xfs: don't track firstrec/firstkey separately in xchk_btree

The btree scrubbing code checks that the records (or keys) that it finds
in a btree block are all in order by calling the btree cursor's
->recs_inorder function.  This of course makes no sense for the first
item in the block, so we switch that off with a separate variable in
struct xchk_btree.

Christoph helped me figure out that the variable is unnecessary, since
we just accessed bc_ptrs[level] and can compare that against zero.  Use
that, and save ourselves some memory space.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/scrub/btree.c

@@ -141,9 +141,9 @@ xchk_btree_rec(
 	trace_xchk_btree_rec(bs->sc, cur, 0);
 
 	/* If this isn't the first record, are they in order? */
-	if (!bs->firstrec && !cur->bc_ops->recs_inorder(cur, &bs->lastrec, rec))
+	if (cur->bc_ptrs[0] > 1 &&
+	    !cur->bc_ops->recs_inorder(cur, &bs->lastrec, rec))
 		xchk_btree_set_corrupt(bs->sc, cur, 0);
-	bs->firstrec = false;
 	memcpy(&bs->lastrec, rec, cur->bc_ops->rec_len);
 
 	if (cur->bc_nlevels == 1)
@@ -188,10 +188,9 @@ xchk_btree_key(
 	trace_xchk_btree_key(bs->sc, cur, level);
 
 	/* If this isn't the first key, are they in order? */
-	if (!bs->firstkey[level] &&
+	if (cur->bc_ptrs[level] > 1 &&
 	    !cur->bc_ops->keys_inorder(cur, &bs->lastkey[level], key))
 		xchk_btree_set_corrupt(bs->sc, cur, level);
-	bs->firstkey[level] = false;
 	memcpy(&bs->lastkey[level], key, cur->bc_ops->key_len);
 
 	if (level + 1 >= cur->bc_nlevels)
@@ -636,7 +635,6 @@ xchk_btree(
 	struct xfs_buf			*bp;
 	struct check_owner		*co;
 	struct check_owner		*n;
-	int				i;
 	int				error = 0;
 
 	/*
@@ -649,13 +647,10 @@ xchk_btree(
 	bs->cur = cur;
 	bs->scrub_rec = scrub_fn;
 	bs->oinfo = oinfo;
-	bs->firstrec = true;
 	bs->private = private;
 	bs->sc = sc;
 
 	/* Initialize scrub state */
-	for (i = 0; i < XFS_BTREE_MAXLEVELS; i++)
-		bs->firstkey[i] = true;
 	INIT_LIST_HEAD(&bs->to_check);
 
 	/* Don't try to check a tree with a height we can't handle. */

fs/xfs/scrub/btree.h

@@ -39,9 +39,7 @@ struct xchk_btree {
 
 	/* internal scrub state */
 	union xfs_btree_rec		lastrec;
-	bool				firstrec;
 	union xfs_btree_key		lastkey[XFS_BTREE_MAXLEVELS];
-	bool				firstkey[XFS_BTREE_MAXLEVELS];
 	struct list_head		to_check;
 };
 int xchk_btree(struct xfs_scrub *sc, struct xfs_btree_cur *cur,