dm raid1: support flush

Flush support for dm-raid1.

When it receives an empty barrier, submit it to all the devices via dm-io.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 23 insertions, 2 deletions

diff --git a/drivers/md/dm-region-hash.c b/drivers/md/dm-region-hash.c
index 36dbe29f2fd6..00806b760ccd 100644
--- a/drivers/md/dm-region-hash.c
+++ b/drivers/md/dm-region-hash.c
@@ -79,6 +79,11 @@ struct dm_region_hash {
         struct list_head recovered_regions;
         struct list_head failed_recovered_regions;
 
+        /*
+         * If there was a barrier failure no regions can be marked clean.
+         */
+        int barrier_failure;
+
         void *context;
         sector_t target_begin;
 
@@ -211,6 +216,7 @@ 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->region_pool = mempool_create_kmalloc_pool(MIN_REGIONS,
                                                       sizeof(struct dm_region));
@@ -395,6 +401,11 @@ void dm_rh_mark_nosync(struct dm_region_hash *rh,
         region_t region = dm_rh_bio_to_region(rh, bio);
         int recovering = 0;
 
+        if (bio_empty_barrier(bio)) {
+                rh->barrier_failure = 1;
+                return;
+        }
+
         /* We must inform the log that the sync count has changed. */
         log->type->set_region_sync(log, region, 0);
 
@@ -515,8 +526,11 @@ 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)
+        for (bio = bios->head; bio; bio = bio->bi_next) {
+                if (bio_empty_barrier(bio))
+                        continue;
                 rh_inc(rh, dm_rh_bio_to_region(rh, bio));
+        }
 }
 EXPORT_SYMBOL_GPL(dm_rh_inc_pending);
 
@@ -544,7 +558,14 @@ void dm_rh_dec(struct dm_region_hash *rh, region_t region)
                  */
 
                 /* do nothing for DM_RH_NOSYNC */
-                if (reg->state == DM_RH_RECOVERING) {
+                if (unlikely(rh->barrier_failure)) {
+                        /*
+                         * If a write barrier failed some time ago, we
+                         * don't know whether or not this write made it
+                         * to the disk, so we must resync the device.
+                         */
+                        reg->state = DM_RH_NOSYNC;
+                } else if (reg->state == DM_RH_RECOVERING) {
                         list_add_tail(&reg->list, &rh->quiesced_regions);
                 } else if (reg->state == DM_RH_DIRTY) {
                         reg->state = DM_RH_CLEAN;