&_minor_lock);

        return r;
}

static void do_deferred_remove(struct work_struct *w)
{
        dm_deferred_remove();
}

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_prepare_ioctl(struct mapped_device *md, int *srcu_idx,
                            struct block_device **bdev)
{
        struct dm_target *ti;
        struct dm_table *map;
        int r;

retry:
        r = -ENOTTY;
        map = dm_get_live_table(md, srcu_idx);
        if (!map || !dm_table_get_size(map))
                return r;

        /* We only support devices that have a single target */
        if (map->num_targets != 1)
                return r;

        ti = dm_table_get_target(map, 0);
        if (!ti->type->prepare_ioctl)
                return r;

        if (dm_suspended_md(md))
                return -EAGAIN;

        r = ti->type->prepare_ioctl(ti, bdev);
        if (r == -ENOTCONN && !fatal_signal_pending(current)) {
                dm_put_live_table(md, *srcu_idx);
                msleep(10);
                goto retry;
        }

        return r;
}

static void dm_unprepare_ioctl(struct mapped_device *md, int srcu_idx)
{
        dm_put_live_table(md, srcu_idx);
}

static int dm_blk_ioctl(struct block_device *bdev, fmode_t mode,
                        unsigned int cmd, unsigned long arg)
{
        struct mapped_device *md = bdev->bd_disk->private_data;
        int r, srcu_idx;

        r = dm_prepare_ioctl(md, &srcu_idx, &bdev);
        if (r < 0)
                goto out;

        if (r > 0) {
                /*
                 * Target determined this ioctl is being issued against a
                 * subset of the parent bdev; require extra privileges.
                 */
                if (!capable(CAP_SYS_RAWIO)) {
                        DMDEBUG_LIMIT(
        "%s: sending ioctl %x to DM device without required privilege.",
                                current->comm, cmd);
                        r = -ENOIOCTLCMD;
                        goto out;
                }
        }

        if (!bdev->bd_disk->fops->ioctl)
                r = -ENOTTY;
        else
                r = bdev->bd_disk->fops->ioctl(bdev, mode, cmd, arg);
out:
        dm_unprepare_ioctl(md, srcu_idx);
        return r;
}

u64 dm_start_time_ns_from_clone(struct bio *bio)
{
        return jiffies_to_nsecs(clone_to_tio(bio)->io->start_time);
}
EXPORT_SYMBOL_GPL(dm_start_time_ns_from_clone);

static bool bio_is_flush_with_data(struct bio *bio)
{
        return ((bio->bi_opf & REQ_PREFLUSH) && bio->bi_iter.bi_size);
}

static void dm_io_acct(struct dm_io *io, bool end)
{
        struct dm_stats_aux *stats_aux = &io->stats_aux;
        unsigned long start_time = io->start_time;
        struct mapped_device *md = io->md;
        struct bio *bio = io->orig_bio;
        unsigned int sectors;

        /*
         * If REQ_PREFLUSH set, don't account payload, it will be
         * submitted (and accounted) after this flush completes.
         */
        if (bio_is_flush_with_data(bio))
                sectors = 0;
        else if (likely(!(dm_io_flagged(io, DM_IO_WAS_SPLIT))))
                sectors = bio_sectors(bio);
        else
                sectors = io->sectors;

        if (!end)
                bdev_start_io_acct(bio->bi_bdev, sectors, bio_op(bio),
                                   start_time);
        else
                bdev_end_io_acct(bio->bi_bdev, bio_op(bio), start_time);

        if (static_branch_unlikely(&stats_enabled) &&
            unlikely(dm_stats_used(&md->stats))) {
                sector_t sector;

                if (likely(!dm_io_flagged(io, DM_IO_WAS_SPLIT)))
                        sector = bio->bi_iter.bi_sector;
                else
                        sector = bio_end_sector(bio) - io->sector_offset;

                dm_stats_account_io(&md->stats, bio_data_dir(bio),
                                    sector, sectors,
                                    end, start_time, stats_aux);
        }
}

static void __dm_start_io_acct(struct dm_io *io)
{
        dm_io_acct(io, false);
}

static void dm_start_io_acct(struct dm_io *io, struct bio *clone)
{
        /*
         * Ensure IO accounting is only ever started once.
         */
        if (dm_io_flagged(io, DM_IO_ACCOUNTED))
                return;

        /* Expect no possibility for race unless DM_TIO_IS_DUPLICATE_BIO. */
        if (!clone || likely(dm_tio_is_normal(clone_to_tio(clone)))) {
                dm_io_set_flag(io, DM_IO_ACCOUNTED);
        } else {
                unsigned long flags;
                /* Can afford locking given DM_TIO_IS_DUPLICATE_BIO */
                spin_lock_irqsave(&io->lock, flags);
                if (dm_io_flagged(io, DM_IO_ACCOUNTED)) {
                        spin_unlock_irqrestore(&io->lock, flags);
                        return;
                }
                dm_io_set_flag(io, DM_IO_ACCOUNTED);
                spin_unlock_irqrestore(&io->lock, flags);
        }

        __dm_start_io_acct(io);
}

static void dm_end_io_acct(struct dm_io *io)
{
        dm_io_acct(io, true);
}

static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio)
{
        struct dm_io *io;
        struct dm_target_io *tio;
        struct bio *clone;

        clone = bio_alloc_clone(NULL, bio, GFP_NOIO, &md->mempools->io_bs);
        tio = clone_to_tio(clone);
        tio->flags = 0;
        dm_tio_set_flag(tio, DM_TIO_INSIDE_DM_IO);
        tio->io = NULL;

        io = container_of(tio, struct dm_io, tio);
        io->magic = DM_IO_MAGIC;
        io->status = BLK_STS_OK;

        /* one ref is for submission, the other is for completion */
        atomic_set(&io->io_count, 2);
        this_cpu_inc(*md->pending_io);
        io->orig_bio = bio;
        io->md = md;
        spin_lock_init(&io->lock);
        io->start_time = jiffies;
        io->flags = 0;

        if (static_branch_unlikely(&stats_enabled))
                dm_stats_record_start(&md->stats, &io->stats_aux);

        return io;
}

static void free_io(struct dm_io *io)
{
        bio_put(&io->tio.clone);
}

static struct bio *alloc_tio(struct clone_info *ci, struct dm_target *ti,
                             unsigned target_bio_nr, unsigned *len, gfp_t gfp_mask)
{
        struct mapped_device *md = ci->io->md;
        struct dm_target_io *tio;
        struct bio *clone;

        if (!ci->io->tio.io) {
                /* the dm_target_io embedded in ci->io is available */
                tio = &ci->io->tio;
                /* alloc_io() already initialized embedded clone */
                clone = &tio->clone;
        } else {
                clone = bio_alloc_clone(NULL, ci->bio, gfp_mask,
                                        &md->mempools->bs);
                if (!clone)
                        return NULL;

                /* REQ_DM_POLL_LIST shouldn't be inherited */
                clone->bi_opf &= ~REQ_DM_POLL_LIST;

                tio = clone_to_tio(clone);
                tio->flags = 0; /* also clears DM_TIO_INSIDE_DM_IO */
        }

        tio->magic = DM_TIO_MAGIC;
        tio->io = ci->io;
        tio->ti = ti;
        tio->target_bio_nr = target_bio_nr;
        tio->len_ptr = len;
        tio->old_sector = 0;

        /* Set default bdev, but target must bio_set_dev() before issuing IO */
        clone->bi_bdev = md->disk->part0;
        if (unlikely(ti->needs_bio_set_dev))
                bio_set_dev(clone, md->disk->part0);

        if (len) {
                clone->bi_iter.bi_size = to_bytes(*len);
                if (bio_integrity(clone))
                        bio_integrity_trim(clone);
        }

        return clone;
}

static void free_tio(struct bio *clone)
{
        if (dm_tio_flagged(clone_to_tio(clone), DM_TIO_INSIDE_DM_IO))
                return;
        bio_put(clone);
}

/*
 * Add the bio to the list of deferred io.
 */
static void queue_io(struct mapped_device *md, struct bio *bio)
{
        unsigned long flags;

        spin_lock_irqsave(&md->deferred_lock, flags);
        bio_list_add(&md->deferred, bio);
        spin_unlock_irqrestore(&md->deferred_lock, flags);
        queue_work(md->wq, &md->work);
}

/*
 * Everyone (including functions in this file), should use this
 * function to access the md->map field, and make sure they call
 * dm_put_live_table() when finished.
 */
struct dm_table *dm_get_live_table(struct mapped_device *md,
                                   int *srcu_idx) __acquires(md->io_barrier)
{
        *srcu_idx = srcu_read_lock(&md->io_barrier);

        return srcu_dereference(md->map, &md->io_barrier);
}

void dm_put_live_table(struct mapped_device *md,
                       int srcu_idx) __releases(md->io_barrier)
{
        srcu_read_unlock(&md->io_barrier, srcu_idx);
}

void dm_sync_table(struct mapped_device *md)
{
        synchronize_srcu(&md->io_barrier);
        synchronize_rcu_expedited();
}

/*
 * A fast alternative to dm_get_live_table/dm_put_live_table.
 * The caller must not block between these two functions.
 */
static struct dm_table *dm_get_live_table_fast(struct mapped_device *md) __acquires(RCU)
{
        rcu_read_lock();
        return rcu_dereference(md->map);
}

static void dm_put_live_table_fast(struct mapped_device *md) __releases(RCU)
{
        rcu_read_unlock();
}

static inline struct dm_table *dm_get_live_table_bio(struct mapped_device *md,
                                        int *srcu_idx, blk_opf_t bio_opf)
{
        if (bio_opf & REQ_NOWAIT)
                return dm_get_live_table_fast(md);
        else
                return dm_get_live_table(md, srcu_idx);
}

static inline void dm_put_live_table_bio(struct mapped_device *md, int srcu_idx,
                                         blk_opf_t bio_opf)
{
        if (bio_opf & REQ_NOWAIT)
                dm_put_live_table_fast(md);
        else
                dm_put_live_table(md, srcu_idx);
}

static char *_dm_claim_ptr = "I belong to device-mapper";

/*
 * Open a table device so we can use it as a map destination.
 */
static struct table_device *open_table_device(struct mapped_device *md,
                dev_t dev, fmode_t mode)
{
        struct table_device *td;
        struct block_device *bdev;
        u64 part_off;
        int r;

        td = kmalloc_node(sizeof(*td), GFP_KERNEL, md->numa_node_id);
        if (!td)
                return ERR_PTR(-ENOMEM);
        refcount_set(&td->count, 1);

        bdev = blkdev_get_by_dev(dev, mode | FMODE_EXCL, _dm_claim_ptr);
        if (IS_ERR(bdev)) {
                r = PTR_ERR(bdev);
                goto out_free_td;
        }

        /*
         * We can be called before the dm disk is added.  In that case we can't
         * register the holder relation here.  It will be done once add_disk was
         * called.
         */
        if (md->disk->slave_dir) {
                r = bd_link_disk_holder(bdev, md->disk);
                if (r)
                        goto out_blkdev_put;
        }

        td->dm_dev.mode = mode;
        td->dm_dev.bdev = bdev;
        td->dm_dev.dax_dev = fs_dax_get_by_bdev(bdev, &part_off, NULL, NULL);
        format_dev_t(td->dm_dev.name, dev);
        list_add(&td->list, &md->table_devices);
        return td;

out_blkdev_put:
        blkdev_put(bdev, mode | FMODE_EXCL);
out_free_td:
        kfree(td);
        return ERR_PTR(r);
}

/*
 * Close a table device that we've been using.
 */
static void close_table_device(struct table_device *td, struct mapped_device *md)
{
        if (md->disk->slave_dir)
                bd_unlink_disk_holder(td->dm_dev.bdev, md->disk);
        blkdev_put(td->dm_dev.bdev, td->dm_dev.mode | FMODE_EXCL);
        put_dax(td->dm_dev.dax_dev);
        list_del(&td->list);
        kfree(td);
}

static struct table_device *find_table_device(struct list_head *l, dev_t dev,
                                              fmode_t mode)
{
        struct table_device *td;

        list_for_each_entry(td, l, list)
                if (td->dm_dev.bdev->bd_dev == dev && td->dm_dev.mode == mode)
                        return td;

        return NULL;
}

int dm_get_table_device(struct mapped_device *md, dev_t dev, fmode_t mode,
                        struct dm_dev **result)
{
        struct table_device *td;

        mutex_lock(&md->table_devices_lock);
        td = find_table_device(&md->table_devices, dev, mode);
        if (!td) {
                td = open_table_device(md, dev, mode);
                if (IS_ERR(td)) {
                        mutex_unlock(&md->table_devices_lock);
                        return PTR_ERR(td);
                }
        } else {
                refcount_inc(&td->count);
        }
        mutex_unlock(&md->table_devices_lock);

        *result = &td->dm_dev;
        return 0;
}

void dm_put_table_device(struct mapped_device *md, struct dm_dev *d)
{
        struct table_device *td = container_of(d, struct table_device, dm_dev);

        mutex_lock(&md->table_devices_lock);
        if (refcount_dec_and_test(&td->count))
                close_table_device(td, md);
        mutex_unlock(&md->table_devices_lock);
}

/*
 * 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) {
                DMERR("Start sector is beyond the geometry limits.");
                return -EINVAL;
        }

        md->geometry = *geo;

        return 0;
}

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

static void dm_requeue_add_io(struct dm_io *io, bool first_stage)
{
        struct mapped_device *md = io->md;

        if (first_stage) {
                struct dm_io *next = md->requeue_list;

                md->requeue_list = io;
                io->next = next;
        } else {
                bio_list_add_head(&md->deferred, io->orig_bio);
        }
}

static void dm_kick_requeue(struct mapped_device *md, bool first_stage)
{
        if (first_stage)
                queue_work(md->wq, &md->requeue_work);
        else
                queue_work(md->wq, &md->work);
}

/*
 * Return true if the dm_io's original bio is requeued.
 * io->status is updated with error if requeue disallowed.
 */
static bool dm_handle_requeue(struct dm_io *io, bool first_stage)
{
        struct bio *bio = io->orig_bio;
        bool handle_requeue = (io->status == BLK_STS_DM_REQUEUE);
        bool handle_polled_eagain = ((io->status == BLK_STS_AGAIN) &&
                                     (bio->bi_opf & REQ_POLLED));
        struct mapped_device *md = io->md;
        bool requeued = false;

        if (handle_requeue || handle_polled_eagain) {
                unsigned long flags;

                if (bio->bi_opf & REQ_POLLED) {
                        /*
                         * Upper layer won't help us poll split bio
                         * (io->orig_bio may only reflect a subset of the
                         * pre-split original) so clear REQ_POLLED.
                         */
                        bio_clear_polled(bio);
                }

                /*
                 * Target requested pushing back the I/O or
                 * polled IO hit BLK_STS_AGAIN.
                 */
                spin_lock_irqsave(&md->deferred_lock, flags);
                if ((__noflush_suspending(md) &&
                     !WARN_ON_ONCE(dm_is_zone_write(md, bio))) ||
                    handle_polled_eagain || first_stage) {
                        dm_requeue_add_io(io, first_stage);
                        requeued = true;
                } else {
                        /*
                         * noflush suspend was interrupted or this is
                         * a write to a zoned target.
                         */
                        io->status = BLK_STS_IOERR;
                }
                spin_unlock_irqrestore(&md->deferred_lock, flags);
        }

        if (requeued)
                dm_kick_requeue(md, first_stage);

        return requeued;
}

static void __dm_io_complete(struct dm_io *io, bool first_stage)
{
        struct bio *bio = io->orig_bio;
        struct mapped_device *md = io->md;
        blk_status_t io_error;
        bool requeued;

        requeued = dm_handle_requeue(io, first_stage);
        if (requeued && first_stage)
                return;

        io_error = io->status;
        if (dm_io_flagged(io, DM_IO_ACCOUNTED))
                dm_end_io_acct(io);
        else if (!io_error) {
                /*
                 * Must handle target that DM_MAPIO_SUBMITTED only to
                 * then bio_endio() rather than dm_submit_bio_remap()
                 */
                __dm_start_io_acct(io);
                dm_end_io_acct(io);
        }
        free_io(io);
        smp_wmb();
        this_cpu_dec(*md->pending_io);

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

        /* Return early if the original bio was requeued */
        if (requeued)
                return;

        if (bio_is_flush_with_data(bio)) {
                /*
                 * Preflush done for flush with data, reissue
                 * without REQ_PREFLUSH.
                 */
                bio->bi_opf &= ~REQ_PREFLUSH;
                queue_io(md, bio);
        } else {
                /* done with normal IO or empty flush */
                if (io_error)
                        bio->bi_status = io_error;
                bio_endio(bio);
        }
}

static void dm_wq_requeue_work(struct work_struct *work)
{
        struct mapped_device *md = container_of(work, struct mapped_device,
                                                requeue_work);
        unsigned long flags;
        struct dm_io *io;

        /* reuse deferred lock to simplify dm_handle_requeue */
        spin_lock_irqsave(&md->deferred_lock, flags);
        io = md->requeue_list;
        md->requeue_list = NULL;
        spin_unlock_irqrestore(&md->deferred_lock, flags);

        while (io) {
                struct dm_io *next = io->next;

                dm_io_rewind(io, &md->disk->bio_split);

                io->next = NULL;
                __dm_io_complete(io, false);
                io = next;
        }
}

/*
 * Two staged requeue:
 *
 * 1) io->orig_bio points to the real original bio, and the part mapped to
 *    this io must be requeued, instead of other parts of the original bio.
 *
 * 2) io->orig_bio points to new cloned bio which matches the requeued dm_io.
 */
static void dm_io_complete(struct dm_io *io)
{
        bool first_requeue;

        /*
         * Only dm_io that has been split needs two stage requeue, otherwise
         * we may run into long bio clone chain during suspend and OOM could
         * be triggered.
         *
         * Also flush data dm_io won't be marked as DM_IO_WAS_SPLIT, so they
         * also aren't handled via the first stage requeue.
         */
        if (dm_io_flagged(io, DM_IO_WAS_SPLIT))
                first_requeue = true;
        else
                first_requeue = false;

        __dm_io_complete(io, first_requeue);
}

/*
 * Decrements the number of outstanding ios that a bio has been
 * cloned into, completing the original io if necc.
 */
static inline void __dm_io_dec_pending(struct dm_io *io)
{
        if (atomic_dec_and_test(&io->io_count))
                dm_io_complete(io);
}

static void dm_io_set_error(struct dm_io *io, blk_status_t error)
{
        unsigned long flags;

        /* Push-back supersedes any I/O errors */
        spin_lock_irqsave(&io->lock, flags);
        if (!(io->status == BLK_STS_DM_REQUEUE &&
              __noflush_suspending(io->md))) {
                io->status = error;
        }
        spin_unlock_irqrestore(&io->lock, flags);
}

static void dm_io_dec_pending(struct dm_io *io, blk_status_t error)
{
        if (unlikely(error))
                dm_io_set_error(io, error);

        __dm_io_dec_pending(io);
}

void disable_discard(struct mapped_device *md)
{
        struct queue_limits *limits = dm_get_queue_limits(md);

        /* device doesn't really support DISCARD, disable it */
        limits->max_discard_sectors = 0;
}

void disable_write_zeroes(struct mapped_device *md)
{
        struct queue_limits *limits = dm_get_queue_limits(md);

        /* device doesn't really support WRITE ZEROES, disable it */
        limits->max_write_zeroes_sectors = 0;
}

static bool swap_bios_limit(struct dm_target *ti, struct bio *bio)
{
        return unlikely((bio->bi_opf & REQ_SWAP) != 0) && unlikely(ti->limit_swap_bios);
}

static void clone_endio(struct bio *bio)
{
        blk_status_t error = bio->bi_status;
        struct dm_target_io *tio = clone_to_tio(bio);
        struct dm_target *ti = tio->ti;
        dm_endio_fn endio = ti->type->end_io;
        struct dm_io *io = tio->io;
        struct mapped_device *md = io->md;

        if (unlikely(error == BLK_STS_TARGET)) {
                if (bio_op(bio) == REQ_OP_DISCARD &&
                    !bdev_max_discard_sectors(bio->bi_bdev))
                        disable_discard(md);
                else if (bio_op(bio) == REQ_OP_WRITE_ZEROES &&
                         !bdev_write_zeroes_sectors(bio->bi_bdev))
                        disable_write_zeroes(md);
        }

        if (static_branch_unlikely(&zoned_enabled) &&
            unlikely(bdev_is_zoned(bio->bi_bdev)))
                dm_zone_endio(io, bio);

        if (endio) {
                int r = endio(ti, bio, &error);
                switch (r) {
                case DM_ENDIO_REQUEUE:
                        if (static_branch_unlikely(&zoned_enabled)) {
                                /*
                                 * Requeuing writes to a sequential zone of a zoned
                                 * target will break the sequential write pattern:
                                 * fail such IO.
                                 */
                                if (WARN_ON_ONCE(dm_is_zone_write(md, bio)))
                                        error = BLK_STS_IOERR;
                                else
                                        error = BLK_STS_DM_REQUEUE;
                        } else
                                error = BLK_STS_DM_REQUEUE;
                        fallthrough;
                case DM_ENDIO_DONE:
                        break;
                case DM_ENDIO_INCOMPLETE:
                        /* The target will handle the io */
                        return;
                default:
                        DMCRIT("unimplemented target endio return value: %d", r);
                        BUG();
                }
        }

        if (static_branch_unlikely(&swap_bios_enabled) &&
            unlikely(swap_bios_limit(ti, bio)))
                up(&md->swap_bios_semaphore);

        free_tio(bio);
        dm_io_dec_pending(io, error);
}

/*
 * Return maximum size of I/O possible at the supplied sector up to the current
 * target boundary.
 */
static inline sector_t max_io_len_target_boundary(struct dm_target *ti,
                                                  sector_t target_offset)
{
        return ti->len - target_offset;
}

static sector_t max_io_len(struct dm_target *ti, sector_t sector)
{
        sector_t target_offset = dm_target_offset(ti, sector);
        sector_t len = max_io_len_target_boundary(ti, target_offset);

        /*
         * Does the target need to split IO even further?
         * - varied (per target) IO splitting is a tenet of DM; this
         *   explains why stacked chunk_sectors based splitting via
         *   bio_split_to_limits() isn't possible here.
         */
        if (!ti->max_io_len)
                return len;
        return min_t(sector_t, len,
                min(queue_max_sectors(ti->table->md->queue),
                    blk_chunk_sectors_left(target_offset, ti->max_io_len)));
}

int dm_set_target_max_io_len(struct dm_target *ti, sector_t len)
{
        if (len > UINT_MAX) {
                DMERR("Specified maximum size of target IO (%llu) exceeds limit (%u)",
                      (unsigned long long)len, UINT_MAX);
                ti->error = "Maximum size of target IO is too large";
                return -EINVAL;
        }

        ti->max_io_len = (uint32_t) len;

        return 0;
}
EXPORT_SYMBOL_GPL(dm_set_target_max_io_len);

static struct dm_target *dm_dax_get_live_target(struct mapped_device *md,
                                                sector_t sector, int *srcu_idx)
        __acquires(md->io_barrier)
{
        struct dm_table *map;
        struct dm_target *ti;

        map = dm_get_live_table(md, srcu_idx);
        if (!map)
                return NULL;

        ti = dm_table_find_target(map, sector);
        if (!ti)
                return NULL;

        return ti;
}

static long dm_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
                long nr_pages, enum dax_access_mode mode, void **kaddr,
                pfn_t *pfn)
{
        struct mapped_device *md = dax_get_private(dax_dev);
        sector_t sector = pgoff * PAGE_SECTORS;
        struct dm_target *ti;
        long len, ret = -EIO;
        int srcu_idx;

        ti = dm_dax_get_live_target(md, sector, &srcu_idx);

        if (!ti)
                goto out;
        if (!ti->type->direct_access)
                goto out;
        len = max_io_len(ti, sector) / PAGE_SECTORS;
        if (len < 1)
                goto out;
        nr_pages = min(len, nr_pages);
        ret = ti->type->direct_access(ti, pgoff, nr_pages, mode, kaddr, pfn);

 out:
        dm_put_live_table(md, srcu_idx);

        return ret;
}

static int dm_dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff,
                                  size_t nr_pages)
{
        struct mapped_device *md = dax_get_private(dax_dev);
        sector_t sector = pgoff * PAGE_SECTORS;
        struct dm_target *ti;
        int ret = -EIO;
        int srcu_idx;

        ti = dm_dax_get_live_target(md, sector, &srcu_idx);

        if (!ti)
                goto out;
        if (WARN_ON(!ti->type->dax_zero_page_range)) {
                /*
                 * ->zero_page_range() is mandatory dax operation. If we are
                 *  here, something is wrong.
                 */
                goto out;
        }
        ret = ti->type->dax_zero_page_range(ti, pgoff, nr_pages);
 out:
        dm_put_live_table(md, srcu_idx);

        return ret;
}

static size_t dm_dax_recovery_write(struct dax_device *dax_dev, pgoff_t pgoff,
                void *addr, size_t bytes, struct iov_iter *i)
{
        struct mapped_device *md = dax_get_private(dax_dev);
        sector_t sector = pgoff * PAGE_SECTORS;
        struct dm_target *ti;
        int srcu_idx;
        long ret = 0;

        ti = dm_dax_get_live_target(md, sector, &srcu_idx);
        if (!ti || !ti->type->dax_recovery_write)
                goto out;

        ret = ti->type->dax_recovery_write(ti, pgoff, addr, bytes, i);
out:
        dm_put_live_table(md, srcu_idx);
        return ret;
}

/*
 * A target may call dm_accept_partial_bio only from the map routine.  It is
 * allowed for all bio types except REQ_PREFLUSH, REQ_OP_ZONE_* zone management
 * operations, REQ_OP_ZONE_APPEND (zone append writes) and any bio serviced by
 * __send_duplicate_bios().
 *
 * dm_accept_partial_bio informs the dm that the target only wants to process
 * additional n_sectors sectors of the bio and the rest of the data should be
 * sent in a next bio.
 *
 * A diagram that explains the arithmetics:
 * +--------------------+---------------+-------+
 * |         1          |       2       |   3   |
 * +--------------------+---------------+-------+
 *
 * <-------------- *tio->len_ptr --------------->
 *                      <----- bio_sectors ----->
 *                      <-- n_sectors -->
 *
 * Region 1 was already iterated over with bio_advance or similar function.
 *      (it may be empty if the target doesn't use bio_advance)
 * Region 2 is the remaining bio size that the target wants to process.
 *      (it may be empty if region 1 is non-empty, although there is no reason
 *       to make it empty)
 * The target requires that region 3 is to be sent in the next bio.
 *
 * If the target wants to receive multiple copies of the bio (via num_*bios, etc),
 * the partially processed part (the sum of regions 1+2) must be the same for all
 * copies of the bio.
 */
void dm_accept_partial_bio(struct bio *bio, unsigned n_sectors)
{
        struct dm_target_io *tio = clone_to_tio(bio);
        struct dm_io *io = tio->io;
        unsigned bio_sectors = bio_sectors(bio);

        BUG_ON(dm_tio_flagged(tio, DM_TIO_IS_DUPLICATE_BIO));
        BUG_ON(op_is_zone_mgmt(bio_op(bio)));
        BUG_ON(bio_op(bio) == REQ_OP_ZONE_APPEND);
        BUG_ON(bio_sectors > *tio->len_ptr);
        BUG_ON(n_sectors > bio_sectors);

        *tio->len_ptr -= bio_sectors - n_sectors;
        bio->bi_iter.bi_size = n_sectors << SECTOR_SHIFT;

        /*
         * __split_and_process_bio() may have already saved mapped part
         * for accounting but it is being reduced so update accordingly.
         */
        dm_io_set_flag(io, DM_IO_WAS_SPLIT);
        io->sectors = n_sectors;
        io->sector_offset = bio_sectors(io->orig_bio);
}
EXPORT_SYMBOL_GPL(dm_accept_partial_bio);

/*
 * @clone: clone bio that DM core passed to target's .map function
 * @tgt_clone: clone of @clone bio that target needs submitted
 *
 * Targets should use this interface to submit bios they take
 * ownership of when returning DM_MAPIO_SUBMITTED.
 *
 * Target should also enable ti->accounts_remapped_io
 */
void dm_submit_bio_remap(struct bio *clone, struct bio *tgt_clone)
{
        struct dm_target_io *tio = clone_to_tio(clone);
        struct dm_io *io = tio->io;

        /* establish bio that will get submitted */
        if (!tgt_clone)
                tgt_clone = clone;

        /*
         * Account io->origin_bio to DM dev on behalf of target
         * that took ownership of IO with DM_MAPIO_SUBMITTED.
         */
        dm_start_io_acct(io, clone);

        trace_block_bio_remap(tgt_clone, disk_devt(io->md->disk),
                              tio->old_sector);
        submit_bio_noacct(tgt_clone);
}
EXPORT_SYMBOL_GPL(dm_submit_bio_remap);

static noinline void __set_swap_bios_limit(struct mapped_device *md, int latch)
{
        mutex_lock(&md->swap_bios_lock);
        while (latch < md->swap_bios) {
                cond_resched();
                down(&md->swap_bios_semaphore);
                md->swap_bios--;
        }
        while (latch > md->swap_bios) {
                cond_resched();
                up(&md->swap_bios_semaphore);
                md->swap_bios++;
        }
        mutex_unlock(&md->swap_bios_lock);
}

static void __map_bio(struct bio *clone)
{
        struct dm_target_io *tio = clone_to_tio(clone);
        struct dm_target *ti = tio->ti;
        struct dm_io *io = tio->io;
        struct mapped_device *md = io->md;
        int r;

        clone->bi_end_io = clone_endio;

        /*
         * Map the clone.
         */
        tio->old_sector = clone->bi_iter.bi_sector;

        if (static_branch_unlikely(&swap_bios_enabled) &&
            unlikely(swap_bios_limit(ti, clone))) {
                int latch = get_swap_bios();
                if (unlikely(latch != md->swap_bios))
                        __set_swap_bios_limit(md, latch);
                down(&md->swap_bios_semaphore);
        }

        if (static_branch_unlikely(&zoned_enabled)) {
                /*
                 * Check if the IO needs a special mapping due to zone append
                 * emulation on zoned target. In this case, dm_zone_map_bio()
                 * calls the target map operation.
                 */
                if (unlikely(dm_emulate_zone_append(md)))
                        r = dm_zone_map_bio(tio);
                else
                        r = ti->type->map(ti, clone);
        } else
                r = ti->type->map(ti, clone);

        switch (r) {
        case DM_MAPIO_SUBMITTED:
                /* target has assumed ownership of this io */
                if (!ti->accounts_remapped_io)
                        dm_start_io_acct(io, clone);
                break;
        case DM_MAPIO_REMAPPED:
                dm_submit_bio_remap(clone, NULL);
                break;
        case DM_MAPIO_KILL:
        case DM_MAPIO_REQUEUE:
                if (static_branch_unlikely(&swap_bios_enabled) &&
                    unlikely(swap_bios_limit(ti, clone)))
                        up(&md->swap_bios_semaphore);
                free_tio(clone);
                if (r == DM_MAPIO_KILL)
                        dm_io_dec_pending(io, BLK_STS_IOERR);
                else
                        dm_io_dec_pending(io, BLK_STS_DM_REQUEUE);
                break;
        default:
                DMCRIT("unimplemented target map return value: %d", r);
                BUG();
        }
}

static void setup_split_accounting(struct clone_info *ci, unsigned len)
{
        struct dm_io *io = ci->io;

        if (ci->sector_count > len) {
                /*
                 * Split needed, save the mapped part for accounting.
                 * NOTE: dm_accept_partial_bio() will update accordingly.
                 */
                dm_io_set_flag(io, DM_IO_WAS_SPLIT);
                io->sectors = len;
                io->sector_offset = bio_sectors(ci->bio);
        }
}

static void alloc_multiple_bios(struct bio_list *blist, struct clone_info *ci,
                                struct dm_target *ti, unsigned num_bios)
{
        struct bio *bio;
        int try;

        for (try = 0; try < 2; try++) {
                int bio_nr;

                if (try)
                        mutex_lock(&ci->io->md->table_devices_lock);
                for (bio_nr = 0; bio_nr < num_bios; bio_nr++) {
                        bio = alloc_tio(ci, ti, bio_nr, NULL,
                                        try ? GFP_NOIO : GFP_NOWAIT);
                        if (!bio)
                                break;

                        bio_list_add(blist, bio);
                }
                if (try)
                        mutex_unlock(&ci->io->md->table_devices_lock);
                if (bio_nr == num_bios)
                        return;

                while ((bio = bio_list_pop(blist)))
                        free_tio(bio);
        }
}

static int __send_duplicate_bios(struct clone_info *ci, struct dm_target *ti,
                                 unsigned int num_bios, unsigned *len)
{
        struct bio_list blist = BIO_EMPTY_LIST;
        struct bio *clone;
        unsigned int ret = 0;

        switch (num_bios) {
        case 0:
                break;
        case 1:
                if (len)
                        setup_split_accounting(ci, *len);
                clone = alloc_tio(ci, ti, 0, len, GFP_NOIO);
                __map_bio(clone);
                ret = 1;
                break;
        default:
                /* dm_accept_partial_bio() is not supported with shared tio->len_ptr */
                alloc_multiple_bios(&blist, ci, ti, num_bios);
                while ((clone = bio_list_pop(&blist))) {
                        dm_tio_set_flag(clone_to_tio(clone), DM_TIO_IS_DUPLICATE_BIO);
                        __map_bio(clone);
                        ret += 1;
                }
                break;
        }

        return ret;
}

static void __send_empty_flush(struct clone_info *ci)
{
        struct dm_table *t = ci->map;
        struct bio flush_bio;

        /*
         * Use an on-stack bio for this, it's safe since we don't
         * need to reference it after submit. It's just used as
         * the basis for the clone(s).
         */
        bio_init(&flush_bio, ci->io->md->disk->part0, NULL, 0,
                 REQ_OP_WRITE | REQ_PREFLUSH | REQ_SYNC);

        ci->bio = &flush_bio;
        ci->sector_count = 0;
        ci->io->tio.clone.bi_iter.bi_size = 0;

        for (unsigned int i = 0; i < t->num_targets; i++) {
                unsigned int bios;
                struct dm_target *ti = dm_table_get_target(t, i);

                atomic_add(ti->num_flush_bios, &ci->io->io_count);
                bios = __send_duplicate_bios(ci, ti, ti->num_flush_bios, NULL);
                atomic_sub(ti->num_flush_bios - bios, &ci->io->io_count);
        }

        /*
         * alloc_io() takes one extra reference for submission, so the
         * reference won't reach 0 without the following subtraction
         */
        atomic_sub(1, &ci->io->io_count);

        bio_uninit(ci->bio);
}

static void __send_changing_extent_only(struct clone_info *ci, struct dm_target *ti,
                                        unsigned num_bios)
{
        unsigned len;
        unsigned int bios;

        len = min_t(sector_t, ci->sector_count,
                    max_io_len_target_boundary(ti, dm_target_offset(ti, ci->sector)));

        atomic_add(num_bios, &ci->io->io_count);
        bios = __send_duplicate_bios(ci, ti, num_bios, &len);
        /*
         * alloc_io() takes one extra reference for submission, so the
         * reference won't reach 0 without the following (+1) subtraction
         */
        atomic_sub(num_bios - bios + 1, &ci->io->io_count);

        ci->sector += len;
        ci->sector_count -= len;
}

static bool is_abnormal_io(struct bio *bio)
{
        enum req_op op = bio_op(bio);

        if (op != REQ_OP_READ && op != REQ_OP_WRITE && op != REQ_OP_FLUSH) {
                switch (op) {
                case REQ_OP_DISCARD:
                case REQ_OP_SECURE_ERASE:
                case REQ_OP_WRITE_ZEROES:
                        return true;
                default:
                        break;
                }
        }

        return false;
}

static blk_status_t __process_abnormal_io(struct clone_info *ci,
                                          struct dm_target *ti)
{
        unsigned num_bios = 0;

        switch (bio_op(ci->bio)) {
        case REQ_OP_DISCARD:
                num_bios = ti->num_discard_bios;
                break;
        case REQ_OP_SECURE_ERASE:
                num_bios = ti->num_secure_erase_bios;
                break;
        case REQ_OP_WRITE_ZEROES:
                num_bios = ti->num_write_zeroes_bios;
                break;
        default:
                break;
        }

        /*
         * Even though the device advertised support for this type of
         * request, that does not mean every target supports it, and
         * reconfiguration might also have changed that since the
         * check was performed.
         */
        if (unlikely(!num_bios))
                return BLK_STS_NOTSUPP;

        __send_changing_extent_only(ci, ti, num_bios);
        return BLK_STS_OK;
}

/*
 * Reuse ->bi_private as dm_io list head for storing all dm_io instances
 * associated with this bio, and this bio's bi_private needs to be
 * stored in dm_io->data before the reuse.
 *
 * bio->bi_private is owned by fs or upper layer, so block layer won't
 * touch it after splitting. Meantime it won't be changed by anyone after
 * bio is submitted. So this reuse is safe.
 */
static inline struct dm_io **dm_poll_list_head(struct bio *bio)
{
        return (struct dm_io **)&bio->bi_private;
}

static void dm_queue_poll_io(struct bio *bio, struct dm_io *io)
{
        struct dm_io **head = dm_poll_list_head(bio);

        if (!(bio->bi_opf & REQ_DM_POLL_LIST)) {
                bio->bi_opf |= REQ_DM_POLL_LIST;
                /*
                 * Save .bi_private into dm_io, so that we can reuse
                 * .bi_private as dm_io list head for storing dm_io list
                 */
                io->data = bio->bi_private;

                /* tell block layer to poll for completion */
                bio->bi_cookie = ~BLK_QC_T_NONE;

                io->next = NULL;
        } else {
                /*
                 * bio recursed due to split, reuse original poll list,
                 * and save bio->bi_private too.
                 */
                io->data = (*head)->data;
                io->next = *head;
        }

        *head = io;
}

/*
 * Select the correct strategy for processing a non-flush bio.
 */
static blk_status_t __split_and_process_bio(struct clone_info *ci)
{
        struct bio *clone;
        struct dm_target *ti;
        unsigned len;

        ti = dm_table_find_target(ci->map, ci->sector);
        if (unlikely(!ti))
                return BLK_STS_IOERR;

        if (unlikely((ci->bio->bi_opf & REQ_NOWAIT) != 0) &&
            unlikely(!dm_target_supports_nowait(ti->type)))
                return BLK_STS_NOTSUPP;

        if (unlikely(ci->is_abnormal_io))
                return __process_abnormal_io(ci, ti);

        /*
         * Only support bio polling for normal IO, and the target io is
         * exactly inside the dm_io instance (verified in dm_poll_dm_io)
         */
        ci->submit_as_polled = !!(ci->bio->bi_opf & REQ_POLLED);

        len = min_t(sector_t, max_io_len(ti, ci->sector), ci->sector_count);
        setup_split_accounting(ci, len);
        clone = alloc_tio(ci, ti, 0, &len, GFP_NOIO);
        __map_bio(clone);

        ci->sector += len;
        ci->sector_count -= len;

        return BLK_STS_OK;
}

static void init_clone_info(struct clone_info *ci, struct mapped_device *md,
                            struct dm_table *map, struct bio *bio, bool is_abnormal)
{
        ci->map = map;
        ci->io = alloc_io(md, bio);
        ci->bio = bio;
        ci->is_abnormal_io = is_abnormal;
        ci->submit_as_polled = false;
        ci->sector = bio->bi_iter.bi_sector;
        ci->sector_count = bio_sectors(bio);

        /* Shouldn't happen but sector_count was being set to 0 so... */
        if (static_branch_unlikely(&zoned_enabled) &&
            WARN_ON_ONCE(op_is_zone_mgmt(bio_op(bio)) && ci->sector_count))
                ci->sector_count = 0;
}

/*
 * Entry point to split a bio into clones and submit them to the targets.
 */
static void dm_split_and_process_bio(struct mapped_device *md,
                                     struct dm_table *map, struct bio *bio)
{
        struct clone_info ci;
        struct dm_io *io;
        blk_status_t error = BLK_STS_OK;
        bool is_abnormal;

        is_abnormal = is_abnormal_io(bio);
        if (unlikely(is_abnormal)) {
                /*
                 * Use bio_split_to_limits() for abnormal IO (e.g. discard, etc)
                 * otherwise associated queue_limits won't be imposed.
                 */
                bio = bio_split_to_limits(bio);
                if (!bio)
                        return;
        }

        init_clone_info(&ci, md, map, bio, is_abnormal);
        io = ci.io;

        if (bio->bi_opf & REQ_PREFLUSH) {
                __send_empty_flush(&ci);
                /* dm_io_complete submits any data associated with flush */
                goto out;
        }

        error = __split_and_process_bio(&ci);
        if (error || !ci.sector_count)
                goto out;
        /*
         * Remainder must be passed to submit_bio_noacct() so it gets handled
         * *after* bios already submitted have been completely processed.
         */
        bio_trim(bio, io->sectors, ci.sector_count);
        trace_block_split(bio, bio->bi_iter.bi_sector);
        bio_inc_remaining(bio);
        submit_bio_noacct(bio);
out:
        /*
         * Drop the extra reference count for non-POLLED bio, and hold one
         * reference for POLLED bio, which will be released in dm_poll_bio
         *
         * Add every dm_io instance into the dm_io list head which is stored
         * in bio->bi_private, so that dm_poll_bio can poll them all.
         */
        if (error || !ci.submit_as_polled) {
                /*
                 * In case of submission failure, the extra reference for
                 * submitting io isn't consumed yet
                 */
                if (error)
                        atomic_dec(&io->io_count);
                dm_io_dec_pending(io, error);
        } else
                dm_queue_poll_io(bio, io);
}

static void dm_submit_bio(struct bio *bio)
{
        struct mapped_device *md = bio->bi_bdev->bd_disk->private_data;
        int srcu_idx;
        struct dm_table *map;
        blk_opf_t bio_opf = bio->bi_opf;

        map = dm_get_live_table_bio(md, &srcu_idx, bio_opf);

        /* If suspended, or map not yet available, queue this IO for later */
        if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)) ||
            unlikely(!map)) {
                if (bio->bi_opf & REQ_NOWAIT)
                        bio_wouldblock_error(bio);
                else if (bio->bi_opf & REQ_RAHEAD)
                        bio_io_error(bio);
                else
                        queue_io(md, bio);
                goto out;
        }

        dm_split_and_process_bio(md, map, bio);
out:
        dm_put_live_table_bio(md, srcu_idx, bio_opf);
}

static bool dm_poll_dm_io(struct dm_io *io, struct io_comp_batch *iob,
                          unsigned int flags)
{
        WARN_ON_ONCE(!dm_tio_is_normal(&io->tio));

        /* don't poll if the mapped io is done */
        if (atomic_read(&io->io_count) > 1)
                bio_poll(&io->tio.clone, iob, flags);

        /* bio_poll holds the last reference */
        return atomic_read(&io->io_count) == 1;
}

static int dm_poll_bio(struct bio *bio, struct io_comp_batch *iob,
                       unsigned int flags)
{
        struct dm_io **head = dm_poll_list_head(bio);
        struct dm_io *list = *head;
        struct dm_io *tmp = NULL;
        struct dm_io *curr, *next;

        /* Only poll normal bio which was marked as REQ_DM_POLL_LIST */
        if (!(bio->bi_opf & REQ_DM_POLL_LIST))
                return 0;

        WARN_ON_ONCE(!list);

        /*
         * Restore .bi_private before possibly completing dm_io.
         *
         * bio_poll() is only possible once @bio has been completely
         * submitted via submit_bio_noacct()'s depth-first submission.
         * So there is no dm_queue_poll_io() race associated with
         * clearing REQ_DM_POLL_LIST here.
         */
        bio->bi_opf &= ~REQ_DM_POLL_LIST;
        bio->bi_private = list->data;

        for (curr = list, next = curr->next; curr; curr = next, next =
                        curr ? curr->next : NULL) {
                if (dm_poll_dm_io(curr, iob, flags)) {
                        /*
                         * clone_endio() has already occurred, so no
                         * error handling is needed here.
                         */
                        __dm_io_dec_pending(curr);
                } else {
                        curr->next = tmp;
                        tmp = curr;
                }
        }

        /* Not done? */
        if (tmp) {
                bio->bi_opf |= REQ_DM_POLL_LIST;
                /* Reset bio->bi_private to dm_io list head */
                *head = tmp;
                return 0;
        }
        return 1;
}

/*-----------------------------------------------------------------
 * An IDR is used to keep track of allocated minor numbers.
 *---------------------------------------------------------------*/
static void free_minor(int minor)
{
        spin_lock(&_minor_lock);
        idr_remove(&_minor_idr, minor);
        spin_unlock(&_minor_lock);
}

/*
 * See if the device with a specific minor # is free.
 */
static int specific_minor(int minor)
{
        int r;

        if (minor >= (1 << MINORBITS))
                return -EINVAL;

        idr_preload(GFP_KERNEL);
        spin_lock(&_minor_lock);

        r = idr_alloc(&_minor_idr, MINOR_ALLOCED, minor, minor + 1, GFP_NOWAIT);

        spin_unlock(&_minor_lock);
        idr_preload_end();
        if (r < 0)
                return r == -ENOSPC ? -EBUSY : r;
        return 0;
}

static int next_free_minor(int *minor)
{
        int r;

        idr_preload(GFP_KERNEL);
        spin_lock(&_minor_lock);

        r = idr_alloc(&_minor_idr, MINOR_ALLOCED, 0, 1 << MINORBITS, GFP_NOWAIT);

        spin_unlock(&_minor_lock);
        idr_preload_end();
        if (r < 0)
                return r;
        *minor = r;
        return 0;
}

static const struct block_device_operations dm_blk_dops;
static const struct block_device_operations dm_rq_blk_dops;
static const struct dax_operations dm_dax_ops;

static void dm_wq_work(struct work_struct *work);

#ifdef CONFIG_BLK_INLINE_ENCRYPTION
static void dm_queue_destroy_crypto_profile(struct request_queue *q)
{
        dm_destroy_crypto_profile(q->crypto_profile);
}

#else /* CONFIG_BLK_INLINE_ENCRYPTION */

static inline void dm_queue_destroy_crypto_profile(struct request_queue *q)
{
}
#endif /* !CONFIG_BLK_INLINE_ENCRYPTION */

static void cleanup_mapped_device(struct mapped_device *md)
{
        if (md->wq)
                destroy_workqueue(md->wq);
        dm_free_md_mempools(md->mempools);

        if (md->dax_dev) {
                dax_remove_host(md->disk);
                kill_dax(md->dax_dev);
                put_dax(md->dax_dev);
                md->dax_dev = NULL;
        }

        dm_cleanup_zoned_dev(md);
        if (md->disk) {
                spin_lock(&_minor_lock);
                md->disk->private_data = NULL;
                spin_unlock(&_minor_lock);
                if (dm_get_md_type(md) != DM_TYPE_NONE) {
                        struct table_device *td;

                        dm_sysfs_exit(md);
                        list_for_each_entry(td, &md->table_devices, list) {
                                bd_unlink_disk_holder(td->dm_dev.bdev,
                                                      md->disk);
                        }

                        /*
                         * Hold lock to make sure del_gendisk() won't concurrent
                         * with open/close_table_device().
                         */
                        mutex_lock(&md->table_devices_lock);
                        del_gendisk(md->disk);
                        mutex_unlock(&md->table_devices_lock);
                }
                dm_queue_destroy_crypto_profile(md->queue);
                put_disk(md->disk);
        }

        if (md->pending_io) {
                free_percpu(md->pending_io);
                md->pending_io = NULL;
        }

        cleanup_srcu_struct(&md->io_barrier);

        mutex_destroy(&md->suspend_lock);
        mutex_destroy(&md->type_lock);
        mutex_destroy(&md->table_devices_lock);
        mutex_destroy(&md->swap_bios_lock);

        dm_mq_cleanup_mapped_device(md);
}

/*
 * Allocate and initialise a blank device with a given minor.
 */
static struct mapped_device *alloc_dev(int minor)
{
        int r, numa_node_id = dm_get_numa_node();
        struct mapped_device *md;
        void *old_md;

        md = kvzalloc_node(sizeof(*md), GFP_KERNEL, numa_node_id);
        if (!md) {
                DMERR("unable to allocate device, out of memory.");
                return NULL;
        }

        if (!try_module_get(THIS_MODULE))
                goto bad_module_get;

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

        r = init_srcu_struct(&md->io_barrier);
        if (r < 0)
                goto bad_io_barrier;

        md->numa_node_id = numa_node_id;
        md->init_tio_pdu = false;
        md->type = DM_TYPE_NONE;
        mutex_init(&md->suspend_lock);
        mutex_init(&md->type_lock);
        mutex_init(&md->table_devices_lock);
        spin_lock_init(&md->deferred_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);
        INIT_LIST_HEAD(&md->table_devices);
        spin_lock_init(&md->uevent_lock);

        /*
         * default to bio-based until DM table is loaded and md->type
         * established. If request-based table is loaded: blk-mq will
         * override accordingly.
         */
        md->disk = blk_alloc_disk(md->numa_node_id);
        if (!md->disk)
                goto bad;
        md->queue = md->disk->queue;

        init_waitqueue_head(&md->wait);
        INIT_WORK(&md->work, dm_wq_work);
        INIT_WORK(&md->requeue_work, dm_wq_requeue_work);
        init_waitqueue_head(&md->eventq);
        init_completion(&md->kobj_holder.completion);

        md->requeue_list = NULL;
        md->swap_bios = get_swap_bios();
        sema_init(&md->swap_bios_semaphore, md->swap_bios);
        mutex_init(&md->swap_bios_lock);

        md->disk->major = _major;
        md->disk->first_minor = minor;
        md->disk->minors = 1;
        md->disk->flags |= GENHD_FL_NO_PART;
        md->disk->fops = &dm_blk_dops;
        md->disk->private_data = md;
        sprintf(md->disk->disk_name, "dm-%d", minor);

        if (IS_ENABLED(CONFIG_FS_DAX)) {
                md->dax_dev = alloc_dax(md, &dm_dax_ops);
                if (IS_ERR(md->dax_dev)) {
                        md->dax_dev = NULL;
                        goto bad;
                }
                set_dax_nocache(md->dax_dev);
                set_dax_nomc(md->dax_dev);
                if (dax_add_host(md->dax_dev, md->disk))
                        goto bad;
        }

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

        md->wq = alloc_workqueue("kdmflush/%s", WQ_MEM_RECLAIM, 0, md->name);
        if (!md->wq)
                goto bad;

        md->pending_io = alloc_percpu(unsigned long);
        if (!md->pending_io)
                goto bad;

        dm_stats_init(&md->stats);

        /* Populate the mapping, nobody knows we exist yet */
        spin_lock(&_minor_lock);
        old_md = idr_replace(&_minor_idr, md, minor);
        spin_unlock(&_minor_lock);

        BUG_ON(old_md != MINOR_ALLOCED);

        return md;

bad:
        cleanup_mapped_device(md);
bad_io_barrier:
        free_minor(minor);
bad_minor:
        module_put(THIS_MODULE);
bad_module_get:
        kvfree(md);
        return NULL;
}

static void unlock_fs(struct mapped_device *md);

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

        unlock_fs(md);

        cleanup_mapped_device(md);

        WARN_ON_ONCE(!list_empty(&md->table_devices));
        dm_stats_cleanup(&md->stats);
        free_minor(minor);

        module_put(THIS_MODULE);
        kvfree(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, &disk_to_dev(md->disk)->kobj);

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

/*
 * Returns old map, which caller must destroy.
 */
static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
                               struct queue_limits *limits)
{
        struct dm_table *old_map;
        sector_t size;
        int ret;

        lockdep_assert_held(&md->suspend_lock);

        size = dm_table_get_size(t);

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

        set_capacity(md->disk, size);

        dm_table_event_callback(t, event_callback, md);

        if (dm_table_request_based(t)) {
                /*
                 * Leverage the fact that request-based DM targets are
                 * immutable singletons - used to optimize dm_mq_queue_rq.
                 */
                md->immutable_target = dm_table_get_immutable_target(t);

                /*
                 * There is no need to reload with request-based dm because the
                 * size of front_pad doesn't change.
                 *
                 * Note for future: If you are to reload bioset, prep-ed
                 * requests in the queue may refer to bio from the old bioset,
                 * so you must walk through the queue to unprep.
                 */
                if (!md->mempools) {
                        md->mempools = t->mempools;
                        t->mempools = NULL;
                }
        } else {
                /*
                 * The md may already have mempools that need changing.
                 * If so, reload bioset because front_pad may have changed
                 * because a different table was loaded.
                 */
                dm_free_md_mempools(md->mempools);
                md->mempools = t->mempools;
                t->mempools = NULL;
        }

        ret = dm_table_set_restrictions(t, md->queue, limits);
        if (ret) {
                old_map = ERR_PTR(ret);
                goto out;
        }

        old_map = rcu_dereference_protected(md->map, lockdep_is_held(&md->suspend_lock));
        rcu_assign_pointer(md->map, (void *)t);
        md->immutable_target_type = dm_table_get_immutable_target_type(t);

        if (old_map)
                dm_sync_table(md);
out:
        return old_map;
}

/*
 * Returns unbound table for the caller to free.
 */
static struct dm_table *__unbind(struct mapped_device *md)
{
        struct dm_table *map = rcu_dereference_protected(md->map, 1);

        if (!map)
                return NULL;

        dm_table_event_callback(map, NULL, NULL);
        RCU_INIT_POINTER(md->map, NULL);
        dm_sync_table(md);

        return map;
}

/*
 * Constructor for a new device.
 */
int dm_create(int minor, struct mapped_device **result)
{
        struct mapped_device *md;

        md = alloc_dev(minor);
        if (!md)
                return -ENXIO;

        dm_ima_reset_data(md);

        *result = md;
        return 0;
}

/*
 * Functions to manage md->type.
 * All are required to hold md->type_lock.
 */
void dm_lock_md_type(struct mapped_device *md)
{
        mutex_lock(&md->type_lock);
}

void dm_unlock_md_type(struct mapped_device *md)
{
        mutex_unlock(&md->type_lock);
}

void dm_set_md_type(struct mapped_device *md, enum dm_queue_mode type)
{
        BUG_ON(!mutex_is_locked(&md->type_lock));
        md->type = type;
}

enum dm_queue_mode dm_get_md_type(struct mapped_device *md)
{
        return md->type;
}

struct target_type *dm_get_immutable_target_type(struct mapped_device *md)
{
        return md->immutable_target_type;
}

/*
 * The queue_limits are only valid as long as you have a reference
 * count on 'md'.
 */
struct queue_limits *dm_get_queue_limits(struct mapped_device *md)
{
        BUG_ON(!atomic_read(&md->holders));
        return &md->queue->limits;
}
EXPORT_SYMBOL_GPL(dm_get_queue_limits);

/*
 * Setup the DM device's queue based on md's type
 */
int dm_setup_md_queue(struct mapped_device *md, struct dm_table *t)
{
        enum dm_queue_mode type = dm_table_get_type(t);
        struct queue_limits limits;
        struct table_device *td;
        int r;

        switch (type) {
        case DM_TYPE_REQUEST_BASED:
                md->disk->fops = &dm_rq_blk_dops;
                r = dm_mq_init_request_queue(md, t);
                if (r) {
                        DMERR("Cannot initialize queue for request-based dm mapped device");
                        return r;
                }
                break;
        case DM_TYPE_BIO_BASED:
        case DM_TYPE_DAX_BIO_BASED:
                break;
        case DM_TYPE_NONE:
                WARN_ON_ONCE(true);
                break;
        }

        r = dm_calculate_queue_limits(t, &limits);
        if (r) {
                DMERR("Cannot calculate initial queue limits");
                return r;
        }
        r = dm_table_set_restrictions(t, md->queue, &limits);
        if (r)
                return r;

        /*
         * Hold lock to make sure add_disk() and del_gendisk() won't concurrent
         * with open_table_device() and close_table_device().
         */
        mutex_lock(&md->table_devices_lock);
        r = add_disk(md->disk);
        mutex_unlock(&md->table_devices_lock);
        if (r)
                return r;

        /*
         * Register the holder relationship for devices added before the disk
         * was live.
         */
        list_for_each_entry(td, &md->table_devices, list) {
                r = bd_link_disk_holder(td->dm_dev.bdev, md->disk);
                if (r)
                        goto out_undo_holders;
        }

        r = dm_sysfs_init(md);
        if (r)
                goto out_undo_holders;

        md->type = type;
        return 0;

out_undo_holders:
        list_for_each_entry_continue_reverse(td, &md->table_devices, list)
                bd_unlink_disk_holder(td->dm_dev.bdev, md->disk);
        mutex_lock(&md->table_devices_lock);
        del_gendisk(md->disk);
        mutex_unlock(&md->table_devices_lock);
        return r;
}

struct mapped_device *dm_get_md(dev_t dev)
{
        struct mapped_device *md;
        unsigned minor = MINOR(dev);

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

        spin_lock(&_minor_lock);

        md = idr_find(&_minor_idr, minor);
        if (!md || md == MINOR_ALLOCED || (MINOR(disk_devt(dm_disk(md))) != minor) ||
            test_bit(DMF_FREEING, &md->flags) || dm_deleting_md(md)) {
                md = NULL;
                goto out;
        }
        dm_get(md);
out:
        spin_unlock(&_minor_lock);

        return md;
}
EXPORT_SYMBOL_GPL(dm_get_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);
        BUG_ON(test_bit(DMF_FREEING, &md->flags));
}

int dm_hold(struct mapped_device *md)
{
        spin_lock(&_minor_lock);
        if (test_bit(DMF_FREEING, &md->flags)) {
                spin_unlock(&_minor_lock);
                return -EBUSY;
        }
        dm_get(md);
        spin_unlock(&_minor_lock);
        return 0;
}
EXPORT_SYMBOL_GPL(dm_hold);

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

static void __dm_destroy(struct mapped_device *md, bool wait)
{
        struct dm_table *map;
        int srcu_idx;

        might_sleep();

        spin_lock(&_minor_lock);
        idr_replace(&_minor_idr, MINOR_ALLOCED, MINOR(disk_devt(dm_disk(md))));
        set_bit(DMF_FREEING, &md->flags);
        spin_unlock(&_minor_lock);

        blk_mark_disk_dead(md->disk);

        /*
         * Take suspend_lock so that presuspend and postsuspend methods
         * do not race with internal suspend.
         */
        mutex_lock(&md->suspend_lock);
        map = dm_get_live_table(md, &srcu_idx);
        if (!dm_suspended_md(md)) {
                dm_table_presuspend_targets(map);
                set_bit(DMF_SUSPENDED, &md->flags);
                set_bit(DMF_POST_SUSPENDING, &md->flags);
                dm_table_postsuspend_targets(map);
        }
        /* dm_put_live_table must be before msleep, otherwise deadlock is possible */
        dm_put_live_table(md, srcu_idx);
        mutex_unlock(&md->suspend_lock);

        /*
         * Rare, but there may be I/O requests still going to complete,
         * for example.  Wait for all references to disappear.
         * No one should increment the reference count of the mapped_device,
         * after the mapped_device state becomes DMF_FREEING.
         */
        if (wait)
                while (atomic_read(&md->holders))
                        msleep(1);
        else if (atomic_read(&md->holders))
                DMWARN("%s: Forcibly removing mapped_device still in use! (%d users)",
                       dm_device_name(md), atomic_read(&md->holders));

        dm_table_destroy(__unbind(md));
        free_dev(md);
}

void dm_destroy(struct mapped_device *md)
{
        __dm_destroy(md, true);
}

void dm_destroy_immediate(struct mapped_device *md)
{
        __dm_destroy(md, false);
}

void dm_put(struct mapped_device *md)
{
        atomic_dec(&md->holders);
}
EXPORT_SYMBOL_GPL(dm_put);

static bool dm_in_flight_bios(struct mapped_device *md)
{
        int cpu;
        unsigned long sum = 0;

        for_each_possible_cpu(cpu)
                sum += *per_cpu_ptr(md->pending_io, cpu);

        return sum != 0;
}

static int dm_wait_for_bios_completion(struct mapped_device *md, unsigned int task_state)
{
        int r = 0;
        DEFINE_WAIT(wait);

        while (true) {
                prepare_to_wait(&md->wait, &wait, task_state);

                if (!dm_in_flight_bios(md))
                        break;

                if (signal_pending_state(task_state, current)) {
                        r = -EINTR;
                        break;
                }

                io_schedule();
        }
        finish_wait(&md->wait, &wait);

        smp_rmb();

        return r;
}

static int dm_wait_for_completion(struct mapped_device *md, unsigned int task_state)
{
        int r = 0;

        if (!queue_is_mq(md->queue))
                return dm_wait_for_bios_completion(md, task_state);

        while (true) {
                if (!blk_mq_queue_inflight(md->queue))
                        break;

                if (signal_pending_state(task_state, current)) {
                        r = -EINTR;
                        break;
                }

                msleep(5);
        }

        return r;
}

/*
 * Process the deferred bios
 */
static void dm_wq_work(struct work_struct *work)
{
        struct mapped_device *md = container_of(work, struct mapped_device, work);
        struct bio *bio;

        while (!test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)) {
                spin_lock_irq(&md->deferred_lock);
                bio = bio_list_pop(&md->deferred);
                spin_unlock_irq(&md->deferred_lock);

                if (!bio)
                        break;

                submit_bio_noacct(bio);
        }
}

static void dm_queue_flush(struct mapped_device *md)
{
        clear_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags);
        smp_mb__after_atomic();
        queue_work(md->wq, &md->work);
}

/*
 * Swap in a new table, returning the old one for the caller to destroy.
 */
struct dm_table *dm_swap_table(struct mapped_device *md, struct dm_table *table)
{
        struct dm_table *live_map = NULL, *map = ERR_PTR(-EINVAL);
        struct queue_limits limits;
        int r;

        mutex_lock(&md->suspend_lock);

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

        /*
         * If the new table has no data devices, retain the existing limits.
         * This helps multipath with queue_if_no_path if all paths disappear,
         * then new I/O is queued based on these limits, and then some paths
         * reappear.
         */
        if (dm_table_has_no_data_devices(table)) {
                live_map = dm_get_live_table_fast(md);
                if (live_map)
                        limits = md->queue->limits;
                dm_put_live_table_fast(md);
        }

        if (!live_map) {
                r = dm_calculate_queue_limits(table, &limits);
                if (r) {
                        map = ERR_PTR(r);
                        goto out;
                }
        }

        map = __bind(md, table, &limits);
        dm_issue_global_event();

out:
        mutex_unlock(&md->suspend_lock);
        return map;
}

/*
 * Functions to lock and unlock any filesystem running on the
 * device.
 */
static int lock_fs(struct mapped_device *md)
{
        int r;

        WARN_ON(test_bit(DMF_FROZEN, &md->flags));

        r = freeze_bdev(md->disk->part0);
        if (!r)
                set_bit(DMF_FROZEN, &md->flags);
        return r;
}

static void unlock_fs(struct mapped_device *md)
{
        if (!test_bit(DMF_FROZEN, &md->flags))
                return;
        thaw_bdev(md->disk->part0);
        clear_bit(DMF_FROZEN, &md->flags);
}

/*
 * @suspend_flags: DM_SUSPEND_LOCKFS_FLAG and/or DM_SUSPEND_NOFLUSH_FLAG
 * @task_state: e.g. TASK_INTERRUPTIBLE or TASK_UNINTERRUPTIBLE
 * @dmf_suspended_flag: DMF_SUSPENDED or DMF_SUSPENDED_INTERNALLY
 *
 * If __dm_suspend returns 0, the device is completely quiescent
 * now. There is no request-processing activity. All new requests
 * are being added to md->deferred list.
 */
static int __dm_suspend(struct mapped_device *md, struct dm_table *map,
                        unsigned suspend_flags, unsigned int task_state,
                        int dmf_suspended_flag)
{
        bool do_lockfs = suspend_flags & DM_SUSPEND_LOCKFS_FLAG;
        bool noflush = suspend_flags & DM_SUSPEND_NOFLUSH_FLAG;
        int r;

        lockdep_assert_held(&md->suspend_lock);

        /*
         * 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);
        else
                DMDEBUG("%s: suspending with flush", dm_device_name(md));

        /*
         * This gets reverted if there's an error later and the targets
         * provide the .presuspend_undo hook.
         */
        dm_table_presuspend_targets(map);

        /*
         * Flush I/O to the device.
         * Any I/O submitted after lock_fs() may not be flushed.
         * noflush takes precedence over do_lockfs.
         * (lock_fs() flushes I/Os and waits for them to complete.)
         */
        if (!noflush && do_lockfs) {
                r = lock_fs(md);
                if (r) {
                        dm_table_presuspend_undo_targets(map);
                        return r;
                }
        }

        /*
         * Here we must make sure that no processes are submitting requests
         * to target drivers i.e. no one may be executing
         * dm_split_and_process_bio from dm_submit_bio.
         *
         * To get all processes out of dm_split_and_process_bio in dm_submit_bio,
         * we take the write lock. To prevent any process from reentering
         * dm_split_and_process_bio from dm_submit_bio and quiesce the thread
         * (dm_wq_work), we set DMF_BLOCK_IO_FOR_SUSPEND and call
         * flush_workqueue(md->wq).
         */
        set_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags);
        if (map)
                synchronize_srcu(&md->io_barrier);

        /*
         * Stop md->queue before flushing md->wq in case request-based
         * dm defers requests to md->wq from md->queue.
         */
        if (dm_request_based(md))
                dm_stop_queue(md->queue);

        flush_workqueue(md->wq);

        /*
         * At this point no more requests are entering target request routines.
         * We call dm_wait_for_completion to wait for all existing requests
         * to finish.
         */
        r = dm_wait_for_completion(md, task_state);
        if (!r)
                set_bit(dmf_suspended_flag, &md->flags);

        if (noflush)
                clear_bit(DMF_NOFLUSH_SUSPENDING, &md->flags);
        if (map)
                synchronize_srcu(&md->io_barrier);

        /* were we interrupted ? */
        if (r < 0) {
                dm_queue_flush(md);

                if (dm_request_based(md))
                        dm_start_queue(md->queue);

                unlock_fs(md);
                dm_table_presuspend_undo_targets(map);
                /* pushback list is already flushed, so skip flush */
        }

        return r;
}

/*
 * 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.
 */
/*
 * Suspend mechanism in request-based dm.
 *
 * 1. Flush all I/Os by lock_fs() if needed.
 * 2. Stop dispatching any I/O by stopping the request_queue.
 * 3. Wait for all in-flight I/Os to be completed or requeued.
 *
 * To abort suspend, start the request_queue.
 */
int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
{
        struct dm_table *map = NULL;
        int r = 0;

retry:
        mutex_lock_nested(&md->suspend_lock, SINGLE_DEPTH_NESTING);

        if (dm_suspended_md(md)) {
                r = -EINVAL;
                goto out_unlock;
        }

        if (dm_suspended_internally_md(md)) {
                /* already internally suspended, wait for internal resume */
                mutex_unlock(&md->suspend_lock);
                r = wait_on_bit(&md->flags, DMF_SUSPENDED_INTERNALLY, TASK_INTERRUPTIBLE);
                if (r)
                        return r;
                goto retry;
        }

        map = rcu_dereference_protected(md->map, lockdep_is_held(&md->suspend_lock));

        r = __dm_suspend(md, map, suspend_flags, TASK_INTERRUPTIBLE, DMF_SUSPENDED);
        if (r)
                goto out_unlock;

        set_bit(DMF_POST_SUSPENDING, &md->flags);
        dm_table_postsuspend_targets(map);
        clear_bit(DMF_POST_SUSPENDING, &md->flags);

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

static int __dm_resume(struct mapped_device *md, struct dm_table *map)
{
        if (map) {
                int r = dm_table_resume_targets(map);
                if (r)
                        return r;
        }

        dm_queue_flush(md);

        /*
         * Flushing deferred I/Os must be done after targets are resumed
         * so that mapping of targets can work correctly.
         * Request-based dm is queueing the deferred I/Os in its request_queue.
         */
        if (dm_request_based(md))
                dm_start_queue(md->queue);

        unlock_fs(md);

        return 0;
}

int dm_resume(struct mapped_device *md)
{
        int r;
        struct dm_table *map = NULL;

retry:
        r = -EINVAL;
        mutex_lock_nested(&md->suspend_lock, SINGLE_DEPTH_NESTING);

        if (!dm_suspended_md(md))
                goto out;

        if (dm_suspended_internally_md(md)) {
                /* already internally suspended, wait for internal resume */
                mutex_unlock(&md->suspend_lock);
                r = wait_on_bit(&md->flags, DMF_SUSPENDED_INTERNALLY, TASK_INTERRUPTIBLE);
                if (r)
                        return r;
                goto retry;
        }

        map = rcu_dereference_protected(md->map, lockdep_is_held(&md->suspend_lock));
        if (!map || !dm_table_get_size(map))
                goto out;

        r = __dm_resume(md, map);
        if (r)
                goto out;

        clear_bit(DMF_SUSPENDED, &md->flags);
out:
        mutex_unlock(&md->suspend_lock);

        return r;
}

/*
 * Internal suspend/resume works like userspace-driven suspend. It waits
 * until all bios finish and prevents issuing new bios to the target drivers.
 * It may be used only from the kernel.
 */

static void __dm_internal_suspend(struct mapped_device *md, unsigned suspend_flags)
{
        struct dm_table *map = NULL;

        lockdep_assert_held(&md->suspend_lock);

        if (md->internal_suspend_count++)
                return; /* nested internal suspend */

        if (dm_suspended_md(md)) {
                set_bit(DMF_SUSPENDED_INTERNALLY, &md->flags);
                return; /* nest suspend */
        }

        map = rcu_dereference_protected(md->map, lockdep_is_held(&md->suspend_lock));

        /*
         * Using TASK_UNINTERRUPTIBLE because only NOFLUSH internal suspend is
         * supported.  Properly supporting a TASK_INTERRUPTIBLE internal suspend
         * would require changing .presuspend to return an error -- avoid this
         * until there is a need for more elaborate variants of internal suspend.
         */
        (void) __dm_suspend(md, map, suspend_flags, TASK_UNINTERRUPTIBLE,
                            DMF_SUSPENDED_INTERNALLY);

        set_bit(DMF_POST_SUSPENDING, &md->flags);
        dm_table_postsuspend_targets(map);
        clear_bit(DMF_POST_SUSPENDING, &md->flags);
}

static void __dm_internal_resume(struct mapped_device *md)
{
        BUG_ON(!md->internal_suspend_count);

        if (--md->internal_suspend_count)
                return; /* resume from nested internal suspend */

        if (dm_suspended_md(md))
                goto done; /* resume from nested suspend */

        /*
         * NOTE: existing callers don't need to call dm_table_resume_targets
         * (which may fail -- so best to avoid it for now by passing NULL map)
         */
        (void) __dm_resume(md, NULL);

done:
        clear_bit(DMF_SUSPENDED_INTERNALLY, &md->flags);
        smp_mb__after_atomic();
        wake_up_bit(&md->flags, DMF_SUSPENDED_INTERNALLY);
}

void dm_internal_suspend_noflush(struct mapped_device *md)
{
        mutex_lock(&md->suspend_lock);
        __dm_internal_suspend(md, DM_SUSPEND_NOFLUSH_FLAG);
        mutex_unlock(&md->suspend_lock);
}
EXPORT_SYMBOL_GPL(dm_internal_suspend_noflush);

void dm_internal_resume(struct mapped_device *md)
{
        mutex_lock(&md->suspend_lock);
        __dm_internal_resume(md);
        mutex_unlock(&md->suspend_lock);
}
EXPORT_SYMBOL_GPL(dm_internal_resume);

/*
 * Fast variants of internal suspend/resume hold md->suspend_lock,
 * which prevents interaction with userspace-driven suspend.
 */

void dm_internal_suspend_fast(struct mapped_device *md)
{
        mutex_lock(&md->suspend_lock);
        if (dm_suspended_md(md) || dm_suspended_internally_md(md))
                return;

        set_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags);
        synchronize_srcu(&md->io_barrier);
        flush_workqueue(md->wq);
        dm_wait_for_completion(md, TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL_GPL(dm_internal_suspend_fast);

void dm_internal_resume_fast(struct mapped_device *md)
{
        if (dm_suspended_md(md) || dm_suspended_internally_md(md))
                goto done;

        dm_queue_flush(md);

done:
        mutex_unlock(&md->suspend_lock);
}
EXPORT_SYMBOL_GPL(dm_internal_resume_fast);

/*-----------------------------------------------------------------
 * Event notification.
 *---------------------------------------------------------------*/
int dm_kobject_uevent(struct mapped_device *md, enum kobject_action action,
                      unsigned cookie, bool need_resize_uevent)
{
        int r;
        unsigned noio_flag;
        char udev_cookie[DM_COOKIE_LENGTH];
        char *envp[3] = { NULL, NULL, NULL };
        char **envpp = envp;
        if (cookie) {
                snprintf(udev_cookie, DM_COOKIE_LENGTH, "%s=%u",
                         DM_COOKIE_ENV_VAR_NAME, cookie);
                *envpp++ = udev_cookie;
        }
        if (need_resize_uevent) {
                *envpp++ = "RESIZE=1";
        }

        noio_flag = memalloc_noio_save();

        r = kobject_uevent_env(&disk_to_dev(md->disk)->kobj, action, envp);

        memalloc_noio_restore(noio_flag);

        return r;
}

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;
}
EXPORT_SYMBOL_GPL(dm_disk);

struct kobject *dm_kobject(struct mapped_device *md)
{
        return &md->kobj_holder.kobj;
}

struct mapped_device *dm_get_from_kobject(struct kobject *kobj)
{
        struct mapped_device *md;

        md = container_of(kobj, struct mapped_device, kobj_holder.kobj);

        spin_lock(&_minor_lock);
        if (test_bit(DMF_FREEING, &md->flags) || dm_deleting_md(md)) {
                md = NULL;
                goto out;
        }
        dm_get(md);
out:
        spin_unlock(&_minor_lock);

        return md;
}

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

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

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

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

int dm_suspended(struct dm_target *ti)
{
        return dm_suspended_md(ti->table->md);
}
EXPORT_SYMBOL_GPL(dm_suspended);

int dm_post_suspending(struct dm_target *ti)
{
        return dm_post_suspending_md(ti->table->md);
}
EXPORT_SYMBOL_GPL(dm_post_suspending);

int dm_noflush_suspending(struct dm_target *ti)
{
        return __noflush_suspending(ti->table->md);
}
EXPORT_SYMBOL_GPL(dm_noflush_suspending);

void dm_free_md_mempools(struct dm_md_mempools *pools)
{
        if (!pools)
                return;

        bioset_exit(&pools->bs);
        bioset_exit(&pools->io_bs);

        kfree(pools);
}

struct dm_pr {
        u64     old_key;
        u64     new_key;
        u32     flags;
        bool    abort;
        bool    fail_early;
        int     ret;
        enum pr_type type;
};

static int dm_call_pr(struct block_device *bdev, iterate_devices_callout_fn fn,
                      struct dm_pr *pr)
{
        struct mapped_device *md = bdev->bd_disk->private_data;
        struct dm_table *table;
        struct dm_target *ti;
        int ret = -ENOTTY, srcu_idx;

        table = dm_get_live_table(md, &srcu_idx);
        if (!table || !dm_table_get_size(table))
                goto out;

        /* We only support devices that have a single target */
        if (table->num_targets != 1)
                goto out;
        ti = dm_table_get_target(table, 0);

        if (dm_suspended_md(md)) {
                ret = -EAGAIN;
                goto out;
        }

        ret = -EINVAL;
        if (!ti->type->iterate_devices)
                goto out;

        ti->type->iterate_devices(ti, fn, pr);
        ret = 0;
out:
        dm_put_live_table(md, srcu_idx);
        return ret;
}

/*
 * For register / unregister we need to manually call out to every path.
 */
static int __dm_pr_register(struct dm_target *ti, struct dm_dev *dev,
                            sector_t start, sector_t len, void *data)
{
        struct dm_pr *pr = data;
        const struct pr_ops *ops = dev->bdev->bd_disk->fops->pr_ops;
        int ret;

        if (!ops || !ops->pr_register) {
                pr->ret = -EOPNOTSUPP;
                return -1;
        }

        ret = ops->pr_register(dev->bdev, pr->old_key, pr->new_key, pr->flags);
        if (!ret)
                return 0;

        if (!pr->ret)
                pr->ret = ret;

        if (pr->fail_early)
                return -1;

        return 0;
}

static int dm_pr_register(struct block_device *bdev, u64 old_key, u64 new_key,
                          u32 flags)
{
        struct dm_pr pr = {
                .old_key        = old_key,
                .new_key        = new_key,
                .flags          = flags,
                .fail_early     = true,
                .ret            = 0,
        };
        int ret;

        ret = dm_call_pr(bdev, __dm_pr_register, &pr);
        if (ret) {
                /* Didn't even get to register a path */
                return ret;
        }

        if (!pr.ret)
                return 0;
        ret = pr.ret;

        if (!new_key)
                return ret;

        /* unregister all paths if we failed to register any path */
        pr.old_key = new_key;
        pr.new_key = 0;
        pr.flags = 0;
        pr.fail_early = false;
        (void) dm_call_pr(bdev, __dm_pr_register, &pr);
        return ret;
}


static int __dm_pr_reserve(struct dm_target *ti, struct dm_dev *dev,
                           sector_t start, sector_t len, void *data)
{
        struct dm_pr *pr = data;
        const struct pr_ops *ops = dev->bdev->bd_disk->fops->pr_ops;

        if (!ops || !ops->pr_reserve) {
                pr->ret = -EOPNOTSUPP;
                return -1;
        }

        pr->ret = ops->pr_reserve(dev->bdev, pr->old_key, pr->type, pr->flags);
        if (!pr->ret)
                return -1;

        return 0;
}

static int dm_pr_reserve(struct block_device *bdev, u64 key, enum pr_type type,
                         u32 flags)
{
        struct dm_pr pr = {
                .old_key        = key,
                .flags          = flags,
                .type           = type,
                .fail_early     = false,
                .ret            = 0,
        };
        int ret;

        ret = dm_call_pr(bdev, __dm_pr_reserve, &pr);
        if (ret)
                return ret;

        return pr.ret;
}

/*
 * If there is a non-All Registrants type of reservation, the release must be
 * sent down the holding path. For the cases where there is no reservation or
 * the path is not the holder the device will also return success, so we must
 * try each path to make sure we got the correct path.
 */
static int __dm_pr_release(struct dm_target *ti, struct dm_dev *dev,
                           sector_t start, sector_t len, void *data)
{
        struct dm_pr *pr = data;
        const struct pr_ops *ops = dev->bdev->bd_disk->fops->pr_ops;

        if (!ops || !ops->pr_release) {
                pr->ret = -EOPNOTSUPP;
                return -1;
        }

        pr->ret = ops->pr_release(dev->bdev, pr->old_key, pr->type);
        if (pr->ret)
                return -1;

        return 0;
}

static int dm_pr_release(struct block_device *bdev, u64 key, enum pr_type type)
{
        struct dm_pr pr = {
                .old_key        = key,
                .type           = type,
                .fail_early     = false,
        };
        int ret;

        ret = dm_call_pr(bdev, __dm_pr_release, &pr);
        if (ret)
                return ret;

        return pr.ret;
}

static int __dm_pr_preempt(struct dm_target *ti, struct dm_dev *dev,
                           sector_t start, sector_t len, void *data)
{
        struct dm_pr *pr = data;
        const struct pr_ops *ops = dev->bdev->bd_disk->fops->pr_ops;

        if (!ops || !ops->pr_preempt) {
                pr->ret = -EOPNOTSUPP;
                return -1;
        }

        pr->ret = ops->pr_preempt(dev->bdev, pr->old_key, pr->new_key, pr->type,
                                  pr->abort);
        if (!pr->ret)
                return -1;

        return 0;
}

static int dm_pr_preempt(struct block_device *bdev, u64 old_key, u64 new_key,
                         enum pr_type type, bool abort)
{
        struct dm_pr pr = {
                .new_key        = new_key,
                .old_key        = old_key,
                .type           = type,
                .fail_early     = false,
        };
        int ret;

        ret = dm_call_pr(bdev, __dm_pr_preempt, &pr);
        if (ret)
                return ret;

        return pr.ret;
}

static int dm_pr_clear(struct block_device *bdev, u64 key)
{
        struct mapped_device *md = bdev->bd_disk->private_data;
        const struct pr_ops *ops;
        int r, srcu_idx;

        r = dm_prepare_ioctl(md, &srcu_idx, &bdev);
        if (r < 0)
                goto out;

        ops = bdev->bd_disk->fops->pr_ops;
        if (ops && ops->pr_clear)
                r = ops->pr_clear(bdev, key);
        else
                r = -EOPNOTSUPP;
out:
        dm_unprepare_ioctl(md, srcu_idx);
        return r;
}

static const struct pr_ops dm_pr_ops = {
        .pr_register    = dm_pr_register,
        .pr_reserve     = dm_pr_reserve,
        .pr_release     = dm_pr_release,
        .pr_preempt     = dm_pr_preempt,
        .pr_clear       = dm_pr_clear,
};

static const struct block_device_operations dm_blk_dops = {
        .submit_bio = dm_submit_bio,
        .poll_bio = dm_poll_bio,
        .open = dm_blk_open,
        .release = dm_blk_close,
        .ioctl = dm_blk_ioctl,
        .getgeo = dm_blk_getgeo,
        .report_zones = dm_blk_report_zones,
        .pr_ops = &dm_pr_ops,
        .owner = THIS_MODULE
};

static const struct block_device_operations dm_rq_blk_dops = {
        .open = dm_blk_open,
        .release = dm_blk_close,
        .ioctl = dm_blk_ioctl,
        .getgeo = dm_blk_getgeo,
        .pr_ops = &dm_pr_ops,
        .owner = THIS_MODULE
};

static const struct dax_operations dm_dax_ops = {
        .direct_access = dm_dax_direct_access,
        .zero_page_range = dm_dax_zero_page_range,
        .recovery_write = dm_dax_recovery_write,
};

/*
 * 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_param(reserved_bio_based_ios, uint, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(reserved_bio_based_ios, "Reserved IOs in bio-based mempools");

module_param(dm_numa_node, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(dm_numa_node, "NUMA node for DM device memory allocations");

module_param(swap_bios, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(swap_bios, "Maximum allowed inflight swap IOs");

MODULE_DESCRIPTION(DM_NAME " driver");
MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
MODULE_LICENSE("GPL");