rbd: don't assume RBD_LOCK_STATE_LOCKED for exclusive mappings

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From: Ilya Dryomov <idryomov@xxxxxxxxx>

commit 2237ceb71f89837ac47c5dce2aaa2c2b3a337a3c upstream.

Every time a watch is reestablished after getting lost, we need to
update the cookie which involves quiescing exclusive lock.  For this,
we transition from RBD_LOCK_STATE_LOCKED to RBD_LOCK_STATE_QUIESCING
roughly for the duration of rbd_reacquire_lock() call.  If the mapping
is exclusive and I/O happens to arrive in this time window, it's failed
with EROFS (later translated to EIO) based on the wrong assumption in
rbd_img_exclusive_lock() -- "lock got released?" check there stopped
making sense with commit a2b1da09793d ("rbd: lock should be quiesced on
reacquire").

To make it worse, any such I/O is added to the acquiring list before
EROFS is returned and this sets up for violating rbd_lock_del_request()
precondition that the request is either on the running list or not on
any list at all -- see commit ded080c86b3f ("rbd: don't move requests
to the running list on errors").  rbd_lock_del_request() ends up
processing these requests as if they were on the running list which
screws up quiescing_wait completion counter and ultimately leads to

    rbd_assert(!completion_done(&rbd_dev->quiescing_wait));

being triggered on the next watch error.

Cc: stable@xxxxxxxxxxxxxxx # 06ef84c4e9c4: rbd: rename RBD_LOCK_STATE_RELEASING and releasing_wait
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 637cd060537d ("rbd: new exclusive lock wait/wake code")
Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx>
Reviewed-by: Dongsheng Yang <dongsheng.yang@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/block/rbd.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -3608,6 +3608,7 @@ static void rbd_lock_del_request(struct
 	lockdep_assert_held(&rbd_dev->lock_rwsem);
 	spin_lock(&rbd_dev->lock_lists_lock);
 	if (!list_empty(&img_req->lock_item)) {
+		rbd_assert(!list_empty(&rbd_dev->running_list));
 		list_del_init(&img_req->lock_item);
 		need_wakeup = (rbd_dev->lock_state == RBD_LOCK_STATE_QUIESCING &&
 			       list_empty(&rbd_dev->running_list));
@@ -3627,11 +3628,6 @@ static int rbd_img_exclusive_lock(struct
 	if (rbd_lock_add_request(img_req))
 		return 1;
 
-	if (rbd_dev->opts->exclusive) {
-		WARN_ON(1); /* lock got released? */
-		return -EROFS;
-	}
-
 	/*
 	 * Note the use of mod_delayed_work() in rbd_acquire_lock()
 	 * and cancel_delayed_work() in wake_lock_waiters().
@@ -4701,6 +4697,10 @@ static void rbd_reacquire_lock(struct rb
 			rbd_warn(rbd_dev, "failed to update lock cookie: %d",
 				 ret);
 
+		if (rbd_dev->opts->exclusive)
+			rbd_warn(rbd_dev,
+			     "temporarily releasing lock on exclusive mapping");
+
 		/*
 		 * Lock cookie cannot be updated on older OSDs, so do
 		 * a manual release and queue an acquire.


Patches currently in stable-queue which might be from idryomov@xxxxxxxxx are

queue-5.4/rbd-don-t-assume-rbd_lock_state_locked-for-exclusive-mappings.patch
queue-5.4/rbd-rename-rbd_lock_state_releasing-and-releasing_wait.patch
queue-5.4/rbd-don-t-assume-rbd_is_lock_owner-for-exclusive-mappings.patch




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