xfs: fix maxlevels comparisons in the btree staging code

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>

diff --git a/fs/xfs/libxfs/xfs_btree_staging.c b/fs/xfs/libxfs/xfs_btree_staging.c
index ac9e801..89c8a14 100644 (file)
--- a/fs/xfs/libxfs/xfs_btree_staging.c
+++ b/fs/xfs/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;