[PATCH] __d_path needs vfsmount_lock

From: Mike Waychison <Michael.Waychison@Sun.COM>

- protect vfsmount->mnt_parent by taking vfsmount_lock in __d_path

fs/dcache.c

@@ -1296,10 +1296,14 @@ static char * __d_path( struct dentry *dentry, struct vfsmount *vfsmnt,
 			break;
 		if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
 			/* Global root? */
-			if (vfsmnt->mnt_parent == vfsmnt)
+			spin_lock(&vfsmount_lock);
+			if (vfsmnt->mnt_parent == vfsmnt) {
+				spin_unlock(&vfsmount_lock);
 				goto global_root;
+			}
 			dentry = vfsmnt->mnt_mountpoint;
 			vfsmnt = vfsmnt->mnt_parent;
+			spin_unlock(&vfsmount_lock);
 			continue;
 		}
 		parent = dentry->d_parent;