From 0571c857fe326141e35162f5a05e6b89789840bf Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <djwong@kernel.org>
Date: Thu, 28 Apr 2022 15:39:02 -0400
Subject: [PATCH] xfs: fix maxlevels comparisons in the btree staging code

Source kernel commit: 78e8ec83a404d63dcc86b251f42e4ee8aff27465

The btree geometry computation function has an off-by-one error in that
it does not allow maximally tall btrees (nlevels == XFS_BTREE_MAXLEVELS).
This can result in repairs failing unnecessarily on very fragmented
filesystems.  Subsequent patches to remove MAXLEVELS usage in favor of
the per-btree type computations will make this a much more likely
occurrence.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
---
 libxfs/xfs_btree_staging.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libxfs/xfs_btree_staging.c b/libxfs/xfs_btree_staging.c
index 146d247..daf9979 100644
--- a/libxfs/xfs_btree_staging.c
+++ b/libxfs/xfs_btree_staging.c
@@ -662,7 +662,7 @@ xfs_btree_bload_compute_geometry(
 	xfs_btree_bload_ensure_slack(cur, &bbl->node_slack, 1);
 
 	bbl->nr_records = nr_this_level = nr_records;
-	for (cur->bc_nlevels = 1; cur->bc_nlevels < XFS_BTREE_MAXLEVELS;) {
+	for (cur->bc_nlevels = 1; cur->bc_nlevels <= XFS_BTREE_MAXLEVELS;) {
 		uint64_t	level_blocks;
 		uint64_t	dontcare64;
 		unsigned int	level = cur->bc_nlevels - 1;
@@ -724,7 +724,7 @@ xfs_btree_bload_compute_geometry(
 		nr_this_level = level_blocks;
 	}
 
-	if (cur->bc_nlevels == XFS_BTREE_MAXLEVELS)
+	if (cur->bc_nlevels > XFS_BTREE_MAXLEVELS)
 		return -EOVERFLOW;
 
 	bbl->btree_height = cur->bc_nlevels;
-- 
1.8.3.1

