[PATCH v2] btrfs-progs: check: count non-skinny tree blocks in simple quotas

[Siddharth Mishra <smish149@asu.edu>]

[BUG]
On a filesystem without skinny-metadata, mkfs with simple quotas writes
a qgroup that does not count the tree block of the fs tree:

  $ mkfs.btrfs -O squota,^skinny-metadata $dev
  $ btrfs inspect-internal dump-tree -t quota $dev
	item 1 key (0 QGROUP_INFO 0/5) itemoff 16203 itemsize 40
		generation 11
		referenced 0 referenced_compressed 0
		^^^^^^^^^^^^
		exclusive 0 exclusive_compressed 0

The kernel then warns about a squota underflow when the block is freed,
and "btrfs check" reports no error, because it uses the same code.

[CAUSE]
simple_quota_account_extent() treats an extent as a tree block only if
its key is METADATA_ITEM. Without skinny-metadata a tree block is an
EXTENT_ITEM with the TREE_BLOCK flag, so it is handled like data: its
first inline ref is a TREE_BLOCK_REF, not an owner ref, and the block is
not counted. mkfs fills the qgroups with the same code.

[FIX]
Pass whether the extent is a tree block, from its TREE_BLOCK flag,
instead of whether its key is METADATA_ITEM, so a tree block without
skinny-metadata also takes its owner from the tree block header.

Fixes: 5bd97022f384 ("btrfs-progs: check: add support for squota")
Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Siddharth Mishra <smish149@asu.edu>
---
v2:
- Pass the TREE_BLOCK flag from add_inline_refs() instead of checking it
  in simple_quota_account_extent() (Boris)

An AI tool helped with this version.
Tested as v1 (mkfs and check on skinny and non-skinny images, a
kernel-written filesystem, the btrfs-progs test suites), with no change
in results.

 check/qgroup-verify.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/check/qgroup-verify.c b/check/qgroup-verify.c
index b58ef366..30f258a2 100644
--- a/check/qgroup-verify.c
+++ b/check/qgroup-verify.c
@@ -1033,7 +1033,7 @@ static int simple_quota_account_extent(struct btrfs_fs_info *info,
 				       struct btrfs_key *key,
 				       struct btrfs_extent_item *ei,
 				       struct btrfs_extent_inline_ref *iref,
-				       u64 bytenr, u64 num_bytes, int meta_item)
+				       u64 bytenr, u64 num_bytes, bool is_metadata)
 {
 	u64 generation;
 	int type;
@@ -1046,8 +1046,8 @@ static int simple_quota_account_extent(struct btrfs_fs_info *info,
 	if (generation < counts.enable_gen)
 		return 0;
 
-	type = btrfs_extent_inline_ref_type(leaf, iref);
-	if (!meta_item) {
+	if (!is_metadata) {
+		type = btrfs_extent_inline_ref_type(leaf, iref);
 		if (type == BTRFS_EXTENT_OWNER_REF_KEY) {
 			struct btrfs_extent_owner_ref *oref;
 
@@ -1105,7 +1105,8 @@ static int add_inline_refs(struct btrfs_fs_info *info,
 
 	if (counts.simple) {
 		int ret = simple_quota_account_extent(info, ei_leaf, &key, ei, iref,
-						      bytenr, num_bytes, meta_item);
+				bytenr, num_bytes,
+				flags & BTRFS_EXTENT_FLAG_TREE_BLOCK);
 
 		if (ret)
 			error("squota account extent error: %d", ret);

base-commit: 3737c2603af86f742986c51cf0e5c4898a126d6f
-- 
2.54.0