namei.c : update mnt when it needed

update the mnt of the path when it is not equal to the new one.
Signed-off-by: Huang Shijie <shijie8@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namei.c

@@ -523,9 +523,10 @@ static void path_put_conditional(struct path *path, struct nameidata *nd)
 static inline void path_to_nameidata(struct path *path, struct nameidata *nd)
 {
 	dput(nd->path.dentry);
-	if (nd->path.mnt != path->mnt)
+	if (nd->path.mnt != path->mnt) {
 		mntput(nd->path.mnt);
-	nd->path.mnt = path->mnt;
+		nd->path.mnt = path->mnt;
+	}
 	nd->path.dentry = path->dentry;
 }