2 files changed, 17 insertions, 1 deletions

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 746603b42f86..6c96db26b87c 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -370,6 +370,7 @@ static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snaps
         struct dm_snap_pending_exception *pe = mempool_alloc(s->pending_pool,
                                                              GFP_NOIO);
 
+        atomic_inc(&s->pending_exceptions_count);
         pe->snap = s;
 
         return pe;
@@ -377,7 +378,11 @@ static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snaps
 
 static void free_pending_exception(struct dm_snap_pending_exception *pe)
 {
-        mempool_free(pe, pe->snap->pending_pool);
+        struct dm_snapshot *s = pe->snap;
+
+        mempool_free(pe, s->pending_pool);
+        smp_mb__before_atomic_dec();
+        atomic_dec(&s->pending_exceptions_count);
 }
 
 static void insert_completed_exception(struct dm_snapshot *s,
@@ -602,6 +607,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 
         s->valid = 1;
         s->active = 0;
+        atomic_set(&s->pending_exceptions_count, 0);
         init_rwsem(&s->lock);
         spin_lock_init(&s->pe_lock);
         s->ti = ti;
@@ -728,6 +734,14 @@ static void snapshot_dtr(struct dm_target *ti)
         /* After this returns there can be no new kcopyd jobs. */
         unregister_snapshot(s);
 
+        while (atomic_read(&s->pending_exceptions_count))
+                yield();
+        /*
+         * Ensure instructions in mempool_destroy aren't reordered
+         * before atomic_read.
+         */
+        smp_mb();
+
 #ifdef CONFIG_DM_DEBUG
         for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
                 BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
diff --git a/drivers/md/dm-snap.h b/drivers/md/dm-snap.h
index f07315fe2362..99c0106ede2d 100644
--- a/drivers/md/dm-snap.h
+++ b/drivers/md/dm-snap.h
@@ -160,6 +160,8 @@ struct dm_snapshot {
 
         mempool_t *pending_pool;
 
+        atomic_t pending_exceptions_count;
+
         struct exception_table pending;
         struct exception_table complete;