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Subject: Re: [PATCH v3] null_blk: add support for max open/active zone limit
 for zoned devices
To:     Johannes Thumshirn <Johannes.Thumshirn@wdc.com>,
        Niklas Cassel <nks@flawful.org>, Jens Axboe <axboe@kernel.dk>
Cc:     Damien Le Moal <Damien.LeMoal@wdc.com>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Niklas Cassel <Niklas.Cassel@wdc.com>
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 <20200917075647.GA20845@flawful.org>
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From:   =?UTF-8?Q?Matias_Bj=c3=b8rling?= <mb@lightnvm.io>
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Date:   Tue, 29 Sep 2020 11:25:10 +0200
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On 23/09/2020 09.46, Johannes Thumshirn wrote:
> On 17/09/2020 09:57, Niklas Cassel wrote:
>> On Mon, Sep 07, 2020 at 08:18:26AM +0000, Niklas Cassel wrote:
>>> On Fri, Aug 28, 2020 at 12:54:00PM +0200, Niklas Cassel wrote:
>>>> Add support for user space to set a max open zone and a max active zone
>>>> limit via configfs. By default, the default values are 0 == no limit.
>>>>
>>>> Call the block layer API functions used for exposing the configured
>>>> limits to sysfs.
>>>>
>>>> Add accounting in null_blk_zoned so that these new limits are respected.
>>>> Performing an operation that would exceed these limits results in a
>>>> standard I/O error.
>>>>
>>>> A max open zone limit exists in the ZBC standard.
>>>> While null_blk_zoned is used to test the Zoned Block Device model in
>>>> Linux, when it comes to differences between ZBC and ZNS, null_blk_zoned
>>>> mostly follows ZBC.
>>>>
>>>> Therefore, implement the manage open zone resources function from ZBC,
>>>> but additionally add support for max active zones.
>>>> This enables user space not only to test against a device with an open
>>>> zone limit, but also to test against a device with an active zone limit.
>>>>
>>>> Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
>>>> Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
>>>> ---
>>>> Changes since v2:
>>>> -Picked up Damien's Reviewed-by tag.
>>>> -Fixed a typo in the commit message.
>>>> -Renamed null_manage_zone_resources() to null_has_zone_resources().
>>>>
>>>>   drivers/block/null_blk.h       |   5 +
>>>>   drivers/block/null_blk_main.c  |  16 +-
>>>>   drivers/block/null_blk_zoned.c | 319 +++++++++++++++++++++++++++------
>>>>   3 files changed, 282 insertions(+), 58 deletions(-)
>>> Hello Jens,
>>>
>>> A gentle ping on this.
>>>
>>> As far as I can tell, there are no outstanding review comments.
>>
>> Hello Jens,
>>
>> Pinging you from another address, in case my corporate email is getting
>> stuck in your spam filter.
>>
>> Kind regards,
>> Niklas
>>
>
> Jens,
>
> Any chance we can get this queued up for 5.10? This is really helpful for e.g.
> the zonefs test suite or xfstests when btrfs HMZONED support lands.
>
> Thanks,
> 	Johannes

Thanks, Niklas.

Reviewed-by: Matias Bjørling <matias.bjorling@wdc.com>