linux-kernel - Re: [PATCH v6 2/4] Add support for SCT Write Same

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Date:   Mon, 22 Aug 2016 17:07:52 -0500
From:   Shaun Tancheff <shaun.tancheff@...gate.com>
To:     Tom Yan <tom.ty89@...il.com>
Cc:     Shaun Tancheff <shaun@...cheff.com>, linux-ide@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>, Tejun Heo <tj@...nel.org>,
        Christoph Hellwig <hch@....de>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Damien Le Moal <damien.lemoal@...t.com>,
        Hannes Reinecke <hare@...e.de>,
        Josh Bingaman <josh.bingaman@...gate.com>,
        Hannes Reinecke <hare@...e.com>
Subject: Re: [PATCH v6 2/4] Add support for SCT Write Same

On Mon, Aug 22, 2016 at 3:14 PM, Tom Yan <tom.ty89@...il.com> wrote:
> On 23 August 2016 at 03:43, Shaun Tancheff <shaun.tancheff@...gate.com> wrote:
>>
>> Why would we enforce upper level limits on something that doesn't
>> have any?
>
> If we advertise a limit in our SATL, it makes sense that we should
> make sure the behaviour is consistent when we issue a write same
> through the block layer / ioctl and when we issue a SCSI Write Same
> command directly (e.g. with sg_write_same). IMHO that's pretty much
> why SBC would mandate such behaviour as well.

Breaking would be advertising a limit that is too high and failing.
Advertising a lower limit and succeeding may not be ideal for all
possible use cases, but it's not breaking behaviour.

>>
>> If the upper level, or SG_IO, chooses to set a timeout of 10 hours and
>> wipe a whole disk it should be free to do so.
>>
>
> That's why I said, "if you are going to advertise an Maximum Write Same Length".

-- 
Shaun Tancheff