linux-kernel - Re: [PATCH v12 13/13] dm: add power-of-2 target for zoned devices with non power-of-2 zone sizes

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Message-ID: <ea7e7c1c-b47a-6c3a-edce-502b58cc440e@samsung.com>
Date:   Tue, 30 Aug 2022 12:03:54 +0200
From:   Pankaj Raghav <p.raghav@...sung.com>
To:     Shinichiro Kawasaki <shinichiro.kawasaki@....com>
CC:     "agk@...hat.com" <agk@...hat.com>,
        "snitzer@...nel.org" <snitzer@...nel.org>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        "damien.lemoal@...nsource.wdc.com" <damien.lemoal@...nsource.wdc.com>,
        "hch@....de" <hch@....de>,
        "pankydev8@...il.com" <pankydev8@...il.com>,
        Johannes Thumshirn <Johannes.Thumshirn@....com>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "dm-devel@...hat.com" <dm-devel@...hat.com>,
        "hare@...e.de" <hare@...e.de>,
        "jaegeuk@...nel.org" <jaegeuk@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Matias Bjørling <Matias.Bjorling@....com>,
        "gost.dev@...sung.com" <gost.dev@...sung.com>,
        "bvanassche@....org" <bvanassche@....org>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
        Damien Le Moal <Damien.LeMoal@....com>
Subject: Re: [PATCH v12 13/13] dm: add power-of-2 target for zoned devices
 with non power-of-2 zone sizes

On 2022-08-30 04:52, Shinichiro Kawasaki wrote:
> On Aug 23, 2022 / 14:18, Pankaj Raghav wrote:
>> Only zoned devices with power-of-2(po2) number of sectors per zone(zone
>> size) were supported in linux but now non power-of-2(npo2) zone sizes
>> support has been added to the block layer.
>>
>> Filesystems such as F2FS and btrfs have support for zoned devices with
>> po2 zone size assumption. Before adding native support for npo2 zone
>> sizes, it was suggested to create a dm target for npo2 zone size device to
>> appear as a po2 zone size target so that file systems can initially
>> work without any explicit changes by using this target.
> 
> FYI, with this patch series, I created the new dm target and ran blktests zbd
> group for it. And I observed zbd/007 test case failure (other test cases
> passed). The test checks sector mapping of zoned dm-linear, dm-flakey and dm-
> crypt. Some changes in the test case look required to handle the new target.
> 
Thanks for testing it. I am aware of this test case, and I skipped it while
I was testing my target.

The test needs to be adapted as the container's start, and the logical
device's start will be different for this target.

I initially thought this test case might not apply to the dm-po2zone
target, but at a closer look, it is helpful once the zone offset is adapted
while doing a reset and writing data as the test only verifies the relative
WP position.

I also noticed that this test relies on getting the underlying device id
using `dmsetup table` command. The target currently lacks the `.status`
callback which appends the device id details. I will add them as a part of
the next revision for this target. Thanks.