cifs: when a channel is not found for server, log its connection id

cifs_ses_get_chan_index gets the index for a given server pointer.
When a match is not found, we warn about a possible bug.
However, printing details about the non-matching server could be
more useful to debug here.
Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/sess.c

@@ -81,6 +81,9 @@ cifs_ses_get_chan_index(struct cifs_ses *ses,
 	}
 
 	/* If we didn't find the channel, it is likely a bug */
+	if (server)
+		cifs_dbg(VFS, "unable to get chan index for server: 0x%llx",
+			 server->conn_id);
 	WARN_ON(1);
 	return 0;
 }