vfs: new helper - vfs_ustat()

... and bury user_get_super()/statfs_by_dentry() - they are
purely internal now.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/parisc/hpux/sys_hpux.c b/arch/parisc/hpux/sys_hpux.c
index 6ab9580..d9dc6cd 100644
--- a/arch/parisc/hpux/sys_hpux.c
+++ b/arch/parisc/hpux/sys_hpux.c
@@ -136,16 +136,9 @@
  */
 static int hpux_ustat(dev_t dev, struct hpux_ustat __user *ubuf)
 {
-	struct super_block *s;
 	struct hpux_ustat tmp;  /* Changed to hpux_ustat */
 	struct kstatfs sbuf;
-	int err = -EINVAL;
-
-	s = user_get_super(dev);
-	if (s == NULL)
-		goto out;
-	err = statfs_by_dentry(s->s_root, &sbuf);
-	drop_super(s);
+	int err = vfs_ustat(dev, &sbuf);
 	if (err)
 		goto out;