Re: [PATCH] dm thin metadata: fix superblock refcount leak on snapshot shadow failure

[Ming Hung Tsai]

On Sat, Jul 11, 2026 at 6:16 PM Genjian <zhanggenjian@xxxxxxx> wrote:
>
> From: Genjian Zhang <zhanggenjian@xxxxxxxxxx>
>
> __reserve_metadata_snap() increments THIN_SUPERBLOCK_LOCATION in the
> metadata space map before shadowing it. When dm_tm_shadow_block()
> fails, a reference is leaked in the metadata space map.
>
> Fix by adding the missing dm_sm_dec_block().
>
> Fixes: cc8394d86f04 ("dm thin: provide userspace access to pool metadata")
> Signed-off-by: Genjian Zhang <zhanggenjian@xxxxxxxxxx>
> ---

The fix looks reasonable as a best-effort cleanup for the immediate
refcount leak.