[PATCH 4/5] 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]
Also treat an extent item with the TREE_BLOCK flag as a tree block, and
take its owner from the tree block header.

Fixes: 5bd97022f384 ("btrfs-progs: check: add support for squota")
Signed-off-by: Siddharth Mishra <smish149@asu.edu>
---
 check/qgroup-verify.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/check/qgroup-verify.c b/check/qgroup-verify.c
index b58ef366..d6681653 100644
--- a/check/qgroup-verify.c
+++ b/check/qgroup-verify.c
@@ -1046,8 +1046,9 @@ 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 (!meta_item &&
+	    !(btrfs_extent_flags(leaf, ei) & BTRFS_EXTENT_FLAG_TREE_BLOCK)) {
+		type = btrfs_extent_inline_ref_type(leaf, iref);
 		if (type == BTRFS_EXTENT_OWNER_REF_KEY) {
 			struct btrfs_extent_owner_ref *oref;
 
-- 
2.54.0