smb: client: get rid of TCP_Server_Info::refpath_lock

TCP_Server_Info::leaf_fullpath is allocated in cifs_get_tcp_session()
and never changed afterwards, so there is no need to serialize its
access.

Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: Paulo Alcantara

fs/smb/client/cifsglob.h

@@ -811,18 +811,9 @@ struct TCP_Server_Info {
 	bool use_swn_dstaddr;
 	struct sockaddr_storage swn_dstaddr;
 #endif
-	struct mutex refpath_lock; /* protects leaf_fullpath */
 	/*
-	 * leaf_fullpath: Canonical DFS referral path related to this
-	 *                connection.
-	 *                It is used in DFS cache refresher, reconnect and may
-	 *                change due to nested DFS links.
-	 *
-	 * Protected by @refpath_lock and @srv_lock.  The @refpath_lock is
-	 * mostly used for not requiring a copy of @leaf_fullpath when getting
-	 * cached or new DFS referrals (which might also sleep during I/O).
-	 * While @srv_lock is held for making string and NULL comparisons against
-	 * both fields as in mount(2) and cache refresh.
+	 * Canonical DFS referral path used in cifs_reconnect() for failover as
+	 * well as in DFS cache refresher.
 	 *
 	 * format: \\HOST\SHARE[\OPTIONAL PATH]
 	 */

fs/smb/client/connect.c

@@ -492,7 +492,7 @@ static int reconnect_target_locked(struct TCP_Server_Info *server,
 static int reconnect_dfs_server(struct TCP_Server_Info *server)
 {
 	struct dfs_cache_tgt_iterator *target_hint = NULL;
-
+	const char *ref_path = server->leaf_fullpath + 1;
 	DFS_CACHE_TGT_LIST(tl);
 	int num_targets = 0;
 	int rc = 0;
@@ -505,10 +505,8 @@ static int reconnect_dfs_server(struct TCP_Server_Info *server)
 	 * through /proc/fs/cifs/dfscache or the target list is empty due to server settings after
 	 * refreshing the referral, so, in this case, default it to 1.
 	 */
-	mutex_lock(&server->refpath_lock);
-	if (!dfs_cache_noreq_find(server->leaf_fullpath + 1, NULL, &tl))
+	if (!dfs_cache_noreq_find(ref_path, NULL, &tl))
 		num_targets = dfs_cache_get_nr_tgts(&tl);
-	mutex_unlock(&server->refpath_lock);
 	if (!num_targets)
 		num_targets = 1;
 
@@ -552,9 +550,7 @@ static int reconnect_dfs_server(struct TCP_Server_Info *server)
 		mod_delayed_work(cifsiod_wq, &server->reconnect, 0);
 	} while (server->tcpStatus == CifsNeedReconnect);
 
-	mutex_lock(&server->refpath_lock);
-	dfs_cache_noreq_update_tgthint(server->leaf_fullpath + 1, target_hint);
-	mutex_unlock(&server->refpath_lock);
+	dfs_cache_noreq_update_tgthint(ref_path, target_hint);
 	dfs_cache_free_tgts(&tl);
 
 	/* Need to set up echo worker again once connection has been established */
@@ -569,13 +565,8 @@ static int reconnect_dfs_server(struct TCP_Server_Info *server)
 
 int cifs_reconnect(struct TCP_Server_Info *server, bool mark_smb_session)
 {
-	mutex_lock(&server->refpath_lock);
-	if (!server->leaf_fullpath) {
-		mutex_unlock(&server->refpath_lock);
+	if (!server->leaf_fullpath)
 		return __cifs_reconnect(server, mark_smb_session);
-	}
-	mutex_unlock(&server->refpath_lock);
-
 	return reconnect_dfs_server(server);
 }
 #else
@@ -1754,9 +1745,6 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx,
 	INIT_DELAYED_WORK(&tcp_ses->echo, cifs_echo_request);
 	INIT_DELAYED_WORK(&tcp_ses->reconnect, smb2_reconnect_server);
 	mutex_init(&tcp_ses->reconnect_mutex);
-#ifdef CONFIG_CIFS_DFS_UPCALL
-	mutex_init(&tcp_ses->refpath_lock);
-#endif
 	memcpy(&tcp_ses->srcaddr, &ctx->srcaddr,
 	       sizeof(tcp_ses->srcaddr));
 	memcpy(&tcp_ses->dstaddr, &ctx->dstaddr,

fs/smb/client/dfs_cache.c

@@ -1141,13 +1141,11 @@ static char *get_ses_refpath(struct cifs_ses *ses)
 	struct TCP_Server_Info *server = ses->server;
 	char *path = ERR_PTR(-ENOENT);
 
-	mutex_lock(&server->refpath_lock);
 	if (server->leaf_fullpath) {
-		path = kstrdup(server->leaf_fullpath + 1, GFP_ATOMIC);
+		path = kstrdup(server->leaf_fullpath + 1, GFP_KERNEL);
 		if (!path)
 			path = ERR_PTR(-ENOMEM);
 	}
-	mutex_unlock(&server->refpath_lock);
 	return path;
 }