[PATCH v2 3/3] md-cluster: fix ack_lockres leak in __sendmsg error path

[ghuicao]

From: Cao Guanghui <caoguanghui@xxxxxxxxxx>

In __sendmsg(), if the down-conversion of ack_lockres from EX to CR
fails (step 5), the code jumps to failed_ack which only unlocks
message_lockres.  The ack_lockres is left in EX state, causing a
cluster-wide deadlock as other nodes cannot acquire the ack lock.

Restore ack_lockres to CR in the failed_ack path when an error occurred,
so the lock is not leaked in EX state.

Fixes: 601b515c5dcc ("Communication Framework: Sending functions")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Cao Guanghui <caoguanghui@xxxxxxxxxx>
---
 drivers/md/md-cluster.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/md/md-cluster.c b/drivers/md/md-cluster.c
--- a/drivers/md/md-cluster.c
+++ b/drivers/md/md-cluster.c
@@ -801,8 +801,10 @@ static int __sendmsg(struct md_cluster_info *cinfo, struct cluster_msg *cmsg)
 	}
 
 failed_ack:
+	if (error)
+		dlm_lock_sync(cinfo->ack_lockres, DLM_LOCK_CR);
 	while ((unlock_error = dlm_unlock_sync(cinfo->message_lockres)))
 		pr_err("md-cluster: failed convert to NL on MESSAGE(%d)\n",
 			unlock_error);
 
 	return error;
-- 
2.34.1