cifs: add WARN_ON for when chan_count goes below minimum

chan_count keeps track of the total number of channels.
Since at least the primary channel will always be connected,
this value can never go below 1. Warn if that happens.
Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/sess.c

@@ -347,6 +347,11 @@ cifs_ses_add_channel(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses,
 		/* we rely on all bits beyond chan_count to be clear */
 		cifs_chan_clear_need_reconnect(ses, chan->server);
 		ses->chan_count--;
+		/*
+		 * chan_count should never reach 0 as at least the primary
+		 * channel is always allocated
+		 */
+		WARN_ON(ses->chan_count < 1);
 		spin_unlock(&ses->chan_lock);
 	}