cifs: allow calling cifs_build_path_to_root on incomplete cifs_sb

It's possible that cifs_mount will call cifs_build_path_to_root on a
newly instantiated cifs_sb. In that case, it's likely that the
master_tlink pointer has not yet been instantiated.

Fix this by having cifs_build_path_to_root take a cifsTconInfo pointer
as well, and have the caller pass that in.

Reported-and-Tested-by: Robbert Kouprie <robbert@exx.nl>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

3 files changed, 6 insertions, 5 deletions

diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 5523047b1ebd..e6d1481b16c1 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -54,7 +54,8 @@ do {								\
              __func__, curr_xid, (int)rc);                      \
 } while (0)
 extern char *build_path_from_dentry(struct dentry *);
-extern char *cifs_build_path_to_root(struct cifs_sb_info *cifs_sb);
+extern char *cifs_build_path_to_root(struct cifs_sb_info *cifs_sb,
+                                        struct cifsTconInfo *tcon);
 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 387b91ae7400..cc1a8604a790 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -2833,7 +2833,7 @@ remote_path_check:
         /* check if a whole path (including prepath) is not remote */
         if (!rc && cifs_sb->prepathlen && tcon) {
                 /* build_path_to_root works only when we have a valid tcon */
-                full_path = cifs_build_path_to_root(cifs_sb);
+                full_path = cifs_build_path_to_root(cifs_sb, tcon);
                 if (full_path == NULL) {
                         rc = -ENOMEM;
                         goto mount_fail_check;
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index aa48521a78c1..589f3e3f6e00 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -728,12 +728,12 @@ static const struct inode_operations cifs_ipc_inode_ops = {
         .lookup = cifs_lookup,
 };
 
-char *cifs_build_path_to_root(struct cifs_sb_info *cifs_sb)
+char *cifs_build_path_to_root(struct cifs_sb_info *cifs_sb,
+                                struct cifsTconInfo *tcon)
 {
         int pplen = cifs_sb->prepathlen;
         int dfsplen;
         char *full_path = NULL;
-        struct cifsTconInfo *tcon = cifs_sb_master_tcon(cifs_sb);
 
         /* if no prefix path, simply set path to the root of share to "" */
         if (pplen == 0) {
@@ -875,7 +875,7 @@ struct inode *cifs_root_iget(struct super_block *sb, unsigned long ino)
         char *full_path;
         struct cifsTconInfo *tcon = cifs_sb_master_tcon(cifs_sb);
 
-        full_path = cifs_build_path_to_root(cifs_sb);
+        full_path = cifs_build_path_to_root(cifs_sb, tcon);
         if (full_path == NULL)
                 return ERR_PTR(-ENOMEM);