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, 8 insertions, 8 deletions

diff --git a/drivers/md/dm-region-hash.c b/drivers/md/dm-region-hash.c
index bd5c58b28868..dad011aed0c9 100644
--- a/drivers/md/dm-region-hash.c
+++ b/drivers/md/dm-region-hash.c
@@ -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.
                          */