linux-kernel - Re: [PATCH 7/7] dm: call dm_zone_endio after the target endio callback for zoned devices

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Message-ID: <20230110065822.GF10289@lst.de>
Date:   Tue, 10 Jan 2023 07:58:22 +0100
From:   Christoph Hellwig <hch@....de>
To:     Pankaj Raghav <p.raghav@...sung.com>
Cc:     axboe@...nel.dk, kernel@...kajraghav.com,
        linux-kernel@...r.kernel.org, hare@...e.de, bvanassche@....org,
        snitzer@...nel.org, dm-devel@...hat.com,
        damien.lemoal@...nsource.wdc.com, linux-nvme@...ts.infradead.org,
        hch@....de, linux-block@...r.kernel.org, gost.dev@...sung.com
Subject: Re: [PATCH 7/7] dm: call dm_zone_endio after the target endio
 callback for zoned devices

On Fri, Jan 06, 2023 at 09:33:17AM +0100, 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.
> 
> Currently, this is not a problem as the targets that support zoned devices
> such as dm-zoned, dm-linear, and dm-crypt do not have an endio function,
> and even if they do (such as dm-flakey), they don't modify the
> bio->bi_iter.bi_sector of the cloned bio that is used to update the
> orig_bio's bi_sector in dm_zone_endio function.
> 
> Call dm_zone_endio for zoned devices after calling the target's endio
> function.

This looks sensible, but I fail to see why we need this or how it fits
into the earlier block layer part of the series.