From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Bart Van Assche <Bart.VanAssche@sandisk.com>
Cc: "agk\@redhat.com" <agk@redhat.com>,
"lars.ellenberg\@linbit.com" <lars.ellenberg@linbit.com>,
"snitzer\@redhat.com" <snitzer@redhat.com>,
"hch\@lst.de" <hch@lst.de>,
"martin.petersen\@oracle.com" <martin.petersen@oracle.com>,
"philipp.reisner\@linbit.com" <philipp.reisner@linbit.com>,
"axboe\@kernel.dk" <axboe@kernel.dk>,
"shli\@kernel.org" <shli@kernel.org>,
"linux-scsi\@vger.kernel.org" <linux-scsi@vger.kernel.org>,
"dm-devel\@redhat.com" <dm-devel@redhat.com>,
"drbd-dev\@lists.linbit.com" <drbd-dev@lists.linbit.com>,
"linux-block\@vger.kernel.org" <linux-block@vger.kernel.org>,
"linux-raid\@vger.kernel.org" <linux-raid@vger.kernel.org>
Subject: Re: [PATCH 03/23] sd: implement REQ_OP_WRITE_ZEROES
Date: Wed, 29 Mar 2017 22:25:33 -0400 [thread overview]
Message-ID: <yq1o9wj4i1u.fsf@oracle.com> (raw)
In-Reply-To: <1490726988.2573.16.camel@sandisk.com> (Bart Van Assche's message of "Tue, 28 Mar 2017 18:50:01 +0000")
Bart Van Assche <Bart.VanAssche@sandisk.com> writes:
Hi Bart,
> A quote from SBC: "An OPTIMAL UNMAP GRANULARITY field set to a
> non-zero value indicates the optimal granularity in logical blocks for
> unmap requests (e.g., an UNMAP command or a WRITE SAME (16) command
> with the UNMAP bit set to one). An unmap request with a number of
> logical blocks that is not a multiple of this value may result in
> unmap operations on fewer LBAs than requested."
Indeed. Fewer LBAs than requested may be *unmapped*. That does not imply
that they are not *written*.
> This means that just like the start and end of a discard must be
> aligned on a discard_granularity boundary, WRITE SAME commands with
> the UNMAP bit set must also respect that granularity. I think this
> means that either __blkdev_issue_zeroout() has to be modified such
> that it rejects unaligned REQ_OP_WRITE_ZEROES operations or that
> blk_bio_write_same_split() has to be modified such that it generates
> REQ_OP_WRITEs for the unaligned start and tail.
No, that's not correct. SBC states:
"a) if the Data-Out Buffer of the WRITE SAME command is the same as the
logical block data returned by a read operation from that LBA while
in the unmapped state, then:
1) the device server performs the actions described in table 6
[unmap]; and
2) if an unmap operation is not performed in step 1), then the device
server shall perform the specified write operation to that LBA;"
I.e. With WRITE SAME it is the responsibility of the device server to
write any LBAs described by the command that were not successfully
unmapped.
--
Martin K. Petersen Oracle Linux Engineering
next prev parent reply other threads:[~2017-03-30 2:25 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-23 14:33 RFC: always use REQ_OP_WRITE_ZEROES for zeroing offload Christoph Hellwig
2017-03-23 14:33 ` [PATCH 01/23] block: renumber REQ_OP_WRITE_ZEROES Christoph Hellwig
2017-03-28 16:12 ` Bart Van Assche
2017-03-30 8:53 ` hch
2017-03-23 14:33 ` [PATCH 02/23] block: implement splitting of REQ_OP_WRITE_ZEROES bios Christoph Hellwig
2017-03-23 14:33 ` [PATCH 03/23] sd: implement REQ_OP_WRITE_ZEROES Christoph Hellwig
2017-03-28 18:50 ` Bart Van Assche
2017-03-28 19:33 ` Mike Snitzer
2017-03-29 14:51 ` Paolo Bonzini
2017-03-29 16:28 ` Bart Van Assche
2017-03-29 16:53 ` Paolo Bonzini
2017-03-30 2:25 ` Martin K. Petersen [this message]
2017-03-23 14:33 ` [PATCH 04/23] md: support REQ_OP_WRITE_ZEROES Christoph Hellwig
2017-03-23 14:33 ` [PATCH 05/23] dm: " Christoph Hellwig
2017-03-23 14:33 ` [PATCH 06/23] dm-kcopyd: switch to use REQ_OP_WRITE_ZEROES Christoph Hellwig
2017-03-23 14:55 ` Mike Snitzer
2017-03-23 14:56 ` Christoph Hellwig
2017-03-23 15:10 ` Mike Snitzer
2017-03-27 9:12 ` Christoph Hellwig
2017-03-23 14:33 ` [PATCH 07/23] block: stop using blkdev_issue_write_same for zeroing Christoph Hellwig
2017-03-23 14:33 ` [PATCH 08/23] block: add a flags argument to (__)blkdev_issue_zeroout Christoph Hellwig
2017-03-23 14:33 ` [PATCH 09/23] block: add a REQ_UNMAP flag for REQ_OP_WRITE_ZEROES Christoph Hellwig
2017-03-23 14:33 ` [PATCH 10/23] block: add a new BLKDEV_ZERO_NOFALLBACK flag Christoph Hellwig
2017-03-23 14:33 ` [PATCH 11/23] block_dev: use blkdev_issue_zerout for hole punches Christoph Hellwig
2017-03-28 16:50 ` Bart Van Assche
2017-03-30 8:59 ` hch
2017-03-23 14:33 ` [PATCH 12/23] sd: handle REQ_UNMAP Christoph Hellwig
2017-03-28 16:48 ` Bart Van Assche
2017-03-29 14:57 ` Paolo Bonzini
2017-03-30 9:02 ` hch
2017-03-30 15:28 ` Martin K. Petersen
2017-03-30 17:30 ` hch
2017-03-31 2:19 ` Martin K. Petersen
2017-03-31 7:18 ` hch
2017-03-23 14:33 ` [PATCH 13/23] nvme: implement REQ_OP_WRITE_ZEROES Christoph Hellwig
2017-03-23 14:33 ` [PATCH 14/23] zram: " Christoph Hellwig
2017-03-23 14:33 ` [PATCH 15/23] loop: " Christoph Hellwig
2017-03-23 14:33 ` [PATCH 16/23] brd: remove discard support Christoph Hellwig
2017-03-23 14:33 ` [PATCH 17/23] rbd: remove the discard_zeroes_data flag Christoph Hellwig
2017-03-23 14:33 ` [PATCH 18/23] rsxx: " Christoph Hellwig
2017-03-23 14:33 ` [PATCH 19/23] mmc: " Christoph Hellwig
2017-03-23 14:33 ` [PATCH 20/23] block: stop using discards for zeroing Christoph Hellwig
2017-03-23 14:33 ` [PATCH 21/23] drbd: make intelligent use of blkdev_issue_zeroout Christoph Hellwig
2017-03-23 14:33 ` [PATCH 22/23] drbd: implement REQ_OP_WRITE_ZEROES Christoph Hellwig
2017-03-30 10:06 ` Lars Ellenberg
2017-03-30 11:44 ` Christoph Hellwig
2017-03-30 12:50 ` [Drbd-dev] " Lars Ellenberg
2017-03-30 13:49 ` Mike Snitzer
2017-03-30 15:20 ` Martin K. Petersen
2017-03-30 23:15 ` Mike Snitzer
2017-03-31 2:34 ` Martin K. Petersen
2017-03-31 7:17 ` Christoph Hellwig
2017-03-23 14:33 ` [PATCH 23/23] block: remove the discard_zeroes_data flag Christoph Hellwig
2017-03-28 17:00 ` Bart Van Assche
2017-03-29 14:52 ` Paolo Bonzini
2017-03-30 9:06 ` hch
2017-03-30 15:29 ` Martin K. Petersen
2017-03-30 17:29 ` hch
2017-03-23 15:54 ` RFC: always use REQ_OP_WRITE_ZEROES for zeroing offload Lars Ellenberg
2017-03-23 17:02 ` Mike Snitzer
2017-03-23 22:53 ` Lars Ellenberg
2017-03-29 14:57 ` Paolo Bonzini
2017-03-27 9:10 ` Christoph Hellwig
2017-03-27 14:03 ` Mike Snitzer
2017-03-27 14:57 ` Christoph Hellwig
2017-03-27 15:08 ` [Drbd-dev] " Bart Van Assche
2017-03-30 9:04 ` Christoph Hellwig
2017-03-30 15:12 ` Mike Snitzer
2017-03-30 15:22 ` Martin K. Petersen
2017-03-30 15:38 ` Mike Snitzer
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