[PATCH 3/3] btrfs: Enhance the error outputting for write time tree checker

[Qu Wenruo]

Unlike read time tree checker error, write time error can't be inspected
by "btrfs ins dump-tree", so we need extra info to determine what's
going wrong.

The patch will add the following output for write time tree checker
error:
- The content of the offending tree block
  To help determining if it's a false alert.

- Kernel WARN_ON() for debug build
  This is helpful for us to detect unexpected write time tree checker
  error, especially fstests could catch the dmesg.
  Since the WARN_ON() is only triggered for write time tree checker,
  test cases utilizing dm-error won't trigger this WARN_ON(), thus no
  extra noise.

Signed-off-by: Qu Wenruo <w...@suse.com>
---
 fs/btrfs/disk-io.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 16dc60b4966d..a0925b4e00af 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -545,9 +545,11 @@ static int csum_dirty_buffer(struct btrfs_fs_info 
*fs_info, struct page *page)
                ret = btrfs_check_leaf_full(eb);
 
        if (ret < 0) {
+               btrfs_print_tree(eb, 0);
                btrfs_err(fs_info,
                "block=%llu write time tree block corruption detected",
                          eb->start);
+               WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG));
                return ret;
        }
        write_extent_buffer(eb, result, 0, csum_size);
-- 
2.23.0