[Ocfs2-devel] [PATCH] ocfs2/dlm: fix race between convert and recovery

[Joseph Qi <joseph.qi@huawei.com>]

There is a race window between dlmconvert_remote and
dlm_move_lockres_to_recovery_list, which will cause a lock with
OCFS2_LOCK_BUSY in grant list, thus system hangs.

dlmconvert_remote
{
	spin_lock(&res->spinlock);
	list_move_tail(&lock->list, &res->converting);
	lock->convert_pending = 1;
	spin_unlock(&res->spinlock);

	status = dlm_send_remote_convert_request();
	>>>>>> race window, master has queued ast and return DLM_NORMAL,
	       and then down before sending ast.
	       this node detects master down and call
	       dlm_move_lockres_to_recovery_list, which will revert the
	       lock to grant list.
	       Then OCFS2_LOCK_BUSY won't be cleared as new master won't
	       send ast any more because it thinks already be authorized.

	spin_lock(&res->spinlock);
	lock->convert_pending = 0;
	if (status != DLM_NORMAL)
		dlm_revert_pending_convert(res, lock);
	spin_unlock(&res->spinlock);
}

In this case, just leave it in convert list and new master will take
care of it after recovery. And if convert request returns other than
DLM_NORMAL, convert thread will do the revert itself.
So remove the revert logic in dlm_move_lockres_to_recovery_list.

Reported-by: Yiwen Jiang <jiangyiwen@huawei.com>
Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
Cc: <stable@vger.kernel.org>
---
 fs/ocfs2/dlm/dlmrecovery.c | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/fs/ocfs2/dlm/dlmrecovery.c b/fs/ocfs2/dlm/dlmrecovery.c
index ce12e0b..d797d49 100644
--- a/fs/ocfs2/dlm/dlmrecovery.c
+++ b/fs/ocfs2/dlm/dlmrecovery.c
@@ -2058,15 +2058,7 @@ void dlm_move_lockres_to_recovery_list(struct dlm_ctxt *dlm,
 		queue = dlm_list_idx_to_ptr(res, i);
 		list_for_each_entry_safe(lock, next, queue, list) {
 			dlm_lock_get(lock);
-			if (lock->convert_pending) {
-				/* move converting lock back to granted */
-				BUG_ON(i != DLM_CONVERTING_LIST);
-				mlog(0, "node died with convert pending "
-				     "on %.*s. move back to granted list.\n",
-				     res->lockname.len, res->lockname.name);
-				dlm_revert_pending_convert(res, lock);
-				lock->convert_pending = 0;
-			} else if (lock->lock_pending) {
+			if (lock->lock_pending) {
 				/* remove pending lock requests completely */
 				BUG_ON(i != DLM_BLOCKED_LIST);
 				mlog(0, "node died with lock pending "
-- 
1.8.4.3