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 @@ -4248,15 +4248,11 @@ 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); @@ -4281,14 +4277,12 @@ 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);