cifs: after disabling multichannel, mark tcon for reconnect

Once the server disables multichannel for an active multichannel
session, on the following reconnect, the client would reduce
the number of channels to 1. However, it could be the case that
the tree connect was active on one of these disabled channels.
This results in an unrecoverable state.

This change fixes that by making sure that whenever a channel
is being terminated, the session and tcon are marked for
reconnect too. This could mean a few redundant tree connect
calls to the server, but considering that this is not a frequent
event, we should be okay.

Fixes: ee1d217 ("cifs: handle when server stops supporting multichannel")
Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: sprasad-microsoft

fs/smb/client/connect.c

@@ -216,17 +216,21 @@ cifs_mark_tcp_ses_conns_for_reconnect(struct TCP_Server_Info *server,
 	/* If server is a channel, select the primary channel */
 	pserver = SERVER_IS_CHAN(server) ? server->primary_server : server;
 
+	/*
+	 * if the server has been marked for termination, there is a
+	 * chance that the remaining channels all need reconnect. To be
+	 * on the safer side, mark the session and trees for reconnect
+	 * for this scenario. This might cause a few redundant session
+	 * setup and tree connect requests, but it is better than not doing
+	 * a tree connect when needed, and all following requests failing
+	 */
+	if (server->terminate) {
+		mark_smb_session = true;
+		server = pserver;
+	}
 
 	spin_lock(&cifs_tcp_ses_lock);
 	list_for_each_entry_safe(ses, nses, &pserver->smb_ses_list, smb_ses_list) {
-		/*
-		 * if channel has been marked for termination, nothing to do
-		 * for the channel. in fact, we cannot find the channel for the
-		 * server. So safe to exit here
-		 */
-		if (server->terminate)
-			break;
-
 		/* check if iface is still active */
 		if (!cifs_chan_is_iface_active(ses, server))
 			cifs_chan_update_iface(ses, server);