From: Ming Lin <mlin@kernel.org>
To: Mike Snitzer <snitzer@redhat.com>
Cc: Jeff Moyer <jmoyer@redhat.com>,
Christoph Hellwig <hch@infradead.org>,
lkml <linux-kernel@vger.kernel.org>, Jens Axboe <axboe@kernel.dk>,
Kent Overstreet <kent.overstreet@gmail.com>,
Dongsu Park <dpark@posteo.net>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
Ming Lin <ming.l@ssi.samsung.com>,
linux-nvme@lists.infradead.org
Subject: Re: [PATCH v6 05/11] block: remove split code in blkdev_issue_{discard,write_same}
Date: Wed, 21 Oct 2015 10:18:22 -0700 [thread overview]
Message-ID: <1445447902.26847.3.camel@ssi> (raw)
In-Reply-To: <20151021153351.GA4984@redhat.com>
On Wed, 2015-10-21 at 11:33 -0400, Mike Snitzer wrote:
> On Wed, Oct 21 2015 at 11:01am -0400,
> Ming Lin <mlin@kernel.org> wrote:
>
> > On Wed, 2015-10-21 at 09:39 -0400, Jeff Moyer wrote:
> > > Christoph Hellwig <hch@infradead.org> writes:
> > >
> > > > Jens, Ming:
> > > >
> > > > are you fine with the one liner change to get back to the old I/O
> > > > pattern? While it looks like the cards fault I'd like to avoid this
> > > > annoying regression.
> > >
> > > I'm not Jens or Ming, but your patch looks fine to me, though you'll
> > > want to remove the MAX_BIO_SECTORS definition since it's now unused.
> > > It's not clear to me why the limit was lowered in the first place.
> >
> > UINT_MAX >> 9 is not power of 2 and it causes dm-thinp discard fails.
> >
> > At the lengthy discussion:
> > [PATCH v5 01/11] block: make generic_make_request handle arbitrarily sized bios
> > We agreed to cap discard to 2G as an interim solution for 4.3 until the
> > dm-thinp discard code is rewritten.
>
> But did Jens ever commit that change to cap at 2G? I don't recall
> seeing it.
Yes, commit b49a0871
>
> > Hi Mike,
> >
> > Will the dm-thinp discard rewritten ready for 4.4?
>
> No. I'm not clear what needs changing in dm-thinp. I'll have to
> revisit the thread to refresh my memory.
>
> BTW, DM thinp can easily handle discards that aren't a power-of-2 so
> long as the requested discard is a factor of the thinp blocksize.
You are right. It's not about power-of-2.
Copy my old post here about why dm-thinp discard may fail with "UINT_MAX
>> 9".
4G: 8388608 sectors
UINT_MAX: 8388607 sectors
dm-thinp block size = default discard granularity = 128 sectors
blkdev_issue_discard(sector=0, nr_sectors=8388608)
[start_sector, end_sector]
[0, 8388607]
[0, 8388606], then dm-thinp splits it to 2 bios
[0, 8388479]
[8388480, 8388606] ---> this has problem in process_discard_bio(),
because the discard size(7 sectors) covers less than a block(128 sectors)
[8388607, 8388607] ---> same problem
next prev parent reply other threads:[~2015-10-21 17:18 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-12 7:07 [PATCH v6 00/11] simplify block layer based on immutable biovecs Ming Lin
2015-08-12 7:07 ` [PATCH v6 01/11] block: make generic_make_request handle arbitrarily sized bios Ming Lin
2015-08-12 7:07 ` [PATCH v6 02/11] block: simplify bio_add_page() Ming Lin
2015-08-12 7:07 ` [PATCH v6 03/11] bcache: remove driver private bio splitting code Ming Lin
2016-01-08 1:53 ` Eric Wheeler
2015-08-12 7:07 ` [PATCH v6 04/11] btrfs: remove bio splitting and merge_bvec_fn() calls Ming Lin
2015-08-12 7:07 ` [PATCH v6 05/11] block: remove split code in blkdev_issue_{discard,write_same} Ming Lin
2015-10-13 11:50 ` Christoph Hellwig
2015-10-13 17:44 ` Ming Lin
2015-10-14 13:27 ` Christoph Hellwig
2015-10-14 16:38 ` [PATCH v6 05/11] block: remove split code in blkdev_issue_{discard,write_same}B Keith Busch
2015-10-14 16:50 ` Christoph Hellwig
2015-10-21 16:02 ` [PATCH v6 05/11] block: remove split code in blkdev_issue_{discard,write_same} Mike Snitzer
2015-10-21 16:19 ` Mike Snitzer
2015-10-21 16:33 ` Martin K. Petersen
2015-10-21 17:33 ` Ming Lin
2015-10-21 18:18 ` Mike Snitzer
2015-10-21 20:13 ` Ming Lin
2015-10-22 10:24 ` Christoph Hellwig
2015-10-22 11:22 ` Christoph Hellwig
2015-10-21 7:21 ` Christoph Hellwig
2015-10-21 13:39 ` Jeff Moyer
2015-10-21 15:01 ` Ming Lin
2015-10-21 15:33 ` Mike Snitzer
2015-10-21 17:18 ` Ming Lin [this message]
2015-08-12 7:07 ` [PATCH v6 06/11] md/raid5: split bio for chunk_aligned_read Ming Lin
2015-08-12 7:07 ` [PATCH v6 07/11] md/raid5: get rid of bio_fits_rdev() Ming Lin
2015-08-12 7:07 ` [PATCH v6 08/11] block: kill merge_bvec_fn() completely Ming Lin
2015-08-12 7:07 ` [PATCH v6 09/11] fs: use helper bio_add_page() instead of open coding on bi_io_vec Ming Lin
2015-08-12 7:07 ` [PATCH v6 10/11] block: remove bio_get_nr_vecs() Ming Lin
2015-08-12 7:07 ` [PATCH v6 11/11] Documentation: update notes in biovecs about arbitrarily sized bios Ming Lin
2015-08-13 16:51 ` [PATCH v6 00/11] simplify block layer based on immutable biovecs Jens Axboe
2015-08-13 17:03 ` Ming Lin
2015-08-13 17:07 ` Jens Axboe
2015-08-13 17:36 ` Ming Lin
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