cifs: Introduce helpers for finding TCP connection

Add helpers for finding TCP connections that are good candidates for
being used by DFS refresh worker.
Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/dfs_cache.c

@@ -1305,6 +1305,30 @@ static char *get_dfs_root(const char *path)
 	return npath;
 }
 
+static inline void put_tcp_server(struct TCP_Server_Info *server)
+{
+	cifs_put_tcp_session(server, 0);
+}
+
+static struct TCP_Server_Info *get_tcp_server(struct smb_vol *vol)
+{
+	struct TCP_Server_Info *server;
+
+	server = cifs_find_tcp_session(vol);
+	if (IS_ERR_OR_NULL(server))
+		return NULL;
+
+	spin_lock(&GlobalMid_Lock);
+	if (server->tcpStatus != CifsGood) {
+		spin_unlock(&GlobalMid_Lock);
+		put_tcp_server(server);
+		return NULL;
+	}
+	spin_unlock(&GlobalMid_Lock);
+
+	return server;
+}
+
 /* Find root SMB session out of a DFS link path */
 static struct cifs_ses *find_root_ses(struct vol_info *vi,
 				      struct cifs_tcon *tcon,
@@ -1347,13 +1371,8 @@ static struct cifs_ses *find_root_ses(struct vol_info *vi,
 		goto out;
 	}
 
-	server = cifs_find_tcp_session(&vol);
-	if (IS_ERR_OR_NULL(server)) {
-		ses = ERR_PTR(-EHOSTDOWN);
-		goto out;
-	}
-	if (server->tcpStatus != CifsGood) {
-		cifs_put_tcp_session(server, 0);
+	server = get_tcp_server(&vol);
+	if (!server) {
 		ses = ERR_PTR(-EHOSTDOWN);
 		goto out;
 	}
@@ -1451,19 +1470,18 @@ static void refresh_cache_worker(struct work_struct *work)
 	mutex_lock(&vol_lock);
 
 	list_for_each_entry(vi, &vol_list, list) {
-		server = cifs_find_tcp_session(&vi->smb_vol);
-		if (IS_ERR_OR_NULL(server))
+		server = get_tcp_server(&vi->smb_vol);
+		if (!server)
 			continue;
-		if (server->tcpStatus != CifsGood)
-			goto next;
+
 		get_tcons(server, &list);
 		list_for_each_entry_safe(tcon, ntcon, &list, ulist) {
 			refresh_tcon(vi, tcon);
 			list_del_init(&tcon->ulist);
 			cifs_put_tcon(tcon);
 		}
-next:
-		cifs_put_tcp_session(server, 0);
+
+		put_tcp_server(server);
 	}
 	queue_delayed_work(dfscache_wq, &refresh_task, cache_ttl * HZ);
 	mutex_unlock(&vol_lock);