linux-kernel - Re: [PATCH v8 10/11] dm: call dm_zone_endio after the target endio callback for zoned devices

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Date:   Fri, 29 Jul 2022 10:48:06 +0200
From:   Pankaj Raghav <p.raghav@...sung.com>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>, <hch@....de>,
        <axboe@...nel.dk>, <snitzer@...nel.org>,
        <Johannes.Thumshirn@....com>
CC:     <matias.bjorling@....com>, <gost.dev@...sung.com>,
        <linux-kernel@...r.kernel.org>, <hare@...e.de>,
        <linux-block@...r.kernel.org>, <pankydev8@...il.com>,
        <bvanassche@....org>, <jaegeuk@...nel.org>, <dm-devel@...hat.com>,
        <linux-nvme@...ts.infradead.org>
Subject: Re: [PATCH v8 10/11] dm: call dm_zone_endio after the target endio
 callback for zoned devices

>>  	if (endio) {
>>  		int r = endio(ti, bio, &error);
>>  		switch (r) {
>> @@ -1155,6 +1151,10 @@ static void clone_endio(struct bio *bio)
>>  		}
>>  	}
>>  
>> +	if (static_branch_unlikely(&zoned_enabled) &&
>> +	    unlikely(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);
> 
> This patch seems completely unrelated to the series topic. Is that a bug
> fix ? How do you trigger it ? Our tests do not show any issues here...
> If this triggers only with non power of 2 zone size devices, then this
> should be squashed in patch 8. And patch 9 could also be squashed with
> patch 8 too.
> 
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.

This path is triggered only for the new target dm-po2zone and not for
npo2 zone size devices in general. I will mention this is a prep patch
for the new target because I wouldn't call it a bug per se.