linux-kernel - Re: [PATCH v5 01/11] block: make generic_make

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Date:	Mon, 10 Aug 2015 09:18:38 -0700
From:	Ming Lin <mlin@...nel.org>
To:	Mike Snitzer <snitzer@...hat.com>
Cc:	axboe@...com, Christoph Hellwig <hch@...radead.org>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	device-mapper development <dm-devel@...hat.com>,
	Ming Lei <ming.lei@...onical.com>,
	Christoph Hellwig <hch@....de>,
	Alasdair Kergon <agk@...hat.com>,
	Lars Ellenberg <drbd-dev@...ts.linbit.com>,
	Philip Kelleher <pjk1939@...ux.vnet.ibm.com>,
	Kent Overstreet <kent.overstreet@...il.com>,
	Nitin Gupta <ngupta@...are.org>,
	Ming Lin <ming.l@....samsung.com>,
	Oleg Drokin <oleg.drokin@...el.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Jens Axboe <axboe@...nel.dk>,
	Andreas Dilger <andreas.dilger@...el.com>,
	Geoff Levand <geoff@...radead.org>,
	Jiri Kosina <jkosina@...e.cz>,
	lkml <linux-kernel@...r.kernel.org>, Jim Paris <jim@...n.com>,
	Minchan Kim <minchan@...nel.org>,
	Dongsu Park <dpark@...teo.net>, drbd-user@...ts.linbit.com,
	Joe Thornber <ejt@...hat.com>
Subject: Re: [PATCH v5 01/11] block: make generic_make_request handle
 arbitrarily sized bios

On Mon, 2015-08-10 at 09:14 -0700, Ming Lin wrote:
> On Mon, 2015-08-10 at 11:02 -0400, Mike Snitzer wrote:
> > On Sun, Aug 09 2015 at  3:18am -0400,
> > Ming Lin <mlin@...nel.org> wrote:
> > 
> > > On Sun, 2015-08-09 at 00:01 -0700, Christoph Hellwig wrote:
> > > > On Sat, Aug 08, 2015 at 11:55:47PM -0700, Ming Lin wrote:
> > > > > Will change it to MAX_BIO_SECTORS.
> > > > > May I add your ACK?
> > > > 
> > > > Yes, please go ahead.
> > > 
> > > Thanks. I'll send a new version of the series once device-mapper guy
> > > acks.
> > > 
> > > Hi Mike,
> > > 
> > > I have updated my tree. Could you pull and re-test?
> > > https://git.kernel.org/cgit/linux/kernel/git/mlin/linux.git/log/?h=block-generic-req
> > > 
> > > The 2 thin-provisioning tests passed.
> > 
> > I've merged your latest branch with my dm-4.3 branch, I had one conflict
> > in the merge due to the dm_merge_bvec() change from 4.2-rc6 (no
> > surprise).  I've published the result here:
> > http://git.kernel.org/cgit/linux/kernel/git/snitzer/linux.git/log/?h=block-late-bio-splitting
> > 
> > It passes the device-mapper-test-suite's 'thin-provisioning' tests.
> > 
> > > Hope I can have your ACK soon.
> > 
> > Shouldn't we also be using MAX_BIO_SECTORS in blkdev_issue_write_same
> > (instead of UINT_MAX >> 9)?
> 
> I also prefer using MAX_BIO_SECTORS.
> Otherwise, we may have non page size aligned splits.
> 
> Say, write_same 8G.
> 
> Using UINT_MAX >> 9, we'll have 2 sector aligned splits in
> blkdev_issue_write_same():
> 0 - (4G - 512 - 1)
> (4G - 512, 8G -1)

Actually, 3 sector aligned splits.

0 - (4G-512-1)
(4G-512), (8G-512-1)
(8G-512), (8G-1)

> 
> This looks weired.
> 
> Using MAX_BIO_SECTORS, we'll have 4 page size aligned splits:
> 0 - (2G -1)
> 2G - (4G - 1)
> 4G - (6G - 1)
> 6G - (8G - 1)
> 
> I'll use MAX_BIO_SECTORS in blkdev_issue_write_same() if no objection.
> 
> > 
> > Aside from that, I'm in favor of seeing this late bio splitting patchset
> > finally land upstream (hopefully in time for the 4.3 merge, Jens?):
> > 
> > Acked-by: Mike Snitzer <snitzer@...hat.com>
> 
> Thanks!
> 
> May I add your Ack to "PATCH: block: kill merge_bvec_fn() completely"
> also?
> 
> > 
> > p.s. I'll be working with Joe Thornber on optimizing DM (particularly
> > dm-thinp and dm-cache) once this patchset is included upstream.  You'll
> > see I've already added a couple WIP dm-thinp patches ontop.
> 


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