dm: implement REQ_FLUSH/FUA support for bio-based dm
authorTejun Heo <tj@kernel.org>
Fri, 3 Sep 2010 09:56:19 +0000 (11:56 +0200)
committerJens Axboe <jaxboe@fusionio.com>
Fri, 10 Sep 2010 10:35:38 +0000 (12:35 +0200)
commitd87f4c14f27dc82d215108d8392a7d26687148a1
tree55f2a81f3df5d70fd85c4428089f6fe28540bcf4
parent3a2edd0d6ddbd5fa3b389ea6db811285415ce6c8
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: Tejun Heo <tj@kernel.org>
Cc: dm-devel@redhat.com
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
drivers/md/dm-crypt.c
drivers/md/dm-io.c
drivers/md/dm-log.c
drivers/md/dm-raid1.c
drivers/md/dm-region-hash.c
drivers/md/dm-snap-persistent.c
drivers/md/dm-snap.c
drivers/md/dm-stripe.c
drivers/md/dm.c