vfs: prefer ->dentry->d_sb to ->mnt->mnt_sb

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 2a1a9e6..b739b21 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4781,7 +4781,7 @@
 		return -EINVAL;
 
 	/* Quotafile not on the same filesystem? */
-	if (path->mnt->mnt_sb != sb)
+	if (path->dentry->d_sb != sb)
 		return -EXDEV;
 	/* Journaling quota? */
 	if (EXT4_SB(sb)->s_qf_names[type]) {