linux/drivers/md/dm-log-writes.c
Linus Torvalds 1e1a4e8f43 Merge tag 'dm-4.3-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device mapper update from Mike Snitzer:

 - a couple small cleanups in dm-cache, dm-verity, persistent-data's
   dm-btree, and DM core.

 - a 4.1-stable fix for dm-cache that fixes the leaking of deferred bio
   prison cells

 - a 4.2-stable fix that adds feature reporting for the dm-stats
   features added in 4.2

 - improve DM-snapshot to not invalidate the on-disk snapshot if
   snapshot device write overflow occurs; but a write overflow triggered
   through the origin device will still invalidate the snapshot.

 - optimize DM-thinp's async discard submission a bit now that late bio
   splitting has been included in block core.

 - switch DM-cache's SMQ policy lock from using a mutex to a spinlock;
   improves performance on very low latency devices (eg. NVMe SSD).

 - document DM RAID 4/5/6's discard support

[ I did not pull the slab changes, which weren't appropriate for this
  tree, and weren't obviously the right thing to do anyway.  At the very
  least they need some discussion and explanation before getting merged.

  Because not pulling the actual tagged commit but doing a partial pull
  instead, this merge commit thus also obviously is missing the git
  signature from the original tag ]

* tag 'dm-4.3-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
  dm cache: fix use after freeing migrations
  dm cache: small cleanups related to deferred prison cell cleanup
  dm cache: fix leaking of deferred bio prison cells
  dm raid: document RAID 4/5/6 discard support
  dm stats: report precise_timestamps and histogram in @stats_list output
  dm thin: optimize async discard submission
  dm snapshot: don't invalidate on-disk image on snapshot write overflow
  dm: remove unlikely() before IS_ERR()
  dm: do not override error code returned from dm_get_device()
  dm: test return value for DM_MAPIO_SUBMITTED
  dm verity: remove unused mempool
  dm cache: move wake_waker() from free_migrations() to where it is needed
  dm btree remove: remove unused function get_nr_entries()
  dm btree: remove unused "dm_block_t root" parameter in btree_split_sibling()
  dm cache policy smq: change the mutex to a spinlock
2015-09-02 16:35:26 -07:00

812 lines
20 KiB
C

/*
* Copyright (C) 2014 Facebook. All rights reserved.
*
* This file is released under the GPL.
*/
#include <linux/device-mapper.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/blkdev.h>
#include <linux/bio.h>
#include <linux/slab.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#define DM_MSG_PREFIX "log-writes"
/*
* This target will sequentially log all writes to the target device onto the
* log device. This is helpful for replaying writes to check for fs consistency
* at all times. This target provides a mechanism to mark specific events to
* check data at a later time. So for example you would:
*
* write data
* fsync
* dmsetup message /dev/whatever mark mymark
* unmount /mnt/test
*
* Then replay the log up to mymark and check the contents of the replay to
* verify it matches what was written.
*
* We log writes only after they have been flushed, this makes the log describe
* close to the order in which the data hits the actual disk, not its cache. So
* for example the following sequence (W means write, C means complete)
*
* Wa,Wb,Wc,Cc,Ca,FLUSH,FUAd,Cb,CFLUSH,CFUAd
*
* Would result in the log looking like this:
*
* c,a,flush,fuad,b,<other writes>,<next flush>
*
* This is meant to help expose problems where file systems do not properly wait
* on data being written before invoking a FLUSH. FUA bypasses cache so once it
* completes it is added to the log as it should be on disk.
*
* We treat DISCARDs as if they don't bypass cache so that they are logged in
* order of completion along with the normal writes. If we didn't do it this
* way we would process all the discards first and then write all the data, when
* in fact we want to do the data and the discard in the order that they
* completed.
*/
#define LOG_FLUSH_FLAG (1 << 0)
#define LOG_FUA_FLAG (1 << 1)
#define LOG_DISCARD_FLAG (1 << 2)
#define LOG_MARK_FLAG (1 << 3)
#define WRITE_LOG_VERSION 1ULL
#define WRITE_LOG_MAGIC 0x6a736677736872ULL
/*
* The disk format for this is braindead simple.
*
* At byte 0 we have our super, followed by the following sequence for
* nr_entries:
*
* [ 1 sector ][ entry->nr_sectors ]
* [log_write_entry][ data written ]
*
* The log_write_entry takes up a full sector so we can have arbitrary length
* marks and it leaves us room for extra content in the future.
*/
/*
* Basic info about the log for userspace.
*/
struct log_write_super {
__le64 magic;
__le64 version;
__le64 nr_entries;
__le32 sectorsize;
};
/*
* sector - the sector we wrote.
* nr_sectors - the number of sectors we wrote.
* flags - flags for this log entry.
* data_len - the size of the data in this log entry, this is for private log
* entry stuff, the MARK data provided by userspace for example.
*/
struct log_write_entry {
__le64 sector;
__le64 nr_sectors;
__le64 flags;
__le64 data_len;
};
struct log_writes_c {
struct dm_dev *dev;
struct dm_dev *logdev;
u64 logged_entries;
u32 sectorsize;
atomic_t io_blocks;
atomic_t pending_blocks;
sector_t next_sector;
sector_t end_sector;
bool logging_enabled;
bool device_supports_discard;
spinlock_t blocks_lock;
struct list_head unflushed_blocks;
struct list_head logging_blocks;
wait_queue_head_t wait;
struct task_struct *log_kthread;
};
struct pending_block {
int vec_cnt;
u64 flags;
sector_t sector;
sector_t nr_sectors;
char *data;
u32 datalen;
struct list_head list;
struct bio_vec vecs[0];
};
struct per_bio_data {
struct pending_block *block;
};
static void put_pending_block(struct log_writes_c *lc)
{
if (atomic_dec_and_test(&lc->pending_blocks)) {
smp_mb__after_atomic();
if (waitqueue_active(&lc->wait))
wake_up(&lc->wait);
}
}
static void put_io_block(struct log_writes_c *lc)
{
if (atomic_dec_and_test(&lc->io_blocks)) {
smp_mb__after_atomic();
if (waitqueue_active(&lc->wait))
wake_up(&lc->wait);
}
}
static void log_end_io(struct bio *bio)
{
struct log_writes_c *lc = bio->bi_private;
struct bio_vec *bvec;
int i;
if (bio->bi_error) {
unsigned long flags;
DMERR("Error writing log block, error=%d", bio->bi_error);
spin_lock_irqsave(&lc->blocks_lock, flags);
lc->logging_enabled = false;
spin_unlock_irqrestore(&lc->blocks_lock, flags);
}
bio_for_each_segment_all(bvec, bio, i)
__free_page(bvec->bv_page);
put_io_block(lc);
bio_put(bio);
}
/*
* Meant to be called if there is an error, it will free all the pages
* associated with the block.
*/
static void free_pending_block(struct log_writes_c *lc,
struct pending_block *block)
{
int i;
for (i = 0; i < block->vec_cnt; i++) {
if (block->vecs[i].bv_page)
__free_page(block->vecs[i].bv_page);
}
kfree(block->data);
kfree(block);
put_pending_block(lc);
}
static int write_metadata(struct log_writes_c *lc, void *entry,
size_t entrylen, void *data, size_t datalen,
sector_t sector)
{
struct bio *bio;
struct page *page;
void *ptr;
size_t ret;
bio = bio_alloc(GFP_KERNEL, 1);
if (!bio) {
DMERR("Couldn't alloc log bio");
goto error;
}
bio->bi_iter.bi_size = 0;
bio->bi_iter.bi_sector = sector;
bio->bi_bdev = lc->logdev->bdev;
bio->bi_end_io = log_end_io;
bio->bi_private = lc;
page = alloc_page(GFP_KERNEL);
if (!page) {
DMERR("Couldn't alloc log page");
bio_put(bio);
goto error;
}
ptr = kmap_atomic(page);
memcpy(ptr, entry, entrylen);
if (datalen)
memcpy(ptr + entrylen, data, datalen);
memset(ptr + entrylen + datalen, 0,
lc->sectorsize - entrylen - datalen);
kunmap_atomic(ptr);
ret = bio_add_page(bio, page, lc->sectorsize, 0);
if (ret != lc->sectorsize) {
DMERR("Couldn't add page to the log block");
goto error_bio;
}
submit_bio(WRITE, bio);
return 0;
error_bio:
bio_put(bio);
__free_page(page);
error:
put_io_block(lc);
return -1;
}
static int log_one_block(struct log_writes_c *lc,
struct pending_block *block, sector_t sector)
{
struct bio *bio;
struct log_write_entry entry;
size_t ret;
int i;
entry.sector = cpu_to_le64(block->sector);
entry.nr_sectors = cpu_to_le64(block->nr_sectors);
entry.flags = cpu_to_le64(block->flags);
entry.data_len = cpu_to_le64(block->datalen);
if (write_metadata(lc, &entry, sizeof(entry), block->data,
block->datalen, sector)) {
free_pending_block(lc, block);
return -1;
}
if (!block->vec_cnt)
goto out;
sector++;
bio = bio_alloc(GFP_KERNEL, block->vec_cnt);
if (!bio) {
DMERR("Couldn't alloc log bio");
goto error;
}
atomic_inc(&lc->io_blocks);
bio->bi_iter.bi_size = 0;
bio->bi_iter.bi_sector = sector;
bio->bi_bdev = lc->logdev->bdev;
bio->bi_end_io = log_end_io;
bio->bi_private = lc;
for (i = 0; i < block->vec_cnt; i++) {
/*
* The page offset is always 0 because we allocate a new page
* for every bvec in the original bio for simplicity sake.
*/
ret = bio_add_page(bio, block->vecs[i].bv_page,
block->vecs[i].bv_len, 0);
if (ret != block->vecs[i].bv_len) {
atomic_inc(&lc->io_blocks);
submit_bio(WRITE, bio);
bio = bio_alloc(GFP_KERNEL, block->vec_cnt - i);
if (!bio) {
DMERR("Couldn't alloc log bio");
goto error;
}
bio->bi_iter.bi_size = 0;
bio->bi_iter.bi_sector = sector;
bio->bi_bdev = lc->logdev->bdev;
bio->bi_end_io = log_end_io;
bio->bi_private = lc;
ret = bio_add_page(bio, block->vecs[i].bv_page,
block->vecs[i].bv_len, 0);
if (ret != block->vecs[i].bv_len) {
DMERR("Couldn't add page on new bio?");
bio_put(bio);
goto error;
}
}
sector += block->vecs[i].bv_len >> SECTOR_SHIFT;
}
submit_bio(WRITE, bio);
out:
kfree(block->data);
kfree(block);
put_pending_block(lc);
return 0;
error:
free_pending_block(lc, block);
put_io_block(lc);
return -1;
}
static int log_super(struct log_writes_c *lc)
{
struct log_write_super super;
super.magic = cpu_to_le64(WRITE_LOG_MAGIC);
super.version = cpu_to_le64(WRITE_LOG_VERSION);
super.nr_entries = cpu_to_le64(lc->logged_entries);
super.sectorsize = cpu_to_le32(lc->sectorsize);
if (write_metadata(lc, &super, sizeof(super), NULL, 0, 0)) {
DMERR("Couldn't write super");
return -1;
}
return 0;
}
static inline sector_t logdev_last_sector(struct log_writes_c *lc)
{
return i_size_read(lc->logdev->bdev->bd_inode) >> SECTOR_SHIFT;
}
static int log_writes_kthread(void *arg)
{
struct log_writes_c *lc = (struct log_writes_c *)arg;
sector_t sector = 0;
while (!kthread_should_stop()) {
bool super = false;
bool logging_enabled;
struct pending_block *block = NULL;
int ret;
spin_lock_irq(&lc->blocks_lock);
if (!list_empty(&lc->logging_blocks)) {
block = list_first_entry(&lc->logging_blocks,
struct pending_block, list);
list_del_init(&block->list);
if (!lc->logging_enabled)
goto next;
sector = lc->next_sector;
if (block->flags & LOG_DISCARD_FLAG)
lc->next_sector++;
else
lc->next_sector += block->nr_sectors + 1;
/*
* Apparently the size of the device may not be known
* right away, so handle this properly.
*/
if (!lc->end_sector)
lc->end_sector = logdev_last_sector(lc);
if (lc->end_sector &&
lc->next_sector >= lc->end_sector) {
DMERR("Ran out of space on the logdev");
lc->logging_enabled = false;
goto next;
}
lc->logged_entries++;
atomic_inc(&lc->io_blocks);
super = (block->flags & (LOG_FUA_FLAG | LOG_MARK_FLAG));
if (super)
atomic_inc(&lc->io_blocks);
}
next:
logging_enabled = lc->logging_enabled;
spin_unlock_irq(&lc->blocks_lock);
if (block) {
if (logging_enabled) {
ret = log_one_block(lc, block, sector);
if (!ret && super)
ret = log_super(lc);
if (ret) {
spin_lock_irq(&lc->blocks_lock);
lc->logging_enabled = false;
spin_unlock_irq(&lc->blocks_lock);
}
} else
free_pending_block(lc, block);
continue;
}
if (!try_to_freeze()) {
set_current_state(TASK_INTERRUPTIBLE);
if (!kthread_should_stop() &&
!atomic_read(&lc->pending_blocks))
schedule();
__set_current_state(TASK_RUNNING);
}
}
return 0;
}
/*
* Construct a log-writes mapping:
* log-writes <dev_path> <log_dev_path>
*/
static int log_writes_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
struct log_writes_c *lc;
struct dm_arg_set as;
const char *devname, *logdevname;
int ret;
as.argc = argc;
as.argv = argv;
if (argc < 2) {
ti->error = "Invalid argument count";
return -EINVAL;
}
lc = kzalloc(sizeof(struct log_writes_c), GFP_KERNEL);
if (!lc) {
ti->error = "Cannot allocate context";
return -ENOMEM;
}
spin_lock_init(&lc->blocks_lock);
INIT_LIST_HEAD(&lc->unflushed_blocks);
INIT_LIST_HEAD(&lc->logging_blocks);
init_waitqueue_head(&lc->wait);
lc->sectorsize = 1 << SECTOR_SHIFT;
atomic_set(&lc->io_blocks, 0);
atomic_set(&lc->pending_blocks, 0);
devname = dm_shift_arg(&as);
ret = dm_get_device(ti, devname, dm_table_get_mode(ti->table), &lc->dev);
if (ret) {
ti->error = "Device lookup failed";
goto bad;
}
logdevname = dm_shift_arg(&as);
ret = dm_get_device(ti, logdevname, dm_table_get_mode(ti->table),
&lc->logdev);
if (ret) {
ti->error = "Log device lookup failed";
dm_put_device(ti, lc->dev);
goto bad;
}
ret = -EINVAL;
lc->log_kthread = kthread_run(log_writes_kthread, lc, "log-write");
if (!lc->log_kthread) {
ti->error = "Couldn't alloc kthread";
dm_put_device(ti, lc->dev);
dm_put_device(ti, lc->logdev);
goto bad;
}
/* We put the super at sector 0, start logging at sector 1 */
lc->next_sector = 1;
lc->logging_enabled = true;
lc->end_sector = logdev_last_sector(lc);
lc->device_supports_discard = true;
ti->num_flush_bios = 1;
ti->flush_supported = true;
ti->num_discard_bios = 1;
ti->discards_supported = true;
ti->per_bio_data_size = sizeof(struct per_bio_data);
ti->private = lc;
return 0;
bad:
kfree(lc);
return ret;
}
static int log_mark(struct log_writes_c *lc, char *data)
{
struct pending_block *block;
size_t maxsize = lc->sectorsize - sizeof(struct log_write_entry);
block = kzalloc(sizeof(struct pending_block), GFP_KERNEL);
if (!block) {
DMERR("Error allocating pending block");
return -ENOMEM;
}
block->data = kstrndup(data, maxsize, GFP_KERNEL);
if (!block->data) {
DMERR("Error copying mark data");
kfree(block);
return -ENOMEM;
}
atomic_inc(&lc->pending_blocks);
block->datalen = strlen(block->data);
block->flags |= LOG_MARK_FLAG;
spin_lock_irq(&lc->blocks_lock);
list_add_tail(&block->list, &lc->logging_blocks);
spin_unlock_irq(&lc->blocks_lock);
wake_up_process(lc->log_kthread);
return 0;
}
static void log_writes_dtr(struct dm_target *ti)
{
struct log_writes_c *lc = ti->private;
spin_lock_irq(&lc->blocks_lock);
list_splice_init(&lc->unflushed_blocks, &lc->logging_blocks);
spin_unlock_irq(&lc->blocks_lock);
/*
* This is just nice to have since it'll update the super to include the
* unflushed blocks, if it fails we don't really care.
*/
log_mark(lc, "dm-log-writes-end");
wake_up_process(lc->log_kthread);
wait_event(lc->wait, !atomic_read(&lc->io_blocks) &&
!atomic_read(&lc->pending_blocks));
kthread_stop(lc->log_kthread);
WARN_ON(!list_empty(&lc->logging_blocks));
WARN_ON(!list_empty(&lc->unflushed_blocks));
dm_put_device(ti, lc->dev);
dm_put_device(ti, lc->logdev);
kfree(lc);
}
static void normal_map_bio(struct dm_target *ti, struct bio *bio)
{
struct log_writes_c *lc = ti->private;
bio->bi_bdev = lc->dev->bdev;
}
static int log_writes_map(struct dm_target *ti, struct bio *bio)
{
struct log_writes_c *lc = ti->private;
struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
struct pending_block *block;
struct bvec_iter iter;
struct bio_vec bv;
size_t alloc_size;
int i = 0;
bool flush_bio = (bio->bi_rw & REQ_FLUSH);
bool fua_bio = (bio->bi_rw & REQ_FUA);
bool discard_bio = (bio->bi_rw & REQ_DISCARD);
pb->block = NULL;
/* Don't bother doing anything if logging has been disabled */
if (!lc->logging_enabled)
goto map_bio;
/*
* Map reads as normal.
*/
if (bio_data_dir(bio) == READ)
goto map_bio;
/* No sectors and not a flush? Don't care */
if (!bio_sectors(bio) && !flush_bio)
goto map_bio;
/*
* Discards will have bi_size set but there's no actual data, so just
* allocate the size of the pending block.
*/
if (discard_bio)
alloc_size = sizeof(struct pending_block);
else
alloc_size = sizeof(struct pending_block) + sizeof(struct bio_vec) * bio_segments(bio);
block = kzalloc(alloc_size, GFP_NOIO);
if (!block) {
DMERR("Error allocating pending block");
spin_lock_irq(&lc->blocks_lock);
lc->logging_enabled = false;
spin_unlock_irq(&lc->blocks_lock);
return -ENOMEM;
}
INIT_LIST_HEAD(&block->list);
pb->block = block;
atomic_inc(&lc->pending_blocks);
if (flush_bio)
block->flags |= LOG_FLUSH_FLAG;
if (fua_bio)
block->flags |= LOG_FUA_FLAG;
if (discard_bio)
block->flags |= LOG_DISCARD_FLAG;
block->sector = bio->bi_iter.bi_sector;
block->nr_sectors = bio_sectors(bio);
/* We don't need the data, just submit */
if (discard_bio) {
WARN_ON(flush_bio || fua_bio);
if (lc->device_supports_discard)
goto map_bio;
bio_endio(bio);
return DM_MAPIO_SUBMITTED;
}
/* Flush bio, splice the unflushed blocks onto this list and submit */
if (flush_bio && !bio_sectors(bio)) {
spin_lock_irq(&lc->blocks_lock);
list_splice_init(&lc->unflushed_blocks, &block->list);
spin_unlock_irq(&lc->blocks_lock);
goto map_bio;
}
/*
* We will write this bio somewhere else way later so we need to copy
* the actual contents into new pages so we know the data will always be
* there.
*
* We do this because this could be a bio from O_DIRECT in which case we
* can't just hold onto the page until some later point, we have to
* manually copy the contents.
*/
bio_for_each_segment(bv, bio, iter) {
struct page *page;
void *src, *dst;
page = alloc_page(GFP_NOIO);
if (!page) {
DMERR("Error allocing page");
free_pending_block(lc, block);
spin_lock_irq(&lc->blocks_lock);
lc->logging_enabled = false;
spin_unlock_irq(&lc->blocks_lock);
return -ENOMEM;
}
src = kmap_atomic(bv.bv_page);
dst = kmap_atomic(page);
memcpy(dst, src + bv.bv_offset, bv.bv_len);
kunmap_atomic(dst);
kunmap_atomic(src);
block->vecs[i].bv_page = page;
block->vecs[i].bv_len = bv.bv_len;
block->vec_cnt++;
i++;
}
/* Had a flush with data in it, weird */
if (flush_bio) {
spin_lock_irq(&lc->blocks_lock);
list_splice_init(&lc->unflushed_blocks, &block->list);
spin_unlock_irq(&lc->blocks_lock);
}
map_bio:
normal_map_bio(ti, bio);
return DM_MAPIO_REMAPPED;
}
static int normal_end_io(struct dm_target *ti, struct bio *bio, int error)
{
struct log_writes_c *lc = ti->private;
struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
if (bio_data_dir(bio) == WRITE && pb->block) {
struct pending_block *block = pb->block;
unsigned long flags;
spin_lock_irqsave(&lc->blocks_lock, flags);
if (block->flags & LOG_FLUSH_FLAG) {
list_splice_tail_init(&block->list, &lc->logging_blocks);
list_add_tail(&block->list, &lc->logging_blocks);
wake_up_process(lc->log_kthread);
} else if (block->flags & LOG_FUA_FLAG) {
list_add_tail(&block->list, &lc->logging_blocks);
wake_up_process(lc->log_kthread);
} else
list_add_tail(&block->list, &lc->unflushed_blocks);
spin_unlock_irqrestore(&lc->blocks_lock, flags);
}
return error;
}
/*
* INFO format: <logged entries> <highest allocated sector>
*/
static void log_writes_status(struct dm_target *ti, status_type_t type,
unsigned status_flags, char *result,
unsigned maxlen)
{
unsigned sz = 0;
struct log_writes_c *lc = ti->private;
switch (type) {
case STATUSTYPE_INFO:
DMEMIT("%llu %llu", lc->logged_entries,
(unsigned long long)lc->next_sector - 1);
if (!lc->logging_enabled)
DMEMIT(" logging_disabled");
break;
case STATUSTYPE_TABLE:
DMEMIT("%s %s", lc->dev->name, lc->logdev->name);
break;
}
}
static int log_writes_ioctl(struct dm_target *ti, unsigned int cmd,
unsigned long arg)
{
struct log_writes_c *lc = ti->private;
struct dm_dev *dev = lc->dev;
int r = 0;
/*
* Only pass ioctls through if the device sizes match exactly.
*/
if (ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
r = scsi_verify_blk_ioctl(NULL, cmd);
return r ? : __blkdev_driver_ioctl(dev->bdev, dev->mode, cmd, arg);
}
static int log_writes_iterate_devices(struct dm_target *ti,
iterate_devices_callout_fn fn,
void *data)
{
struct log_writes_c *lc = ti->private;
return fn(ti, lc->dev, 0, ti->len, data);
}
/*
* Messages supported:
* mark <mark data> - specify the marked data.
*/
static int log_writes_message(struct dm_target *ti, unsigned argc, char **argv)
{
int r = -EINVAL;
struct log_writes_c *lc = ti->private;
if (argc != 2) {
DMWARN("Invalid log-writes message arguments, expect 2 arguments, got %d", argc);
return r;
}
if (!strcasecmp(argv[0], "mark"))
r = log_mark(lc, argv[1]);
else
DMWARN("Unrecognised log writes target message received: %s", argv[0]);
return r;
}
static void log_writes_io_hints(struct dm_target *ti, struct queue_limits *limits)
{
struct log_writes_c *lc = ti->private;
struct request_queue *q = bdev_get_queue(lc->dev->bdev);
if (!q || !blk_queue_discard(q)) {
lc->device_supports_discard = false;
limits->discard_granularity = 1 << SECTOR_SHIFT;
limits->max_discard_sectors = (UINT_MAX >> SECTOR_SHIFT);
}
}
static struct target_type log_writes_target = {
.name = "log-writes",
.version = {1, 0, 0},
.module = THIS_MODULE,
.ctr = log_writes_ctr,
.dtr = log_writes_dtr,
.map = log_writes_map,
.end_io = normal_end_io,
.status = log_writes_status,
.ioctl = log_writes_ioctl,
.message = log_writes_message,
.iterate_devices = log_writes_iterate_devices,
.io_hints = log_writes_io_hints,
};
static int __init dm_log_writes_init(void)
{
int r = dm_register_target(&log_writes_target);
if (r < 0)
DMERR("register failed %d", r);
return r;
}
static void __exit dm_log_writes_exit(void)
{
dm_unregister_target(&log_writes_target);
}
module_init(dm_log_writes_init);
module_exit(dm_log_writes_exit);
MODULE_DESCRIPTION(DM_NAME " log writes target");
MODULE_AUTHOR("Josef Bacik <jbacik@fb.com>");
MODULE_LICENSE("GPL");