[PATCH 6.1 090/280] btrfs: fix missing fields in superblock backup with BLOCK_GROUP_TREE

Greg Kroah-Hartman
2026-02-04T15:10:05Z

From: Mark Harmstone <mark@harmstone.com>

[ Upstream commit 1d8f69f453c2e8a2d99b158e58e02ed65031fa6d ]

When the BLOCK_GROUP_TREE compat_ro flag is set, the extent root and
csum root fields are getting missed.

This is because EXTENT_TREE_V2 treated these differently, and when
they were split off this special-casing was mistakenly assigned to
BGT rather than the rump EXTENT_TREE_V2. There's no reason why the
existence of the block group tree should mean that we don't record the
details of the last commit's extent root and csum root.

Fix the code in backup_super_roots() so that the correct check gets
made.

Fixes: 1c56ab991903 ("btrfs: separate BLOCK_GROUP_TREE compat RO flag from EXTENT_TREE_V2")
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Mark Harmstone <mark@harmstone.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/btrfs/disk-io.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 8576ba4aa0b7d..52e083b63070d 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1993,7 +1993,7 @@ static void backup_super_roots(struct btrfs_fs_info *info)
btrfs_set_backup_chunk_root_level(root_backup,
btrfs_header_level(info->chunk_root->node));

- if (!btrfs_fs_compat_ro(info, BLOCK_GROUP_TREE)) {
+ if (!btrfs_fs_incompat(info, EXTENT_TREE_V2)) {
struct btrfs_root *extent_root = btrfs_extent_root(info, 0);
struct btrfs_root *csum_root = btrfs_csum_root(info, 0);

--
2.51.0