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author | 2021-07-03 11:31:26 +0200 | |
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committer | 2021-07-20 17:57:33 +0200 | |
commit | ed9eb71085ecb7ded9a5118cec2ab70667cc7350 (patch) | |
tree | dfd2877b2a298b43ef8415f8317a00f8e6dbb00f | |
parent | rbd: always kick acquire on "acquired" and "released" notifications (diff) | |
download | linux-ed9eb71085ecb7ded9a5118cec2ab70667cc7350.tar.gz linux-ed9eb71085ecb7ded9a5118cec2ab70667cc7350.tar.bz2 linux-ed9eb71085ecb7ded9a5118cec2ab70667cc7350.zip |
rbd: don't hold lock_rwsem while running_list is being drained
Currently rbd_quiesce_lock() holds lock_rwsem for read while blocking
on releasing_wait completion. On the I/O completion side, each image
request also needs to take lock_rwsem for read. Because rw_semaphore
implementation doesn't allow new readers after a writer has indicated
interest in the lock, this can result in a deadlock if something that
needs to take lock_rwsem for write gets involved. For example:
1. watch error occurs
2. rbd_watch_errcb() takes lock_rwsem for write, clears owner_cid and
releases lock_rwsem
3. after reestablishing the watch, rbd_reregister_watch() takes
lock_rwsem for write and calls rbd_reacquire_lock()
4. rbd_quiesce_lock() downgrades lock_rwsem to for read and blocks on
releasing_wait until running_list becomes empty
5. another watch error occurs
6. rbd_watch_errcb() blocks trying to take lock_rwsem for write
7. no in-flight image request can complete and delete itself from
running_list because lock_rwsem won't be granted anymore
A similar scenario can occur with "lock has been acquired" and "lock
has been released" notification handers which also take lock_rwsem for
write to update owner_cid.
We don't actually get anything useful from sitting on lock_rwsem in
rbd_quiesce_lock() -- owner_cid updates certainly don't need to be
synchronized with. In fact the whole owner_cid tracking logic could
probably be removed from the kernel client because we don't support
proxied maintenance operations.
Cc: stable@vger.kernel.org # 5.3+
URL: https://tracker.ceph.com/issues/42757
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Tested-by: Robin Geuze <robin.geuze@nl.team.blue>
-rw-r--r-- | drivers/block/rbd.c | 12 |
1 files changed, 5 insertions, 7 deletions
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index e77cea6a6189..784797fa9a53 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -4100,8 +4100,6 @@ again: static bool rbd_quiesce_lock(struct rbd_device *rbd_dev) { - bool need_wait; - dout("%s rbd_dev %p\n", __func__, rbd_dev); lockdep_assert_held_write(&rbd_dev->lock_rwsem); @@ -4113,11 +4111,11 @@ static bool rbd_quiesce_lock(struct rbd_device *rbd_dev) */ rbd_dev->lock_state = RBD_LOCK_STATE_RELEASING; rbd_assert(!completion_done(&rbd_dev->releasing_wait)); - need_wait = !list_empty(&rbd_dev->running_list); - downgrade_write(&rbd_dev->lock_rwsem); - if (need_wait) - wait_for_completion(&rbd_dev->releasing_wait); - up_read(&rbd_dev->lock_rwsem); + if (list_empty(&rbd_dev->running_list)) + return true; + + up_write(&rbd_dev->lock_rwsem); + wait_for_completion(&rbd_dev->releasing_wait); down_write(&rbd_dev->lock_rwsem); if (rbd_dev->lock_state != RBD_LOCK_STATE_RELEASING) |