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dm: implement REQ_FLUSH/FUA support for bio-based dm

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This patch converts bio-based dm to support REQ_FLUSH/FUA instead of
now deprecated REQ_HARDBARRIER.

* -EOPNOTSUPP handling logic dropped.

* Preflush is handled as before but postflush is dropped and replaced
  with passing down REQ_FUA to member request_queues.  This replaces
  one array wide cache flush w/ member specific FUA writes.

* __split_and_process_bio() now calls __clone_and_map_flush() directly
  for flushes and guarantees all FLUSH bio's going to targets are zero
`  length.

* It's now guaranteed that all FLUSH bio's which are passed onto dm
  targets are zero length.  bio_empty_barrier() tests are replaced
  with REQ_FLUSH tests.

* Empty WRITE_BARRIERs are replaced with WRITE_FLUSHes.

* Dropped unlikely() around REQ_FLUSH tests.  Flushes are not unlikely
  enough to be marked with unlikely().

* Block layer now filters out REQ_FLUSH/FUA bio's if the request_queue
  doesn't support cache flushing.  Advertise REQ_FLUSH | REQ_FUA
  capability.

* Request based dm isn't converted yet.  dm_init_request_based_queue()
  resets flush support to 0 for now.  To avoid disturbing request
  based dm code, dm->flush_error is added for bio based dm while
  requested based dm continues to use dm->barrier_error.

Lightly tested linear, stripe, raid1, snap and crypt targets.  Please
proceed with caution as I'm not familiar with the code base.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: dm-devel@redhat.com
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Tejun Heo
2010-09-03 11:56:19 +02:00
committed by Jens Axboe
parent 3a2edd0d6d
commit d87f4c14f2
9 changed files with 80 additions and 97 deletions
Download Patch File Download Diff File Expand all files Collapse all files

119
drivers/md/dm.c
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@@ -144,15 +144,16 @@ struct mapped_device {
spinlock_t deferred_lock;
/*
* An error from the barrier request currently being processed.
* An error from the flush request currently being processed.
*/
int barrier_error;
int flush_error;
/*
* Protect barrier_error from concurrent endio processing
* in request-based dm.
*/
spinlock_t barrier_error_lock;
int barrier_error;
/*
* Processing queue (flush/barriers)
@@ -200,8 +201,8 @@ struct mapped_device {
/* sysfs handle */
struct kobject kobj;
/* zero-length barrier that will be cloned and submitted to targets */
struct bio barrier_bio;
/* zero-length flush that will be cloned and submitted to targets */
struct bio flush_bio;
};
/*
@@ -512,7 +513,7 @@ static void end_io_acct(struct dm_io *io)
/*
* After this is decremented the bio must not be touched if it is
* a barrier.
* a flush.
*/
dm_disk(md)->part0.in_flight[rw] = pending =
atomic_dec_return(&md->pending[rw]);
@@ -626,7 +627,7 @@ static void dec_pending(struct dm_io *io, int error)
*/
spin_lock_irqsave(&md->deferred_lock, flags);
if (__noflush_suspending(md)) {
if (!(io->bio->bi_rw & REQ_HARDBARRIER))
if (!(io->bio->bi_rw & REQ_FLUSH))
bio_list_add_head(&md->deferred,
io->bio);
} else
@@ -638,20 +639,14 @@ static void dec_pending(struct dm_io *io, int error)
io_error = io->error;
bio = io->bio;
if (bio->bi_rw & REQ_HARDBARRIER) {
if (bio->bi_rw & REQ_FLUSH) {
/*
* There can be just one barrier request so we use
* There can be just one flush request so we use
* a per-device variable for error reporting.
* Note that you can't touch the bio after end_io_acct
*
* We ignore -EOPNOTSUPP for empty flush reported by
* underlying devices. We assume that if the device
* doesn't support empty barriers, it doesn't need
* cache flushing commands.
*/
if (!md->barrier_error &&
!(bio_empty_barrier(bio) && io_error == -EOPNOTSUPP))
md->barrier_error = io_error;
if (!md->flush_error)
md->flush_error = io_error;
end_io_acct(io);
free_io(md, io);
} else {
@@ -1119,7 +1114,7 @@ static void dm_bio_destructor(struct bio *bio)
}
/*
* Creates a little bio that is just does part of a bvec.
* Creates a little bio that just does part of a bvec.
*/
static struct bio *split_bvec(struct bio *bio, sector_t sector,
unsigned short idx, unsigned int offset,
@@ -1134,7 +1129,7 @@ static struct bio *split_bvec(struct bio *bio, sector_t sector,
clone->bi_sector = sector;
clone->bi_bdev = bio->bi_bdev;
clone->bi_rw = bio->bi_rw & ~REQ_HARDBARRIER;
clone->bi_rw = bio->bi_rw;
clone->bi_vcnt = 1;
clone->bi_size = to_bytes(len);
clone->bi_io_vec->bv_offset = offset;
@@ -1161,7 +1156,6 @@ static struct bio *clone_bio(struct bio *bio, sector_t sector,
clone = bio_alloc_bioset(GFP_NOIO, bio->bi_max_vecs, bs);
__bio_clone(clone, bio);
clone->bi_rw &= ~REQ_HARDBARRIER;
clone->bi_destructor = dm_bio_destructor;
clone->bi_sector = sector;
clone->bi_idx = idx;
@@ -1225,7 +1219,7 @@ static void __issue_target_requests(struct clone_info *ci, struct dm_target *ti,
__issue_target_request(ci, ti, request_nr, len);
}
static int __clone_and_map_empty_barrier(struct clone_info *ci)
static int __clone_and_map_flush(struct clone_info *ci)
{
unsigned target_nr = 0;
struct dm_target *ti;
@@ -1289,9 +1283,6 @@ static int __clone_and_map(struct clone_info *ci)
sector_t len = 0, max;
struct dm_target_io *tio;
if (unlikely(bio_empty_barrier(bio)))
return __clone_and_map_empty_barrier(ci);
if (unlikely(bio->bi_rw & REQ_DISCARD))
return __clone_and_map_discard(ci);
@@ -1383,11 +1374,11 @@ static void __split_and_process_bio(struct mapped_device *md, struct bio *bio)
ci.map = dm_get_live_table(md);
if (unlikely(!ci.map)) {
if (!(bio->bi_rw & REQ_HARDBARRIER))
if (!(bio->bi_rw & REQ_FLUSH))
bio_io_error(bio);
else
if (!md->barrier_error)
md->barrier_error = -EIO;
if (!md->flush_error)
md->flush_error = -EIO;
return;
}
@@ -1400,14 +1391,22 @@ static void __split_and_process_bio(struct mapped_device *md, struct bio *bio)
ci.io->md = md;
spin_lock_init(&ci.io->endio_lock);
ci.sector = bio->bi_sector;
ci.sector_count = bio_sectors(bio);
if (unlikely(bio_empty_barrier(bio)))
if (!(bio->bi_rw & REQ_FLUSH))
ci.sector_count = bio_sectors(bio);
else {
/* all FLUSH bio's reaching here should be empty */
WARN_ON_ONCE(bio_has_data(bio));
ci.sector_count = 1;
}
ci.idx = bio->bi_idx;
start_io_acct(ci.io);
while (ci.sector_count && !error)
error = __clone_and_map(&ci);
while (ci.sector_count && !error) {
if (!(bio->bi_rw & REQ_FLUSH))
error = __clone_and_map(&ci);
else
error = __clone_and_map_flush(&ci);
}
/* drop the extra reference count */
dec_pending(ci.io, error);
@@ -1492,11 +1491,11 @@ static int _dm_request(struct request_queue *q, struct bio *bio)
part_stat_unlock();
/*
* If we're suspended or the thread is processing barriers
* If we're suspended or the thread is processing flushes
* we have to queue this io for later.
*/
if (unlikely(test_bit(DMF_QUEUE_IO_TO_THREAD, &md->flags)) ||
unlikely(bio->bi_rw & REQ_HARDBARRIER)) {
(bio->bi_rw & REQ_FLUSH)) {
up_read(&md->io_lock);
if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)) &&
@@ -1940,6 +1939,7 @@ static void dm_init_md_queue(struct mapped_device *md)
blk_queue_bounce_limit(md->queue, BLK_BOUNCE_ANY);
md->queue->unplug_fn = dm_unplug_all;
blk_queue_merge_bvec(md->queue, dm_merge_bvec);
blk_queue_flush(md->queue, REQ_FLUSH | REQ_FUA);
}
/*
@@ -2245,7 +2245,8 @@ static int dm_init_request_based_queue(struct mapped_device *md)
blk_queue_softirq_done(md->queue, dm_softirq_done);
blk_queue_prep_rq(md->queue, dm_prep_fn);
blk_queue_lld_busy(md->queue, dm_lld_busy);
blk_queue_flush(md->queue, REQ_FLUSH);
/* no flush support for request based dm yet */
blk_queue_flush(md->queue, 0);
elv_register_queue(md->queue);
@@ -2406,41 +2407,35 @@ static int dm_wait_for_completion(struct mapped_device *md, int interruptible)
return r;
}
static void dm_flush(struct mapped_device *md)
static void process_flush(struct mapped_device *md, struct bio *bio)
{
md->flush_error = 0;
/* handle REQ_FLUSH */
dm_wait_for_completion(md, TASK_UNINTERRUPTIBLE);
bio_init(&md->barrier_bio);
md->barrier_bio.bi_bdev = md->bdev;
md->barrier_bio.bi_rw = WRITE_BARRIER;
__split_and_process_bio(md, &md->barrier_bio);
bio_init(&md->flush_bio);
md->flush_bio.bi_bdev = md->bdev;
md->flush_bio.bi_rw = WRITE_FLUSH;
__split_and_process_bio(md, &md->flush_bio);
dm_wait_for_completion(md, TASK_UNINTERRUPTIBLE);
}
static void process_barrier(struct mapped_device *md, struct bio *bio)
{
md->barrier_error = 0;
dm_flush(md);
if (!bio_empty_barrier(bio)) {
__split_and_process_bio(md, bio);
/*
* If the request isn't supported, don't waste time with
* the second flush.
*/
if (md->barrier_error != -EOPNOTSUPP)
dm_flush(md);
/* if it's an empty flush or the preflush failed, we're done */
if (!bio_has_data(bio) || md->flush_error) {
if (md->flush_error != DM_ENDIO_REQUEUE)
bio_endio(bio, md->flush_error);
else {
spin_lock_irq(&md->deferred_lock);
bio_list_add_head(&md->deferred, bio);
spin_unlock_irq(&md->deferred_lock);
}
return;
}
if (md->barrier_error != DM_ENDIO_REQUEUE)
bio_endio(bio, md->barrier_error);
else {
spin_lock_irq(&md->deferred_lock);
bio_list_add_head(&md->deferred, bio);
spin_unlock_irq(&md->deferred_lock);
}
/* issue data + REQ_FUA */
bio->bi_rw &= ~REQ_FLUSH;
__split_and_process_bio(md, bio);
}
/*
@@ -2469,8 +2464,8 @@ static void dm_wq_work(struct work_struct *work)
if (dm_request_based(md))
generic_make_request(c);
else {
if (c->bi_rw & REQ_HARDBARRIER)
process_barrier(md, c);
if (c->bi_rw & REQ_FLUSH)
process_flush(md, c);
else
__split_and_process_bio(md, c);
}