linux-kernel - Re: [dm-devel] [PATCH v7 12/13] dm: call dm_zone_endio after the target endio callback for zoned devices

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Date:   Wed, 15 Jun 2022 20:01:36 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Pankaj Raghav <p.raghav@...sung.com>, hch@....de,
        snitzer@...hat.com, axboe@...nel.dk
Cc:     bvanassche@....org, pankydev8@...il.com, gost.dev@...sung.com,
        jiangbo.365@...edance.com, linux-nvme@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        dm-devel@...hat.com, jonathan.derrick@...ux.dev,
        Johannes.Thumshirn@....com, dsterba@...e.com, jaegeuk@...nel.org
Subject: Re: [dm-devel] [PATCH v7 12/13] dm: call dm_zone_endio after the
 target endio callback for zoned devices

On 6/15/22 19:19, Pankaj Raghav wrote:
> dm_zone_endio() updates the bi_sector of orig bio for zoned devices that
> uses either native append or append emulation and it is called before the
> endio of the target. But target endio can still update the clone bio
> after dm_zone_endio is called, thereby, the orig bio does not contain
> the updated information anymore. Call dm_zone_endio for zoned devices
> after calling the target's endio function
> 
> Signed-off-by: Pankaj Raghav <p.raghav@...sung.com>
> ---
> @Damien and @Hannes: I couldn't come up with a testcase that uses endio callback and
> zone append or append emulation for zoned devices to test for
> regression in this change. It would be great if you can suggest
> something. This change is required for the npo2 target as we update the
> clone bio sector in the endio callback function and the orig bio should
> be updated only after the endio callback for zone appends.

Running zonefs tests on top of dm-crypt will exercise DM zone append
emulation.

> 
>  drivers/md/dm.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 3f17fe1de..3a74e1038 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -1025,10 +1025,6 @@ static void clone_endio(struct bio *bio)
>  			disable_write_zeroes(md);
>  	}
>  
> -	if (static_branch_unlikely(&zoned_enabled) &&
> -	    unlikely(blk_queue_is_zoned(bdev_get_queue(bio->bi_bdev))))
> -		dm_zone_endio(io, bio);
> -
>  	if (endio) {
>  		int r = endio(ti, bio, &error);
>  		switch (r) {
> @@ -1057,6 +1053,10 @@ static void clone_endio(struct bio *bio)
>  		}
>  	}
>  
> +	if (static_branch_unlikely(&zoned_enabled) &&
> +	    unlikely(blk_queue_is_zoned(bdev_get_queue(bio->bi_bdev))))

blk_queue_is_zoned(bdev_get_queue(bio->bi_bdev))) ->
bdev_is_zoned(bio->bi_bdev)

> +		dm_zone_endio(io, bio);
> +
>  	if (static_branch_unlikely(&swap_bios_enabled) &&
>  	    unlikely(swap_bios_limit(ti, bio)))
>  		up(&md->swap_bios_semaphore);


-- 
Damien Le Moal
Western Digital Research