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Commit d87f4c14 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
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dm: implement REQ_FLUSH/FUA support for bio-based dm 



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: default avatarTejun Heo <tj@kernel.org>
Cc: dm-devel@redhat.com
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent 3a2edd0d

drivers/md/dm-crypt.c

+1 −1
Original line number Diff line number Diff line
@@ -1278,7 +1278,7 @@ static int crypt_map(struct dm_target *ti, struct bio *bio, 
	struct dm_crypt_io *io;

	struct crypt_config *cc;



	if (unlikely(bio_empty_barrier(bio))) {

	if (bio->bi_rw & REQ_FLUSH) {

		cc = ti->private;

		bio->bi_bdev = cc->dev->bdev;

		return DM_MAPIO_REMAPPED;

drivers/md/dm-io.c

+4 −16
Original line number Diff line number Diff line
@@ -31,7 +31,6 @@ struct dm_io_client { 
 */

struct io {

	unsigned long error_bits;

	unsigned long eopnotsupp_bits;

	atomic_t count;

	struct task_struct *sleeper;

	struct dm_io_client *client;
@@ -130,11 +129,8 @@ static void retrieve_io_and_region_from_bio(struct bio *bio, struct io **io, 
 *---------------------------------------------------------------*/

static void dec_count(struct io *io, unsigned int region, int error)

{

	if (error) {

	if (error)

		set_bit(region, &io->error_bits);

		if (error == -EOPNOTSUPP)

			set_bit(region, &io->eopnotsupp_bits);

	}



	if (atomic_dec_and_test(&io->count)) {

		if (io->sleeper)
@@ -310,8 +306,8 @@ static void do_region(int rw, unsigned region, struct dm_io_region *where, 
	sector_t remaining = where->count;



	/*

	 * where->count may be zero if rw holds a write barrier and we

	 * need to send a zero-sized barrier.

	 * where->count may be zero if rw holds a flush and we need to

	 * send a zero-sized flush.

	 */

	do {

		/*
@@ -364,7 +360,7 @@ static void dispatch_io(int rw, unsigned int num_regions, 
	 */

	for (i = 0; i < num_regions; i++) {

		*dp = old_pages;

		if (where[i].count || (rw & REQ_HARDBARRIER))

		if (where[i].count || (rw & REQ_FLUSH))

			do_region(rw, i, where + i, dp, io);

	}
@@ -393,9 +389,7 @@ static int sync_io(struct dm_io_client *client, unsigned int num_regions, 
		return -EIO;

	}



retry:

	io->error_bits = 0;

	io->eopnotsupp_bits = 0;

	atomic_set(&io->count, 1); /* see dispatch_io() */

	io->sleeper = current;

	io->client = client;
@@ -412,11 +406,6 @@ static int sync_io(struct dm_io_client *client, unsigned int num_regions, 
	}

	set_current_state(TASK_RUNNING);



	if (io->eopnotsupp_bits && (rw & REQ_HARDBARRIER)) {

		rw &= ~REQ_HARDBARRIER;

		goto retry;

	}



	if (error_bits)

		*error_bits = io->error_bits;
@@ -437,7 +426,6 @@ static int async_io(struct dm_io_client *client, unsigned int num_regions, 


	io = mempool_alloc(client->pool, GFP_NOIO);

	io->error_bits = 0;

	io->eopnotsupp_bits = 0;

	atomic_set(&io->count, 1); /* see dispatch_io() */

	io->sleeper = NULL;

	io->client = client;

drivers/md/dm-log.c

+1 −1
Original line number Diff line number Diff line
@@ -300,7 +300,7 @@ static int flush_header(struct log_c *lc) 
		.count = 0,

	};



	lc->io_req.bi_rw = WRITE_BARRIER;

	lc->io_req.bi_rw = WRITE_FLUSH;



	return dm_io(&lc->io_req, 1, &null_location, NULL);

}

drivers/md/dm-raid1.c

+4 −4
Original line number Diff line number Diff line
@@ -259,7 +259,7 @@ static int mirror_flush(struct dm_target *ti) 
	struct dm_io_region io[ms->nr_mirrors];

	struct mirror *m;

	struct dm_io_request io_req = {

		.bi_rw = WRITE_BARRIER,

		.bi_rw = WRITE_FLUSH,

		.mem.type = DM_IO_KMEM,

		.mem.ptr.bvec = NULL,

		.client = ms->io_client,
@@ -629,7 +629,7 @@ static void do_write(struct mirror_set *ms, struct bio *bio) 
	struct dm_io_region io[ms->nr_mirrors], *dest = io;

	struct mirror *m;

	struct dm_io_request io_req = {

		.bi_rw = WRITE | (bio->bi_rw & WRITE_BARRIER),

		.bi_rw = WRITE | (bio->bi_rw & WRITE_FLUSH_FUA),

		.mem.type = DM_IO_BVEC,

		.mem.ptr.bvec = bio->bi_io_vec + bio->bi_idx,

		.notify.fn = write_callback,
@@ -670,7 +670,7 @@ static void do_writes(struct mirror_set *ms, struct bio_list *writes) 
	bio_list_init(&requeue);



	while ((bio = bio_list_pop(writes))) {

		if (unlikely(bio_empty_barrier(bio))) {

		if (bio->bi_rw & REQ_FLUSH) {

			bio_list_add(&sync, bio);

			continue;

		}
@@ -1203,7 +1203,7 @@ static int mirror_end_io(struct dm_target *ti, struct bio *bio, 
	 * We need to dec pending if this was a write.

	 */

	if (rw == WRITE) {

		if (likely(!bio_empty_barrier(bio)))

		if (!(bio->bi_rw & REQ_FLUSH))

			dm_rh_dec(ms->rh, map_context->ll);

		return error;

	}

drivers/md/dm-region-hash.c

+8 −8
Original line number Diff line number Diff line
@@ -81,9 +81,9 @@ struct dm_region_hash { 
	struct list_head failed_recovered_regions;



	/*

	 * If there was a barrier failure no regions can be marked clean.

	 * If there was a flush failure no regions can be marked clean.

	 */

	int barrier_failure;

	int flush_failure;



	void *context;

	sector_t target_begin;
@@ -217,7 +217,7 @@ struct dm_region_hash *dm_region_hash_create( 
	INIT_LIST_HEAD(&rh->quiesced_regions);

	INIT_LIST_HEAD(&rh->recovered_regions);

	INIT_LIST_HEAD(&rh->failed_recovered_regions);

	rh->barrier_failure = 0;

	rh->flush_failure = 0;



	rh->region_pool = mempool_create_kmalloc_pool(MIN_REGIONS,

						      sizeof(struct dm_region));
@@ -399,8 +399,8 @@ void dm_rh_mark_nosync(struct dm_region_hash *rh, struct bio *bio) 
	region_t region = dm_rh_bio_to_region(rh, bio);

	int recovering = 0;



	if (bio_empty_barrier(bio)) {

		rh->barrier_failure = 1;

	if (bio->bi_rw & REQ_FLUSH) {

		rh->flush_failure = 1;

		return;

	}
@@ -524,7 +524,7 @@ void dm_rh_inc_pending(struct dm_region_hash *rh, struct bio_list *bios) 
	struct bio *bio;



	for (bio = bios->head; bio; bio = bio->bi_next) {

		if (bio_empty_barrier(bio))

		if (bio->bi_rw & REQ_FLUSH)

			continue;

		rh_inc(rh, dm_rh_bio_to_region(rh, bio));

	}
@@ -555,9 +555,9 @@ void dm_rh_dec(struct dm_region_hash *rh, region_t region) 
		 */



		/* do nothing for DM_RH_NOSYNC */

		if (unlikely(rh->barrier_failure)) {

		if (unlikely(rh->flush_failure)) {

			/*

			 * If a write barrier failed some time ago, we

			 * If a write flush failed some time ago, we

			 * don't know whether or not this write made it

			 * to the disk, so we must resync the device.

			 */