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>

1 files changed, 4 insertions, 4 deletions

diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index 7c081bcbc3cf..19a59b041c27 100644
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -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;
         }