From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: jiangyiwen <jiangyiwen@huawei.com>
Cc: axboe@kernel.dk, linux-kernel@vger.kernel.org,
dm-devel@redhat.com, martin.petersen@oracle.com,
"Lukáš Czerner" <lczerner@redhat.com>,
xuejiufei@huawei.com, "Qijiang (Joseph,
Euler)" <joseph.qi@huawei.com>
Subject: Re: [dm-devel] [PATCH] block: do not return -EOPNOTSUPP only when issue a discard request
Date: Wed, 03 Feb 2016 17:00:56 -0500 [thread overview]
Message-ID: <yq1egctlahz.fsf@sermon.lab.mkp.net> (raw)
In-Reply-To: <56B1CE5C.10201@huawei.com> (jiangyiwen@huawei.com's message of "Wed, 3 Feb 2016 17:54:36 +0800")
>>>>> "Yiwen" == jiangyiwen <jiangyiwen@huawei.com> writes:
Yiwen> commit 8af1954d172a("blkdev: Do not return -EOPNOTSUPP if discard
Yiwen> is supported") only solve the situation of discard, because When
Yiwen> applications issue a discard request to device, they can't expect
Yiwen> deterministic behaviour. However, WRITE SAME should not ignore
Yiwen> error with EOPNOTSUPP, because if applications issue WRITE SAME
Yiwen> requests to device, it should return deterministic results to
Yiwen> applications according to the T10 standard, or else it will cause
Yiwen> an inconsistent state between upper layer and bottom layer.
Yiwen> So ignoring error with EOPNOTSUPP only in discard situation.
If an underlying device fails a WRITE SAME request, SCSI will not return
EOPNOTSUPP. Instead we will mark 0 bytes of the request as complete and
disable WRITE SAME support on the device. So any EOPNOTSUPP error in
this case would be coming from MD/DM.
That said, I agree with the patch.
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
--
Martin K. Petersen Oracle Linux Engineering
prev parent reply other threads:[~2016-02-03 22:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-03 9:54 [dm-devel] [PATCH] block: do not return -EOPNOTSUPP only when issue a discard request jiangyiwen
2016-02-03 16:19 ` Lukáš Czerner
2016-02-03 22:00 ` Martin K. Petersen [this message]
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