[PATCH v3 1/3] md-cluster: fix lock_comm leak and __sendmsg error path

[ghuicao]

From: Cao Guanghui <caoguanghui@xxxxxxxxxx>

Fix two error handling issues in cluster communication:

1. lock_comm() leaks MD_CLUSTER_SEND_LOCK if lock_token() fails.
   The bit is set by test_and_set_bit but never cleared on error,
   causing all subsequent cluster operations to hang permanently
   in wait_event().  Clear the bit before returning the error.

2. __sendmsg() has two problems in the failed_ack cleanup path:
   - ack_lockres is left in EX state if the down-conversion to CR
     fails, causing a cluster-wide deadlock.  Attempt to restore
     it to CR and log if that also fails.
   - The while loop for message_lockres unlock spins forever if
     a previous DLM operation timed out and left a pending request
     (dlm_unlock_sync returns -EBUSY immediately).  Change to a
     single attempt with error logging.

Fixes: 818da59f97d6 ("md-cluster: add the support for resize") (lock_comm)
Fixes: 601b515c5dcc ("Communication Framework: Sending functions") (__sendmsg)
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Cao Guanghui <caoguanghui@xxxxxxxxxx>
---
 drivers/md/md-cluster.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

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
@@ -735,6 +735,8 @@ static int lock_comm(struct md_cluster_info *cinfo, bool mddev_locked)
 	wait_event(cinfo->wait,
 		   !test_and_set_bit(MD_CLUSTER_SEND_LOCK, &cinfo->state));
 	rv = lock_token(cinfo);
+	if (rv)
+		clear_bit_unlock(MD_CLUSTER_SEND_LOCK, &cinfo->state);
 	if (set_bit)
 		clear_bit_unlock(MD_CLUSTER_HOLDING_MUTEX_FOR_RECVD, &cinfo->state);
 	return rv;
@@ -801,7 +803,15 @@ static int __sendmsg(struct md_cluster_info *cinfo, struct cluster_msg *cmsg)
 	}
 
 failed_ack:
-	while ((unlock_error = dlm_unlock_sync(cinfo->message_lockres)))
+	if (error) {
+		int ack_ret = dlm_lock_sync(cinfo->ack_lockres, DLM_LOCK_CR);
+
+		if (ack_ret)
+			pr_err("md-cluster: failed to restore ACK to CR (%d)\n",
+			       ack_ret);
+	}
+	unlock_error = dlm_unlock_sync(cinfo->message_lockres);
+	if (unlock_error)
 		pr_err("md-cluster: failed convert to NL on MESSAGE(%d)\n",
 			unlock_error);
 
-- 
2.34.1