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authorAlex Elder <elder@inktank.com>2013-05-06 17:40:33 -0500
committerAlex Elder <elder@inktank.com>2013-05-13 15:06:45 -0500
commit392a9dad7e777296fe79d97a6b3acd735ad2eb5f (patch)
tree3007be625c9d59c38184bce538c20bf233441b06
parenta2acd00e7964dbb1668a5956c9d0a4bdeb838c4a (diff)
rbd: detect when clone image is flattened
A format 2 clone image can be the subject of a "flatten" operation, during which all of its data gets "copied up" from its parent image, leaving the image fully populated. Once this is complete, the clone's association with the parent is abolished. Since this can occur when a clone is mapped, we need to detect when it has occurred and handle it accordingly. We know an image has been flattened when we know it at one time had a parent, but we have learned (via a "get_parent" object class method call) it no longer has one. There might be in-flight requests at the point we learn an image has been flattened, so we can't simply clean up parent data structures right away. Instead, we'll drop the initial parent reference when the parent has disappeared (rather than when the image gets destroyed), which will allow the last in-flight reference to clean things up when it's complete. We leverage the fact that a zero parent overlap renders an image effectively unlayered. We set the overlap to 0 at the point we detect the clone image has flattened, which allows the unlayered behavior to take effect immediately, while keeping other parent structures in place until in-flight requests to complete. This and the next few patches resolve: http://tracker.ceph.com/issues/3763 Signed-off-by: Alex Elder <elder@inktank.com> Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
-rw-r--r--drivers/block/rbd.c30
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 */