cifs: only update prefix path of DFS links in cifs_tree_connect()

For DFS root mounts that contain a prefix path, do not change them
after failover.

E.g., if the user mounts

	//srvA/root/dir1

and then lost connection to srvA, it will reconnect to

	//srvB/root/dir1

In case of DFS links, which may resolve to different prefix paths
depending on their list of targets, the following must be supported:

	- mount //srvA/root/link/bar
	- connect to //srvA/share
	- set prefix path to "bar"
	- lost connection to srvA
	- reconnect to next target: //srvB/share/foo
	- set new prefix path to "foo/bar"

In cifs_tree_connect(), check the server_type field of the cached DFS
referral to determine whether or not prefix path should be updated.

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index aae9095..637ba00 100644 (file)
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -5548,6 +5548,8 @@ int cifs_tree_connect(const unsigned int xid, struct cifs_tcon *tcon, const stru
        const char *dfs_host;
        size_t dfs_host_len;
        char *share = NULL, *prefix = NULL;
+       struct dfs_info3_param ref = {0};
+       bool isroot;
 
        tree = kzalloc(MAX_TREE_SIZE, GFP_KERNEL);
        if (!tree)
@@ -5563,9 +5565,11 @@ int cifs_tree_connect(const unsigned int xid, struct cifs_tcon *tcon, const stru
                goto out;
        }
 
-       rc = dfs_cache_noreq_find(tcon->dfs_path + 1, NULL, &tl);
+       rc = dfs_cache_noreq_find(tcon->dfs_path + 1, &ref, &tl);
        if (rc)
                goto out;
+       isroot = ref.server_type == DFS_TYPE_ROOT;
+       free_dfs_info_param(&ref);
 
        extract_unc_hostname(server->hostname, &tcp_host, &tcp_host_len);
 
@@ -5609,7 +5613,8 @@ int cifs_tree_connect(const unsigned int xid, struct cifs_tcon *tcon, const stru
                } else {
                        scnprintf(tree, MAX_TREE_SIZE, "\\%s", share);
                        rc = ops->tree_connect(xid, tcon->ses, tree, tcon, nlsc);
-                       if (!rc) {
+                       /* Only handle prefix paths of DFS link targets */
+                       if (!rc && !isroot) {
                                rc = update_super_prepath(tcon, prefix);
                                break;
                        }