From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jens Axboe <axboe@kernel.dk>
Subject: Re: [REGRESSION v4.10-rc1] blkdev_issue_zeroout() returns -EREMOTEIO
 on the first call for SCSI device that doesn't support WRITE SAME
Date: Fri, 3 Feb 2017 20:17:10 -0700
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To: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>, Junichi Nomura <j-nomura@ce.jp.nec.com>, "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>, linux-scsi <linux-scsi@vger.kernel.org>, Chaitanya Kulkarni <chaitanya.kulkarni@hgst.com>

On 02/03/2017 03:45 PM, Martin K. Petersen wrote:
>>>>>> "Jens" == Jens Axboe <axboe@kernel.dk> writes:
> 
>>> I think we should fix sd.c to only send WRITE SAME if either of the
>>> variants are explicitly listed as supported through REPORT SUPPORTED
>>> OPERATION CODES, or maybe through a whitelist if there are important
>>> enough devices.
> 
> Jens> Yep
> 
> I hate it too. But the reason it's assumed on is that there is
> essentially no heuristic that works. Just like we assume that READ
> always works.
> 
> Out of the ~200 devices I have access to in the lab:
> 
>  - 100% of the SAS/FC disk drives and SSDs support WRITE SAME
>  - Only 2 out of about 50 different drive models support RSOC
>  - About half of the arrays support WRITE SAME(10/16)
>  - None of the arrays I have support RSOC
> 
> So even if we were to entertain using RSOC for "enterprise" transport
> classes (which I concur would be nice for other reasons), it wouldn't
> solve the WRITE SAME problem...

We're at (almost) -rc7 time, we have to do more than hand wave about
this. What's the plan for 4.10 final?


-- 
Jens Axboe