1 files changed, 28 insertions, 2 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 8b6091b6d5cb..9717e20f3477 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -1929,6 +1929,11 @@ static void rbd_dev_parent_put(struct rbd_device *rbd_dev)
  * If an image has a non-zero parent overlap, get a reference to its
  * parent.
  *
+ * We must get the reference before checking for the overlap to
+ * coordinate properly with zeroing the parent overlap in
+ * rbd_dev_v2_parent_info() when an image gets flattened.  We
+ * drop it again if there is no overlap.
+ *
  * Returns true if the rbd device has a parent with a non-zero
  * overlap and a reference for it was successfully taken, or
  * false otherwise.
@@ -3782,8 +3787,26 @@ static int rbd_dev_v2_parent_info(struct rbd_device *rbd_dev)
         end = reply_buf + ret;
         ret = -ERANGE;
         ceph_decode_64_safe(&p, end, pool_id, out_err);
-        if (pool_id == CEPH_NOPOOL)
+        if (pool_id == CEPH_NOPOOL) {
+                /*
+                 * Either the parent never existed, or we have
+                 * record of it but the image got flattened so it no
+                 * longer has a parent.  When the parent of a
+                 * layered image disappears we immediately set the
+                 * overlap to 0.  The effect of this is that all new
+                 * requests will be treated as if the image had no
+                 * parent.
+                 */
+                if (rbd_dev->parent_overlap) {
+                        rbd_dev->parent_overlap = 0;
+                        smp_mb();
+                        rbd_dev_parent_put(rbd_dev);
+                        pr_info("%s: clone image has been flattened\n",
+                                rbd_dev->disk->disk_name);
+                }
+
                 goto out;       /* No parent?  No problem. */
+        }
 
         /* The ceph file layout needs to fit pool id in 32 bits */
 
@@ -4633,7 +4656,10 @@ static void rbd_dev_unprobe(struct rbd_device *rbd_dev)
 {
         struct rbd_image_header *header;
 
-        rbd_dev_parent_put(rbd_dev);
+        /* Drop parent reference unless it's already been done (or none) */
+
+        if (rbd_dev->parent_overlap)
+                rbd_dev_parent_put(rbd_dev);
 
         /* Free dynamic fields from the header, then zero it out */