XFS: corruption fix

Fix nused counter.  It's currently getting set to -1 rather than getting
decremented by 1.  Since nused never reaches 0, the "if (!free->hdr.nused)"
check in xfs_dir2_leafn_remove() fails every time and xfs_dir2_shrink_inode()
doesn't get called when it should.  This causes extra blocks to be left on
an empty directory and the directory in unable to be converted back to
inline extent mode.
Signed-off-by: Mandy Kirkconnell <alkirkco@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

fs/xfs/xfs_dir2_node.c

@@ -970,7 +970,7 @@ xfs_dir2_leafn_remove(
 			/*
 			 * One less used entry in the free table.
 			 */
-			free->hdr.nused = cpu_to_be32(-1);
+			be32_add(&free->hdr.nused, -1);
 			xfs_dir2_free_log_header(tp, fbp);
 			/*
 			 * If this was the last entry in the table, we can