Re: [PATCH] md: ensure child flush IO does not affect origin bio->bi_status

[Song Liu]

On Wed, Sep 18, 2024 at 11:33 PM <linan666@xxxxxxxxxxxxxxx> wrote:
>
> From: Li Nan <linan122@xxxxxxxxxx>
>
> When a flush is issued to an RAID array, a child flush IO is created and
> issued for each member disk in the RAID array. Since commit b75197e86e6d
> ("md: Remove flush handling"), each child flush IO has been chained with
> the original bio. As a result, the failure of any child IO could modify
> the bi_status of the original bio, potentially impacting the upper-layer
> filesystem.
>
> Fix the issue by preventing child flush IO from altering the original
> bio->bi_status as before. However, this design introduces a known
> issue: in the event of a power failure, if a flush IO on a member
> disk fails, the upper layers may not be informed. This issue is not easy
> to fix and will not be addressed for the time being in this issue.
>
> Fixes: b75197e86e6d ("md: Remove flush handling")
> Signed-off-by: Li Nan <linan122@xxxxxxxxxx>

Applied to md-6.12.

Thanks for the fix!
Song