rbd: detect when clone image is flattened

[~andy/linux] / drivers / block / rbd.c

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 8b6091b6d5cbb4f007b06cd964ffd3e7a12ac203..9717e20f34776aa509b343bca250125a997fb421 100644 (file)
--- 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 */