Re: [PATCH v5 01/11] block: make generic_make_request handle arbitrarily sized bios

From: Ming Lin <mlin@kernel.org>
To: Mike Snitzer <snitzer@redhat.com>
Cc: axboe@fb.com, Christoph Hellwig <hch@infradead.org>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	device-mapper development <dm-devel@redhat.com>,
	Ming Lei <ming.lei@canonical.com>, Christoph Hellwig <hch@lst.de>,
	Alasdair Kergon <agk@redhat.com>,
	Lars Ellenberg <drbd-dev@lists.linbit.com>,
	Philip Kelleher <pjk1939@linux.vnet.ibm.com>,
	Kent Overstreet <kent.overstreet@gmail.com>,
	Nitin Gupta <ngupta@vflare.org>,
	Ming Lin <ming.l@ssi.samsung.com>,
	Oleg Drokin <oleg.drokin@intel.com>,
	Al Viro <viro@zeniv.linux.org.uk>, Jens Axboe <axboe@kernel.dk>,
	Andreas Dilger <andreas.dilger@intel.com>,
	Geoff Levand <geoff@infradead.org>, Jiri Kosina <jkosina@suse.cz>,
	lkml <linux-kernel@vger.kernel.org>, Jim Paris <jim@jtan.com>,
	Minchan Kim <minchan@kernel.org>, Dongsu Park <dpark@posteo.net>,
	drbd-user@lists.linbit.com, Joe Thornber <ejt@redhat.com>
Subject: Re: [PATCH v5 01/11] block: make generic_make_request handle arbitrarily sized bios
Date: Mon, 10 Aug 2015 09:14:12 -0700	[thread overview]
Message-ID: <1439223252.27204.10.camel@hasee> (raw)
In-Reply-To: <20150810150216.GA22719@redhat.com>

On Mon, 2015-08-10 at 11:02 -0400, Mike Snitzer wrote:
> On Sun, Aug 09 2015 at  3:18am -0400,
> Ming Lin <mlin@kernel.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)

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@redhat.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.