Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client
Pull Ceph fixes from Sage Weil:
"These paches from Ilya finally squash a race condition with layered
images that he's been chasing for a while"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client:
rbd: drop parent_ref in rbd_dev_unprobe() unconditionally
rbd: fix rbd_dev_parent_get() when parent_overlap == 0
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 3ec85df..8a86b62 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -2098,32 +2098,26 @@
* 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.
*/
static bool rbd_dev_parent_get(struct rbd_device *rbd_dev)
{
- int counter;
+ int counter = 0;
if (!rbd_dev->parent_spec)
return false;
- counter = atomic_inc_return_safe(&rbd_dev->parent_ref);
- if (counter > 0 && rbd_dev->parent_overlap)
- return true;
-
- /* Image was flattened, but parent is not yet torn down */
+ down_read(&rbd_dev->header_rwsem);
+ if (rbd_dev->parent_overlap)
+ counter = atomic_inc_return_safe(&rbd_dev->parent_ref);
+ up_read(&rbd_dev->header_rwsem);
if (counter < 0)
rbd_warn(rbd_dev, "parent reference overflow");
- return false;
+ return counter > 0;
}
/*
@@ -4239,7 +4233,6 @@
*/
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);
@@ -4285,7 +4278,6 @@
* treat it specially.
*/
rbd_dev->parent_overlap = overlap;
- smp_mb();
if (!overlap) {
/* A null parent_spec indicates it's the initial probe */
@@ -5114,10 +5106,7 @@
{
struct rbd_image_header *header;
- /* Drop parent reference unless it's already been done (or none) */
-
- if (rbd_dev->parent_overlap)
- rbd_dev_parent_put(rbd_dev);
+ rbd_dev_parent_put(rbd_dev);
/* Free dynamic fields from the header, then zero it out */