Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755516AbbEFHKf (ORCPT ); Wed, 6 May 2015 03:10:35 -0400 Received: from mail.kernel.org ([198.145.29.136]:33479 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755481AbbEFHK3 (ORCPT ); Wed, 6 May 2015 03:10:29 -0400 MIME-Version: 1.0 In-Reply-To: <5547241B.1040903@kernel.org> References: <1430203717-13307-1-git-send-email-mlin@kernel.org> <1430203717-13307-8-git-send-email-mlin@kernel.org> <20150429080919.342fddfd@notabene.brown> <5547241B.1040903@kernel.org> Date: Wed, 6 May 2015 00:10:24 -0700 Message-ID: Subject: Re: [PATCH 07/10] block: kill merge_bvec_fn() completely From: Ming Lin To: Ming Lin Cc: NeilBrown , lkml , Christoph Hellwig , Jens Axboe , Kent Overstreet , Dongsu Park , Lars Ellenberg , drbd-user@lists.linbit.com, Jiri Kosina , Yehuda Sadeh , Sage Weil , Alex Elder , ceph-devel@vger.kernel.org, Alasdair Kergon , Mike Snitzer , dm-devel@redhat.com, linux-raid@vger.kernel.org, Christoph Hellwig , "Martin K. Petersen" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3924 Lines: 105 On Mon, May 4, 2015 at 12:47 AM, Ming Lin wrote: > On 04/28/2015 03:09 PM, NeilBrown wrote: >> On Mon, 27 Apr 2015 23:48:34 -0700 Ming Lin wrote: >> >>> From: Kent Overstreet >>> >>> As generic_make_request() is now able to handle arbitrarily sized bios, >>> it's no longer necessary for each individual block driver to define its >>> own ->merge_bvec_fn() callback. Remove every invocation completely. >> >> This patch it just a little premature I think. >> >> md/raid5 still assumes read requests will mostly fit within a single chunk >> (which merge_bvec_fn encourages) so they can be serviced without using the >> stripe-cache. >> You've just broken that assumption. >> >> I think 'chunk_aligned_read' needs to get a loop using bio_split, a bit like >> raid0, first. > > How about below? Hi NeilBrown, Are you OK with below fix? Then I'll include it in the next version. Thanks. > > drivers/md/raid5.c | 35 ++++++++++++++++++++++++++++++++--- > 1 file changed, 32 insertions(+), 3 deletions(-) > > diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c > index e42b624..2ddfa1e 100644 > --- a/drivers/md/raid5.c > +++ b/drivers/md/raid5.c > @@ -4709,7 +4709,7 @@ static void raid5_align_endio(struct bio *bi, int error) > add_bio_to_retry(raid_bi, conf); > } > > -static int chunk_aligned_read(struct mddev *mddev, struct bio * raid_bio) > +static int __chunk_aligned_read(struct mddev *mddev, struct bio *raid_bio) > { > struct r5conf *conf = mddev->private; > int dd_idx; > @@ -4718,7 +4718,7 @@ static int chunk_aligned_read(struct mddev *mddev, struct bio * raid_bio) > sector_t end_sector; > > if (!in_chunk_boundary(mddev, raid_bio)) { > - pr_debug("chunk_aligned_read : non aligned\n"); > + pr_debug("__chunk_aligned_read : non aligned\n"); > return 0; > } > /* > @@ -4793,6 +4793,35 @@ static int chunk_aligned_read(struct mddev *mddev, struct bio * raid_bio) > } > } > > +static struct bio *chunk_aligned_read(struct mddev *mddev, struct bio *raid_bio) > +{ > + struct bio *split; > + > + do { > + sector_t sector = raid_bio->bi_iter.bi_sector; > + unsigned chunk_sects = mddev->chunk_sectors; > + > + unsigned sectors = chunk_sects - > + (likely(is_power_of_2(chunk_sects)) > + ? (sector & (chunk_sects-1)) > + : sector_div(sector, chunk_sects)); > + > + if (sectors < bio_sectors(raid_bio)) { > + split = bio_split(raid_bio, sectors, GFP_NOIO, fs_bio_set); > + bio_chain(split, raid_bio); > + } else > + split = raid_bio; > + > + if (!__chunk_aligned_read(mddev, split)) { > + if (split != raid_bio) > + generic_make_request(raid_bio); > + return split; > + } > + } while (split != raid_bio); > + > + return NULL; > +} > + > /* __get_priority_stripe - get the next stripe to process > * > * Full stripe writes are allowed to pass preread active stripes up until > @@ -5071,7 +5100,7 @@ static void make_request(struct mddev *mddev, struct bio * bi) > */ > if (rw == READ && mddev->degraded == 0 && > mddev->reshape_position == MaxSector && > - chunk_aligned_read(mddev,bi)) > + (!(bi = chunk_aligned_read(mddev, bi)))) > return; > > if (unlikely(bi->bi_rw & REQ_DISCARD)) { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/