cifs: handle prefix paths in reconnect

For the case where we have a DFS path like below and we're currently
connected to targetA:

    //dfsroot/link -> //targetA/share/foo, //targetB/share/bar

after failover, we should make sure to update cifs_sb->prepath so the
next operations will use the new prefix path "/bar".

Besides, in order to simplify the use of different prefix paths,
enforce CIFS_MOUNT_USE_PREFIX_PATH for DFS mounts so we don't have to
revalidate the root dentry every time we set a new prefix path.

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

1 files changed, 15 insertions, 4 deletions

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 6f6fb3606a5d..6e95ee69dd18 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -162,9 +162,18 @@ static int __cifs_reconnect_tcon(const struct nls_table *nlsc,
 
 	for (it = dfs_cache_get_tgt_iterator(&tl); it;
 	     it = dfs_cache_get_next_tgt(&tl, it)) {
-		const char *tgt = dfs_cache_get_tgt_name(it);
+		const char *share, *prefix;
+		size_t share_len, prefix_len;
 
-		extract_unc_hostname(tgt, &dfs_host, &dfs_host_len);
+		rc = dfs_cache_get_tgt_share(it, &share, &share_len, &prefix,
+					     &prefix_len);
+		if (rc) {
+			cifs_dbg(VFS, "%s: failed to parse target share %d\n",
+				 __func__, rc);
+			continue;
+		}
+
+		extract_unc_hostname(share, &dfs_host, &dfs_host_len);
 
 		if (dfs_host_len != tcp_host_len
 		    || strncasecmp(dfs_host, tcp_host, dfs_host_len) != 0) {
@@ -175,11 +184,13 @@ static int __cifs_reconnect_tcon(const struct nls_table *nlsc,
 			continue;
 		}
 
-		scnprintf(tree, MAX_TREE_SIZE, "\\%s", tgt);
+		scnprintf(tree, MAX_TREE_SIZE, "\\%.*s", (int)share_len, share);
 
 		rc = CIFSTCon(0, tcon->ses, tree, tcon, nlsc);
-		if (!rc)
+		if (!rc) {
+			rc = update_super_prepath(tcon, prefix, prefix_len);
 			break;
+		}
 		if (rc == -EREMOTE)
 			break;
 	}