cifs: fix potential race with cifsd thread

To avoid racing with demultiplex thread while it is handling data on
socket, use cifs_signal_cifsd_for_reconnect() helper for marking
current server to reconnect and let the demultiplex thread handle the
rest.

Fixes: dca6581 ("cifs: use a different reconnect helper for non-cifsd threads")
Reviewed-by: Enzo Matsumiya <ematsumiya@suse.de>
Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: Paulo Alcantara

fs/cifs/connect.c

@@ -4465,7 +4465,7 @@ static int tree_connect_dfs_target(const unsigned int xid, struct cifs_tcon *tco
 	 */
 	if (rc && server->current_fullpath != server->origin_fullpath) {
 		server->current_fullpath = server->origin_fullpath;
-		cifs_reconnect(tcon->ses->server, true);
+		cifs_signal_cifsd_for_reconnect(server, true);
 	}
 
 	dfs_cache_free_tgts(tl);

fs/cifs/netmisc.c

@@ -896,7 +896,7 @@ map_and_check_smb_error(struct mid_q_entry *mid, bool logErr)
 		if (class == ERRSRV && code == ERRbaduid) {
 			cifs_dbg(FYI, "Server returned 0x%x, reconnecting session...\n",
 				code);
-			cifs_reconnect(mid->server, false);
+			cifs_signal_cifsd_for_reconnect(mid->server, false);
 		}
 	}