[PATCH v3 7/9] btrfs-progs: check: detect issues with btrfs_super_used in lowmem check

[Josef Bacik <josef@toxicpanda.com>]

We can already fix this problem with the block accounting code, we just
need to keep track of how much we should have used on the file system,
and then check it against the bytes_super.  The repair just piggy backs
on the block group used repair.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 check/mode-lowmem.c | 13 ++++++++++++-
 check/mode-lowmem.h |  1 +
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/check/mode-lowmem.c b/check/mode-lowmem.c
index cb8e3ab8..a1ad9606 100644
--- a/check/mode-lowmem.c
+++ b/check/mode-lowmem.c
@@ -28,6 +28,7 @@
 #include "check/mode-lowmem.h"
 
 static u64 last_allocated_chunk;
+static u64 total_used = 0;
 
 static int calc_extent_flag(struct btrfs_root *root, struct extent_buffer *eb,
 			    u64 *flags_ret)
@@ -3645,6 +3646,8 @@ next:
 out:
 	btrfs_release_path(&path);
 
+	total_used += used;
+
 	if (total != used) {
 		error(
 		"block group[%llu %llu] used %llu but extent items used %llu",
@@ -5547,6 +5550,14 @@ next:
 	}
 out:
 
+	if (total_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),
+			total_used);
+		err |= SUPER_BYTES_USED_ERROR;
+	}
+
 	if (repair) {
 		ret = end_avoid_extents_overwrite();
 		if (ret < 0)
@@ -5559,7 +5570,7 @@ out:
 		if (ret)
 			err |= ret;
 		else
-			err &= ~BG_ACCOUNTING_ERROR;
+			err &= ~(BG_ACCOUNTING_ERROR|SUPER_BYTES_USED_ERROR);
 	}
 
 	btrfs_release_path(&path);
diff --git a/check/mode-lowmem.h b/check/mode-lowmem.h
index da9f8600..0bcc338b 100644
--- a/check/mode-lowmem.h
+++ b/check/mode-lowmem.h
@@ -48,6 +48,7 @@
 #define DIR_ITEM_HASH_MISMATCH	(1<<24) /* Dir item hash mismatch */
 #define INODE_MODE_ERROR	(1<<25) /* Bad inode mode */
 #define INVALID_GENERATION	(1<<26)	/* Generation is too new */
+#define SUPER_BYTES_USED_ERROR	(1<<27)	/* Super bytes_used is invalid */
 
 /*
  * Error bit for low memory mode check.
-- 
2.26.3