Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752613AbbEHF6D (ORCPT ); Fri, 8 May 2015 01:58:03 -0400 Received: from mail-pd0-f180.google.com ([209.85.192.180]:33609 "EHLO mail-pd0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752178AbbEHF55 (ORCPT ); Fri, 8 May 2015 01:57:57 -0400 Message-ID: <554C5062.5060107@kernel.org> Date: Thu, 07 May 2015 22:57:54 -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 , linux-raid@vger.kernel.org Subject: Re: [PATCH v3 07/11] md/raid5: split bio for chunk_aligned_read References: <1430980461-5235-1-git-send-email-mlin@kernel.org> <1430980461-5235-8-git-send-email-mlin@kernel.org> <20150508141435.17666f2a@notabene.brown> In-Reply-To: <20150508141435.17666f2a@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: 5918 Lines: 171 On 05/07/2015 09:14 PM, NeilBrown wrote: > On Wed, 6 May 2015 23:34:17 -0700 Ming Lin wrote: > >> If a read request fits entirely in a chunk, it will be passed directly to the >> underlying device (providing it hasn't failed of course). If it doesn't fit, >> the slightly less efficient path that uses the stripe_cache is used. >> Requests that get to the stripe cache are always completely split up as >> necessary. >> >> So with RAID5, ripping out the merge_bvec_fn doesn't cause it to stop work, >> but could cause it to take the less efficient path more often. >> >> All that is needed to manage this is for 'chunk_aligned_read' do some bio >> splitting, much like the RAID0 code does. >> >> Cc: Neil Brown >> Cc: linux-raid@vger.kernel.org >> Signed-off-by: Ming Lin >> --- >> drivers/md/raid5.c | 42 +++++++++++++++++++++++++++++++++++++----- >> 1 file changed, 37 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c >> index 7f4a717..b18f548 100644 >> --- a/drivers/md/raid5.c >> +++ b/drivers/md/raid5.c >> @@ -4738,7 +4738,7 @@ 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 raid5_read_one_chunk(struct mddev *mddev, struct bio *raid_bio) >> { >> struct r5conf *conf = mddev->private; >> int dd_idx; >> @@ -4747,7 +4747,7 @@ 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("%s: non aligned\n", __func__); >> return 0; >> } >> /* >> @@ -4822,6 +4822,36 @@ 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; >> + >> + if (likely(is_power_of_2(chunk_sects))) >> + sectors = chunk_sects - (sector & (chunk_sects-1)); >> + else >> + sectors = chunk_sects - sector_div(sector, chunk_sects); > > RAID5 doesn't currently allow non-power-of-2 chunks. So this test is > pointless, but not really harmful. Maybe someday we will. > > I'm equally happy for it to stay or go. Then it's better for it to go. Thanks. >From d40e9dfaae261cc86170193305e2022d2e1cda1a Mon Sep 17 00:00:00 2001 From: Ming Lin Date: Wed, 6 May 2015 22:51:24 -0700 Subject: [PATCH 07/11] md/raid5: split bio for chunk_aligned_read If a read request fits entirely in a chunk, it will be passed directly to the underlying device (providing it hasn't failed of course). If it doesn't fit, the slightly less efficient path that uses the stripe_cache is used. Requests that get to the stripe cache are always completely split up as necessary. So with RAID5, ripping out the merge_bvec_fn doesn't cause it to stop work, but could cause it to take the less efficient path more often. All that is needed to manage this is for 'chunk_aligned_read' do some bio splitting, much like the RAID0 code does. Cc: Neil Brown Cc: linux-raid@vger.kernel.org Acked-by: NeilBrown Signed-off-by: Ming Lin --- drivers/md/raid5.c | 37 ++++++++++++++++++++++++++++++++----- 1 file changed, 32 insertions(+), 5 deletions(-) diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 7f4a717..1978aa9 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -4738,7 +4738,7 @@ 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 raid5_read_one_chunk(struct mddev *mddev, struct bio *raid_bio) { struct r5conf *conf = mddev->private; int dd_idx; @@ -4747,7 +4747,7 @@ 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("%s: non aligned\n", __func__); return 0; } /* @@ -4822,6 +4822,31 @@ 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 - (sector & (chunk_sects-1)); + + 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 (!raid5_read_one_chunk(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 @@ -5099,9 +5124,11 @@ static void make_request(struct mddev *mddev, struct bio * bi) * data on failed drives. */ if (rw == READ && mddev->degraded == 0 && - mddev->reshape_position == MaxSector && - chunk_aligned_read(mddev,bi)) - return; + mddev->reshape_position == MaxSector) { + bi = chunk_aligned_read(mddev, bi); + if (!bi) + return; + } if (unlikely(bi->bi_rw & REQ_DISCARD)) { make_discard_request(mddev, bi); -- 1.9.1 -- 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/