Re: [PATCH] block: clear zone write plugging flag before failing rejected BIOs

[Damien Le Moal <dlemoal@kernel.org>]

On 2026/06/07 11:18, Jackie Liu wrote:
> From: Jackie Liu <liuyun01@kylinos.cn>
> 
> Commit fe0418eb9bd6 ("block: Prevent potential deadlocks in zone write plug
> error recovery") changed blk_zone_wplug_handle_write() to fail BIOs
> directly when blk_zone_wplug_prepare_bio() rejects them, for example
> because the write is not aligned to the cached write pointer or the plug
> needs a write pointer update. However, the BIO is already marked with
> BIO_ZONE_WRITE_PLUGGING at that point even though it is not issued.
> 
> Completing such a BIO with bio_io_error() makes bio_endio() call
> blk_zone_write_plug_bio_endio(), which treats the completion as a failed
> device write and may poison the cached zone write pointer state by setting
> BLK_ZONE_WPLUG_NEED_WP_UPDATE.

Yes, true. But you did not explain clearly why that is a problem. After all, if
we hit this case, the user issued an unaligned BIO, and so forcing it to do a
report zones to get everything in sync and the correct write pointer is not a
bad thing.

If fe0418eb9bd6 change is actually causing you problems, please describe that
problem clearly. But ideally, I do not want to special case some error
completions over others and prefer to have a single error path that result in
the same state for the zone write plugs, regardless of a write error root cause.

> 
> Clear BIO_ZONE_WRITE_PLUGGING and drop the zone write plug reference before
> failing the rejected BIO.
> 
> Fixes: fe0418eb9bd6 ("block: Prevent potential deadlocks in zone write plug error recovery")
> Cc: stable@vger.kernel.org # 6.13+
> Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
> ---
>  block/blk-zoned.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> index 6a221c180889..855767d8bfc1 100644
> --- a/block/blk-zoned.c
> +++ b/block/blk-zoned.c
> @@ -1502,7 +1502,9 @@ static bool blk_zone_wplug_handle_write(struct bio *bio, unsigned int nr_segs)
>  		goto queue_bio;
>  
>  	if (!blk_zone_wplug_prepare_bio(zwplug, bio)) {
> +		bio_clear_flag(bio, BIO_ZONE_WRITE_PLUGGING);
>  		spin_unlock_irqrestore(&zwplug->lock, flags);
> +		disk_put_zone_wplug(zwplug);
>  		bio_io_error(bio);
>  		return true;
>  	}


-- 
Damien Le Moal
Western Digital Research