[PATCH] cifs_get_root shouldn't use path with tree name

[Sachin Prabhu <sprabhu-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

When a server returns the optional flag SMB_SHARE_IS_IN_DFS in response
to a tree connect, cifs_build_path_to_root() will return a pathname
which includes the tree name. This causes problems with cifs_get_root()
which separates each component and does a lookup for each component of
the path.

We encountered a problem with dfs shares hosted by a Netapp. when
connecting to nodes pointed to by the DFS share. The tree connect for
these nodes return SMB_SHARE_IS_IN_DFS even after the DFS node is
resolved and the node returned doesn't contain a DFS share. Other
servers(tested with MS Win2012 R2) do not and hence do not face this
problem. A workaround for Netapp servers is to mount with the
nodfs flag.
The return flag results in cifs_build_path_to_root() using the tree name
in building the path which is then split into its components and
individual lookup done for each component in cifs_get_root(). The first
component of the path in this case is the hostname which results in
object not found errors.

We have tested this patch both on our internal test servers as well as
the user's own servers and can confirm that it fixes the problem.

Signed-off-by: Sachin Prabhu <sprabhu-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Reported-by: Pierguido Lambri <plambri-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 fs/cifs/cifsfs.c    | 2 +-
 fs/cifs/cifsproto.h | 3 ++-
 fs/cifs/connect.c   | 3 ++-
 fs/cifs/dir.c       | 4 ++--
 4 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 6bbec5e..b6f57dd 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -610,7 +610,7 @@ cifs_get_root(struct smb_vol *vol, struct super_block *sb)
 	char sep;
 
 	full_path = cifs_build_path_to_root(vol, cifs_sb,
-					    cifs_sb_master_tcon(cifs_sb));
+				cifs_sb_master_tcon(cifs_sb), 0);
 	if (full_path == NULL)
 		return ERR_PTR(-ENOMEM);
 
diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 1243bd3..52c307b 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -63,7 +63,8 @@ extern void exit_cifs_spnego(void);
 extern char *build_path_from_dentry(struct dentry *);
 extern char *cifs_build_path_to_root(struct smb_vol *vol,
 				     struct cifs_sb_info *cifs_sb,
-				     struct cifs_tcon *tcon);
+				     struct cifs_tcon *tcon,
+				     int add_treename);
 extern char *build_wildcard_path_from_dentry(struct dentry *direntry);
 extern char *cifs_compose_mount_options(const char *sb_mountdata,
 		const char *fullpath, const struct dfs_info3_param *ref,
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 9878943..afca9ee 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -3649,7 +3649,8 @@ remote_path_check:
 		/*
 		 * cifs_build_path_to_root works only when we have a valid tcon
 		 */
-		full_path = cifs_build_path_to_root(volume_info, cifs_sb, tcon);
+		full_path = cifs_build_path_to_root(volume_info, cifs_sb, tcon,
+					tcon->Flags & SMB_SHARE_IS_IN_DFS);
 		if (full_path == NULL) {
 			rc = -ENOMEM;
 			goto mount_fail_check;
diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index 4716c54..4c0c62c 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -47,7 +47,7 @@ renew_parental_timestamps(struct dentry *direntry)
 
 char *
 cifs_build_path_to_root(struct smb_vol *vol, struct cifs_sb_info *cifs_sb,
-			struct cifs_tcon *tcon)
+			struct cifs_tcon *tcon, int add_treename)
 {
 	int pplen = vol->prepath ? strlen(vol->prepath) + 1 : 0;
 	int dfsplen;
@@ -59,7 +59,7 @@ cifs_build_path_to_root(struct smb_vol *vol, struct cifs_sb_info *cifs_sb,
 		return full_path;
 	}
 
-	if (tcon->Flags & SMB_SHARE_IS_IN_DFS)
+	if (add_treename)
 		dfsplen = strnlen(tcon->treeName, MAX_TREE_SIZE + 1);
 	else
 		dfsplen = 0;
-- 
2.5.5