1 files changed, 28 insertions, 9 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index fd9656b5fdb9..8c90a39c2a91 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -264,7 +264,7 @@ struct rbd_device {
         spinlock_t              lock;           /* queue lock */
 
         struct rbd_image_header header;
-        atomic_t                exists;
+        unsigned long           flags;
         struct rbd_spec         *spec;
 
         char                    *header_name;
@@ -292,6 +292,12 @@ struct rbd_device {
         unsigned long           open_count;
 };
 
+/* Flag bits for rbd_dev->flags */
+
+enum rbd_dev_flags {
+        RBD_DEV_FLAG_EXISTS,    /* mapped snapshot has not been deleted */
+};
+
 static DEFINE_MUTEX(ctl_mutex);   /* Serialize open/close/setup/teardown */
 
 static LIST_HEAD(rbd_dev_list);    /* devices */
@@ -782,7 +788,8 @@ static int rbd_dev_set_mapping(struct rbd_device *rbd_dev)
                         goto done;
                 rbd_dev->mapping.read_only = true;
         }
-        atomic_set(&rbd_dev->exists, 1);
+        set_bit(RBD_DEV_FLAG_EXISTS, &rbd_dev->flags);
+
 done:
         return ret;
 }
@@ -1877,9 +1884,14 @@ static void rbd_request_fn(struct request_queue *q)
                         rbd_assert(rbd_dev->spec->snap_id == CEPH_NOSNAP);
                 }
 
-                /* Quit early if the snapshot has disappeared */
-
-                if (!atomic_read(&rbd_dev->exists)) {
+                /*
+                 * Quit early if the mapped snapshot no longer
+                 * exists.  It's still possible the snapshot will
+                 * have disappeared by the time our request arrives
+                 * at the osd, but there's no sense in sending it if
+                 * we already know.
+                 */
+                if (!test_bit(RBD_DEV_FLAG_EXISTS, &rbd_dev->flags)) {
                         dout("request for non-existent snapshot");
                         rbd_assert(rbd_dev->spec->snap_id != CEPH_NOSNAP);
                         result = -ENXIO;
@@ -2571,7 +2583,7 @@ struct rbd_device *rbd_dev_create(struct rbd_client *rbdc,
                 return NULL;
 
         spin_lock_init(&rbd_dev->lock);
-        atomic_set(&rbd_dev->exists, 0);
+        rbd_dev->flags = 0;
         INIT_LIST_HEAD(&rbd_dev->node);
         INIT_LIST_HEAD(&rbd_dev->snaps);
         init_rwsem(&rbd_dev->header_rwsem);
@@ -3200,10 +3212,17 @@ static int rbd_dev_snaps_update(struct rbd_device *rbd_dev)
                 if (snap_id == CEPH_NOSNAP || (snap && snap->id > snap_id)) {
                         struct list_head *next = links->next;
 
-                        /* Existing snapshot not in the new snap context */
-
+                        /*
+                         * A previously-existing snapshot is not in
+                         * the new snap context.
+                         *
+                         * If the now missing snapshot is the one the
+                         * image is mapped to, clear its exists flag
+                         * so we can avoid sending any more requests
+                         * to it.
+                         */
                         if (rbd_dev->spec->snap_id == snap->id)
-                                atomic_set(&rbd_dev->exists, 0);
+                                clear_bit(RBD_DEV_FLAG_EXISTS, &rbd_dev->flags);
                         rbd_remove_snap_dev(snap);
                         dout("%ssnap id %llu has been removed\n",
                                 rbd_dev->spec->snap_id == snap->id ?