[PATCH] dlm: don't warn when closing a node without a connection

[vienna-0FFH <viennaoffh@gmail.com>]

Opening and closing a configfs comm entry without ever configuring an
address for it triggers the following warning:

  mkdir /sys/kernel/config/dlm/cluster
  mkdir /sys/kernel/config/dlm/cluster/comms/1
  rmdir /sys/kernel/config/dlm/cluster/comms/1

  dlm: closing connection to node 1
  ------------[ cut here ]------------
  !con
  WARNING: fs/dlm/lowcomms.c:1455 at dlm_lowcomms_close+0x12d/0x470, CPU#1

Since commit 6f0b0b5d7ae7 ("fs: dlm: remove dlm_node_addrs lookup list")
the lowcomms connection has the same lifetime as the configfs comm
entry, but a connection is only created when an address is configured
via the addr attribute. Removing a comm entry for which no address was
ever set up is valid and the resulting close call has simply nothing
to do, so it must not warn.

Reported-by: syzbot+04dfbd15d442517e713a@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=04dfbd15d442517e713a
Fixes: 6f0b0b5d7ae7 ("fs: dlm: remove dlm_node_addrs lookup list")
Cc: stable@vger.kernel.org
Signed-off-by: vienna-0FFH <viennaoffh@gmail.com>
---
 fs/dlm/lowcomms.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
index 2aff1c7..86c7af9 100644
--- a/fs/dlm/lowcomms.c
+++ b/fs/dlm/lowcomms.c
@@ -1452,7 +1452,11 @@ int dlm_lowcomms_close(int nodeid)
 
 	idx = srcu_read_lock(&connections_srcu);
 	con = nodeid2con(nodeid, 0);
-	if (WARN_ON_ONCE(!con)) {
+	/* case of dlm_midcomms_close() for a node which never had an
+	 * address configured, so no connection was ever created and
+	 * there is nothing to close
+	 */
+	if (!con) {
 		srcu_read_unlock(&connections_srcu, idx);
 		return -ENOENT;
 	}
-- 
2.43.0