Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752474AbbEDHry (ORCPT ); Mon, 4 May 2015 03:47:54 -0400 Received: from mail-pa0-f52.google.com ([209.85.220.52]:35786 "EHLO mail-pa0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752380AbbEDHrm (ORCPT ); Mon, 4 May 2015 03:47:42 -0400 Message-ID: <5547241B.1040903@kernel.org> Date: Mon, 04 May 2015 00:47:39 -0700 From: Ming Lin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: NeilBrown CC: linux-kernel@vger.kernel.org, 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" Subject: Re: [PATCH 07/10] block: kill merge_bvec_fn() completely References: <1430203717-13307-1-git-send-email-mlin@kernel.org> <1430203717-13307-8-git-send-email-mlin@kernel.org> <20150429080919.342fddfd@notabene.brown> In-Reply-To: <20150429080919.342fddfd@notabene.brown> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3174 Lines: 96 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? 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/