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Subject: Re: [PATCH v2] null_blk: add support for max open/active zone limit
 for zoned devices
To:     Niklas Cassel <niklas.cassel@wdc.com>, Jens Axboe <axboe@kernel.dk>
Cc:     damien.lemoal@wdc.com, johannes.thumshirn@wdc.com,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20200827135018.63644-1-niklas.cassel@wdc.com>
From:   Randy Dunlap <rdunlap@infradead.org>
Message-ID: <6d9fb163-f9d9-1f2d-d88c-db9d3a6185b4@infradead.org>
Date:   Thu, 27 Aug 2020 07:51:38 -0700
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On 8/27/20 6:50 AM, 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.

Hi,

How does a user find out about how to use/set these limits?


> 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 operating 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>
> ---
> Changes since v1:
> -Fixed review comments by Damien Le Moal.
> 
>  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(-)

thanks.
-- 
~Randy