[PATCH v2 09/12] btrfs-progs: make check detect and fix problems with super_bytes_used

[Josef Bacik <josef@toxicpanda.com>]

We do not detect problems with our bytes_used counter in the super
block.  Thankfully the same method to fix block groups is used to re-set
the value in the super block, so simply add some extra code to validate
the bytes_used field and then piggy back on the repair code for block
groups.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 check/main.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/check/main.c b/check/main.c
index af9e0ff3..b1b1b866 100644
--- a/check/main.c
+++ b/check/main.c
@@ -8663,12 +8663,14 @@ static int check_block_groups(struct block_group_tree *bg_cache)
 	struct btrfs_trans_handle *trans;
 	struct cache_extent *item;
 	struct block_group_record *bg_rec;
+	u64 used = 0;
 	int ret = 0;
 
 	for (item = first_cache_extent(&bg_cache->tree); item;
 	     item = next_cache_extent(item)) {
 		bg_rec = container_of(item, struct block_group_record,
 				      cache);
+		used += bg_rec->actual_used;
 		if (bg_rec->disk_used == bg_rec->actual_used)
 			continue;
 		fprintf(stderr,
@@ -8678,6 +8680,19 @@ static int check_block_groups(struct block_group_tree *bg_cache)
 		ret = -1;
 	}
 
+	/*
+	 * We check the super bytes_used here because it's the sum of all block
+	 * groups used, and the repair actually happens in
+	 * btrfs_fix_block_accounting, so we can kill both birds with the same
+	 * stone here.
+	 */
+	if (used != btrfs_super_bytes_used(gfs_info->super_copy)) {
+		fprintf(stderr,
+			"super bytes used %llu mismatches actual used %llu\n",
+			btrfs_super_bytes_used(gfs_info->super_copy), used);
+		ret = -1;
+	}
+
 	if (!repair || !ret)
 		return ret;
 
-- 
2.26.3