[PATCH 5.4 098/108] rbd: always kick acquire on "acquired" and "released" notifications

Greg Kroah-Hartman
2021-07-26T16:15:36Z

From: Ilya Dryomov <idryomov@gmail.com>

commit 8798d070d416d18a75770fc19787e96705073f43 upstream.

Skipping the "lock has been released" notification if the lock owner
is not what we expect based on owner_cid can lead to I/O hangs.
One example is our own notifications: because owner_cid is cleared
in rbd_unlock(), when we get our own notification it is processed as
unexpected/duplicate and maybe_kick_acquire() isn't called. If a peer
that requested the lock then doesn't go through with acquiring it,
I/O requests that came in while the lock was being quiesced would
be stalled until another I/O request is submitted and kicks acquire
from rbd_img_exclusive_lock().

This makes the comment in rbd_release_lock() actually true: prior to
this change the canceled work was being requeued in response to the
"lock has been acquired" notification from rbd_handle_acquired_lock().

Cc: stable@vger.kernel.org # 5.3+
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Tested-by: Robin Geuze <robin.geuze@nl.team.blue>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/block/rbd.c | 20 +++++++-------------
1 file changed, 7 insertions(+), 13 deletions(-)

--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -4340,15 +4340,11 @@ static void rbd_handle_acquired_lock(str
if (!rbd_cid_equal(&cid, &rbd_empty_cid)) {
down_write(&rbd_dev->lock_rwsem);
if (rbd_cid_equal(&cid, &rbd_dev->owner_cid)) {
- /*
- * we already know that the remote client is
- * the owner
- */
- up_write(&rbd_dev->lock_rwsem);
- return;
+ dout("%s rbd_dev %p cid %llu-%llu == owner_cid\n",
+ __func__, rbd_dev, cid.gid, cid.handle);
+ } else {
+ rbd_set_owner_cid(rbd_dev, &cid);
}
-
- rbd_set_owner_cid(rbd_dev, &cid);
downgrade_write(&rbd_dev->lock_rwsem);
} else {
down_read(&rbd_dev->lock_rwsem);
@@ -4373,14 +4369,12 @@ static void rbd_handle_released_lock(str
if (!rbd_cid_equal(&cid, &rbd_empty_cid)) {
down_write(&rbd_dev->lock_rwsem);
if (!rbd_cid_equal(&cid, &rbd_dev->owner_cid)) {
- dout("%s rbd_dev %p unexpected owner, cid %llu-%llu != owner_cid %llu-%llu\n",
+ dout("%s rbd_dev %p cid %llu-%llu != owner_cid %llu-%llu\n",
__func__, rbd_dev, cid.gid, cid.handle,
rbd_dev->owner_cid.gid, rbd_dev->owner_cid.handle);
- up_write(&rbd_dev->lock_rwsem);
- return;
+ } else {
+ rbd_set_owner_cid(rbd_dev, &rbd_empty_cid);
}
-
- rbd_set_owner_cid(rbd_dev, &rbd_empty_cid);
downgrade_write(&rbd_dev->lock_rwsem);
} else {
down_read(&rbd_dev->lock_rwsem);