Re: [PATCH v2 0/3] btrfs-progs: check: add detection for missing root orphan items

[Boris Burkov <boris@bur.io>]

On Sun, Jul 27, 2025 at 08:02:59AM +0930, Qu Wenruo wrote:
> [CHANGELOG]
> v2:
> - Enhance the original mode to detect any refs mismatch
>   Thus even if the root item has 0 refs but we find some unexpected
>   backref, then it will also report it as an error.
> 
>   Thanks Boris for point this out.
> 
> There is an internal bug report that some half-dropped subvolume makes
> balance to fail.
> 
> It turns out that, the involved subvolume doesn't have an orphan item,
> this means the half-dropped subvolume is never going to be cleaned up.
> 
> Then at balance time, a reloc tree is created for that half-dropped
> subvolume, and since balance doesn't expect to get a half-dropped
> subvolume, it doesn't check the drop_process_key and increased ref on
> already dropped nodes.
> 
> The problem for progs is that, neither original mode nor lowmem detects
> this kind of problem.
> 
> Original mode has a bad logic which prevents us from calling the proper
> orphan item check.
> Lowmem mode doesn't even take orphan item into consideration.
> 
> This series will add the detection part for btrfs-check, for both
> original and lowmem mode, with a hand crafted image for test.

Reviewed-by: Boris Burkov <boris@bur.io>

> 
> 
> Qu Wenruo (3):
>   btrfs-progs: check/original: detect missing orphan items correctly
>   btrfs-progs: check/lowmem: detect missing orphan items correctly
>   btrfs-progs: fsck-tests: a new test case for missing root orphan item
> 
>  check/main.c                                  |  39 +++++++++++-------
>  check/mode-lowmem.c                           |  11 +++++
>  check/mode-original.h                         |   3 ++
>  .../default.img.xz                            | Bin 0 -> 13468 bytes
>  .../066-missing-root-orphan-item/test.sh      |  14 +++++++
>  5 files changed, 51 insertions(+), 16 deletions(-)
>  create mode 100644 tests/fsck-tests/066-missing-root-orphan-item/default.img.xz
>  create mode 100755 tests/fsck-tests/066-missing-root-orphan-item/test.sh
> 
> --
> 2.50.1
>