dm space map metadata: fix occasional leak of a metadata block on resize

The metadata space map has a simplified 'bootstrap' mode that is
operational when extending the space maps.  Whilst in this mode it's
possible for some refcount decrement operations to become queued (eg, as
a result of shadowing one of the bitmap indexes).  These decrements were
not being applied when switching out of bootstrap mode.

The effect of this bug was the leaking of a 4k metadata block.  This is
detected by the latest version of thin_check as a non fatal error.

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

1 files changed, 35 insertions, 15 deletions

diff --git a/drivers/md/persistent-data/dm-space-map-metadata.c b/drivers/md/persistent-data/dm-space-map-metadata.c
index e8a904298887..53091295fce9 100644
--- a/drivers/md/persistent-data/dm-space-map-metadata.c
+++ b/drivers/md/persistent-data/dm-space-map-metadata.c
@@ -204,6 +204,27 @@ static void in(struct sm_metadata *smm)
         smm->recursion_count++;
 }
 
+static int apply_bops(struct sm_metadata *smm)
+{
+        int r = 0;
+
+        while (!brb_empty(&smm->uncommitted)) {
+                struct block_op bop;
+
+                r = brb_pop(&smm->uncommitted, &bop);
+                if (r) {
+                        DMERR("bug in bop ring buffer");
+                        break;
+                }
+
+                r = commit_bop(smm, &bop);
+                if (r)
+                        break;
+        }
+
+        return r;
+}
+
 static int out(struct sm_metadata *smm)
 {
         int r = 0;
@@ -216,21 +237,8 @@ static int out(struct sm_metadata *smm)
                 return -ENOMEM;
         }
 
-        if (smm->recursion_count == 1) {
-                while (!brb_empty(&smm->uncommitted)) {
-                        struct block_op bop;
-
-                        r = brb_pop(&smm->uncommitted, &bop);
-                        if (r) {
-                                DMERR("bug in bop ring buffer");
-                                break;
-                        }
-
-                        r = commit_bop(smm, &bop);
-                        if (r)
-                                break;
-                }
-        }
+        if (smm->recursion_count == 1)
+                apply_bops(smm);
 
         smm->recursion_count--;
 
@@ -704,6 +712,12 @@ static int sm_metadata_extend(struct dm_space_map *sm, dm_block_t extra_blocks)
                 }
                 old_len = smm->begin;
 
+                r = apply_bops(smm);
+                if (r) {
+                        DMERR("%s: apply_bops failed", __func__);
+                        goto out;
+                }
+
                 r = sm_ll_commit(&smm->ll);
                 if (r)
                         goto out;
@@ -773,6 +787,12 @@ int dm_sm_metadata_create(struct dm_space_map *sm,
         if (r)
                 return r;
 
+        r = apply_bops(smm);
+        if (r) {
+                DMERR("%s: apply_bops failed", __func__);
+                return r;
+        }
+
         return sm_metadata_commit(sm);
 }