xfs: don't load local xattr values during scrub

Local extended attributes store their values within the same leaf block.
There's no header for the values themselves, nor are they separately
checksummed.  Hence we can save a bit of time in the attr scrubber by
not wasting time retrieving the values.

Regrettably, shortform attributes do not set XFS_ATTR_LOCAL so this
offers us no advantage there, but at least there are very few attrs in
that case.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/scrub/attr.c

@@ -200,6 +200,14 @@ xchk_xattr_listent(
 		goto fail_xref;
 	}
 
+	/*
+	 * Local xattr values are stored in the attr leaf block, so we don't
+	 * need to retrieve the value from a remote block to detect corruption
+	 * problems.
+	 */
+	if (flags & XFS_ATTR_LOCAL)
+		goto fail_xref;
+
 	/*
 	 * Try to allocate enough memory to extrat the attr value.  If that
 	 * doesn't work, we overload the seen_enough variable to convey