dm space map disk: fix some book keeping in the disk space map

When decrementing the reference count for a block, the free count wasn't
being updated if the reference count went to zero.

Cc: stable@vger.kernel.org
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/drivers/md/persistent-data/dm-space-map-disk.c b/drivers/md/persistent-data/dm-space-map-disk.c
index ebb280a14325..32adf6b4a9c7 100644
--- a/drivers/md/persistent-data/dm-space-map-disk.c
+++ b/drivers/md/persistent-data/dm-space-map-disk.c
@@ -142,10 +142,23 @@ static int sm_disk_inc_block(struct dm_space_map *sm, dm_block_t b)
 
 static int sm_disk_dec_block(struct dm_space_map *sm, dm_block_t b)
 {
+        int r;
+        uint32_t old_count;
         enum allocation_event ev;
         struct sm_disk *smd = container_of(sm, struct sm_disk, sm);
 
-        return sm_ll_dec(&smd->ll, b, &ev);
+        r = sm_ll_dec(&smd->ll, b, &ev);
+        if (!r && (ev == SM_FREE)) {
+                /*
+                 * It's only free if it's also free in the last
+                 * transaction.
+                 */
+                r = sm_ll_lookup(&smd->old_ll, b, &old_count);
+                if (!r && !old_count)
+                        smd->nr_allocated_this_transaction--;
+        }
+
+        return r;
 }
 
 static int sm_disk_new_block(struct dm_space_map *sm, dm_block_t *b)