cifs: force new session setup and tcon for dfs

BugLink: https://bugs.launchpad.net/bugs/1970977

Do not reuse existing sessions and tcons in DFS failover as it might
connect to different servers and shares.

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Cc: stable@vger.kernel.org
Reviewed-by: Enzo Matsumiya <ematsumiya@suse.de>
Signed-off-by: Steve French <stfrench@microsoft.com>
(cherry picked from commit fb39d30)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Philip Cox <philip.cox@canonical.com>
Acked-by: Joseph Salisbury <joseph.salisbury@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

Author: Paulo Alcantara

fs/cifs/connect.c

@@ -453,9 +453,7 @@ static int reconnect_target_unlocked(struct TCP_Server_Info *server, struct dfs_
 	return rc;
 }
 
-static int
-reconnect_dfs_server(struct TCP_Server_Info *server,
-		     bool mark_smb_session)
+static int reconnect_dfs_server(struct TCP_Server_Info *server)
 {
 	int rc = 0;
 	const char *refpath = server->current_fullpath + 1;
@@ -479,7 +477,12 @@ reconnect_dfs_server(struct TCP_Server_Info *server,
 	if (!cifs_tcp_ses_needs_reconnect(server, num_targets))
 		return 0;
 
-	cifs_mark_tcp_ses_conns_for_reconnect(server, mark_smb_session);
+	/*
+	 * Unconditionally mark all sessions & tcons for reconnect as we might be connecting to a
+	 * different server or share during failover.  It could be improved by adding some logic to
+	 * only do that in case it connects to a different server or share, though.
+	 */
+	cifs_mark_tcp_ses_conns_for_reconnect(server, true);
 
 	cifs_abort_connection(server);
 
@@ -537,7 +540,7 @@ int cifs_reconnect(struct TCP_Server_Info *server, bool mark_smb_session)
 	}
 	spin_unlock(&cifs_tcp_ses_lock);
 
-	return reconnect_dfs_server(server, mark_smb_session);
+	return reconnect_dfs_server(server);
 }
 #else
 int cifs_reconnect(struct TCP_Server_Info *server, bool mark_smb_session)