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From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Christoph Hellwig <hch@lst.de>
Cc: axboe@kernel.dk, martin.petersen@oracle.com,
	philipp.reisner@linbit.com, lars.ellenberg@linbit.com,
	target-devel@vger.kernel.org, linux-block@vger.kernel.org,
	linux-scsi@vger.kernel.org, drbd-dev@lists.linbit.com,
	dm-devel@redhat.com
Subject: Re: remove REQ_OP_WRITE_SAME
Date: Thu, 13 Apr 2017 22:23:10 -0400	[thread overview]
Message-ID: <yq1mvbjwwvl.fsf@oracle.com> (raw)
In-Reply-To: <20170412084809.8245-1-hch@lst.de> (Christoph Hellwig's message of "Wed, 12 Apr 2017 10:48:01 +0200")


Christoph,

> Now that we are using REQ_OP_WRITE_ZEROES for all zeroing needs in the
> kernel there is very little use left for REQ_OP_WRITE_SAME.  We only
> have two callers left, and both just export optional protocol features
> to remote systems: DRBD and the target code.

While I'm not particularly married to WRITE SAME, I do think it's a
shame that the RAID5/6 code never started using it. It does make a
difference when initializing RAID sets.

The other thing that keeps me a bit on the fence is that a bunch of the
plumbing to handle a bio with a payload different from bi_size is needed
for the copy offload token. I'm hoping to have those patches ready for
4.13. Right now there are a bunch of places where handling of
REQ_OP_COPY_IN and REQ_OP_COPY_OUT share conditionals with WRITE SAME.

So I suggest postponing the decision about whether to rip out WRITE SAME
until I finish the token stuff.

-- 
Martin K. Petersen	Oracle Linux Engineering

WARNING: multiple messages have this Message-ID (diff)
From: "Martin K. Petersen" <martin.petersen-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
To: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Cc: axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org,
	linux-scsi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	martin.petersen-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org,
	philipp.reisner-63ez5xqkn6DQT0dZR+AlfA@public.gmane.org,
	linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
	target-devel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	lars.ellenberg-63ez5xqkn6DQT0dZR+AlfA@public.gmane.org,
	drbd-dev-cunTk1MwBs8qoQakbn7OcQ@public.gmane.org
Subject: Re: remove REQ_OP_WRITE_SAME
Date: Thu, 13 Apr 2017 22:23:10 -0400	[thread overview]
Message-ID: <yq1mvbjwwvl.fsf@oracle.com> (raw)
In-Reply-To: <20170412084809.8245-1-hch-jcswGhMUV9g@public.gmane.org> (Christoph Hellwig's message of "Wed, 12 Apr 2017 10:48:01 +0200")


Christoph,

> Now that we are using REQ_OP_WRITE_ZEROES for all zeroing needs in the
> kernel there is very little use left for REQ_OP_WRITE_SAME.  We only
> have two callers left, and both just export optional protocol features
> to remote systems: DRBD and the target code.

While I'm not particularly married to WRITE SAME, I do think it's a
shame that the RAID5/6 code never started using it. It does make a
difference when initializing RAID sets.

The other thing that keeps me a bit on the fence is that a bunch of the
plumbing to handle a bio with a payload different from bi_size is needed
for the copy offload token. I'm hoping to have those patches ready for
4.13. Right now there are a bunch of places where handling of
REQ_OP_COPY_IN and REQ_OP_COPY_OUT share conditionals with WRITE SAME.

So I suggest postponing the decision about whether to rip out WRITE SAME
until I finish the token stuff.

-- 
Martin K. Petersen	Oracle Linux Engineering

  parent reply	other threads:[~2017-04-14  2:23 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-12  8:48 remove REQ_OP_WRITE_SAME Christoph Hellwig
2017-04-12  8:48 ` Christoph Hellwig
2017-04-12  8:48 ` [PATCH 1/8] drbd: drop REQ_OP_WRITE_SAME support Christoph Hellwig
2017-04-12  8:48 ` [PATCH 2/8] target/iblock: convert WRITE_SAME to blkdev_issue_zeroout Christoph Hellwig
2017-04-12  8:48   ` Christoph Hellwig
2017-04-12  8:48 ` [PATCH 3/8] sd: remove write same support Christoph Hellwig
2017-04-12  8:48   ` Christoph Hellwig
2017-04-12  8:48 ` [PATCH 4/8] md: drop WRITE_SAME support Christoph Hellwig
2017-04-12  8:48 ` [PATCH 5/8] dm: remove write same support Christoph Hellwig
2017-04-12  8:48 ` [PATCH 6/8] block: remove REQ_OP_WRITE_SAME support Christoph Hellwig
2017-04-12  8:48 ` [PATCH 7/8] block: remove bio_no_advance_iter Christoph Hellwig
2017-04-12  8:48 ` [PATCH 8/8] block: use bio_has_data to check if a bio has bvecs Christoph Hellwig
2017-04-14  2:23 ` Martin K. Petersen [this message]
2017-04-14  2:23   ` remove REQ_OP_WRITE_SAME Martin K. Petersen
2017-05-05  8:57   ` Christoph Hellwig
2017-05-05  8:57     ` Christoph Hellwig
2017-05-09  2:06     ` Martin K. Petersen
2017-05-09  2:06       ` Martin K. Petersen

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