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From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Jens Axboe <axboe@kernel.dk>
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>,
	"Martin K. Petersen" <martin.petersen@oracle.com>
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, 03 Feb 2017 17:45:25 -0500	[thread overview]
Message-ID: <yq1wpd6vqpm.fsf@oracle.com> (raw)
In-Reply-To: <1e819f0d-ecdc-e54a-bd3d-17de2f71c8a7@kernel.dk> (Jens Axboe's message of "Fri, 3 Feb 2017 09:14:11 -0700")

>>>>> "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...

-- 
Martin K. Petersen	Oracle Linux Engineering

WARNING: multiple messages have this Message-ID (diff)
From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Jens Axboe <axboe@kernel.dk>
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>,
	"Martin K. Petersen" <martin.petersen@oracle.com>
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, 03 Feb 2017 17:45:25 -0500	[thread overview]
Message-ID: <yq1wpd6vqpm.fsf@oracle.com> (raw)
In-Reply-To: <1e819f0d-ecdc-e54a-bd3d-17de2f71c8a7@kernel.dk> (Jens Axboe's message of "Fri, 3 Feb 2017 09:14:11 -0700")

>>>>> "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...

-- 
Martin K. Petersen	Oracle Linux Engineering

  reply	other threads:[~2017-02-03 22:45 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-02-03  7:55 [REGRESSION v4.10-rc1] blkdev_issue_zeroout() returns -EREMOTEIO on the first call for SCSI device that doesn't support WRITE SAME Junichi Nomura
2017-02-03 15:21 ` Jens Axboe
2017-02-03 16:12   ` Christoph Hellwig
2017-02-03 16:14     ` Jens Axboe
2017-02-03 22:45       ` Martin K. Petersen [this message]
2017-02-03 22:45         ` Martin K. Petersen
2017-02-04  3:17         ` Jens Axboe
2017-02-04  8:48           ` Christoph Hellwig

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