From patchwork Mon Dec 18 12:22:22 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 10119439 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 43D336057F for ; Mon, 18 Dec 2017 12:39:45 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 363E428FD4 for ; Mon, 18 Dec 2017 12:39:45 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 2AC1B28FD6; Mon, 18 Dec 2017 12:39:45 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B995428FD5 for ; Mon, 18 Dec 2017 12:39:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759052AbdLRM21 (ORCPT ); Mon, 18 Dec 2017 07:28:27 -0500 Received: from mx1.redhat.com ([209.132.183.28]:45070 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759046AbdLRM20 (ORCPT ); Mon, 18 Dec 2017 07:28:26 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E4984883BA; Mon, 18 Dec 2017 12:28:25 +0000 (UTC) Received: from localhost (ovpn-12-48.pek2.redhat.com [10.72.12.48]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8C4994F9DA; Mon, 18 Dec 2017 12:28:14 +0000 (UTC) From: Ming Lei To: Jens Axboe , Christoph Hellwig , Alexander Viro , Kent Overstreet Cc: Huang Ying , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Theodore Ts'o , "Darrick J . Wong" , Coly Li , Filipe Manana , Ming Lei Subject: [PATCH V4 20/45] block: use bio_for_each_segment() to compute segments count Date: Mon, 18 Dec 2017 20:22:22 +0800 Message-Id: <20171218122247.3488-21-ming.lei@redhat.com> In-Reply-To: <20171218122247.3488-1-ming.lei@redhat.com> References: <20171218122247.3488-1-ming.lei@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Mon, 18 Dec 2017 12:28:26 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Firstly it is more efficient to use bio_for_each_segment() in both blk_bio_segment_split() and __blk_recalc_rq_segments() to compute how many segments there are in the bio. Secondaly once bio_for_each_segment() is used, the bvec may need to be splitted because its length can be very longer than max segment size, so we have to split the big bvec into several segments. Thirdly during splitting multipage bvec into segments, max segment number may be reached, then the bio need to be splitted when this happens. Signed-off-by: Ming Lei --- block/blk-merge.c | 97 ++++++++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 79 insertions(+), 18 deletions(-) diff --git a/block/blk-merge.c b/block/blk-merge.c index 25ffb84be058..f65546b46fff 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -97,6 +97,62 @@ static inline unsigned get_max_io_size(struct request_queue *q, return sectors; } +/* + * Split the bvec @bv into segments, and update all kinds of + * variables. + */ +static bool bvec_split_segs(struct request_queue *q, struct bio_vec *bv, + unsigned *nsegs, unsigned *last_seg_size, + unsigned *front_seg_size, unsigned *sectors) +{ + bool need_split = false; + unsigned len = bv->bv_len; + unsigned total_len = 0; + unsigned new_nsegs = 0, seg_size = 0; + + if ((*nsegs >= queue_max_segments(q)) || !len) + return need_split; + + /* + * Multipage bvec may be too big to hold in one segment, + * so the current bvec has to be splitted as multiple + * segments. + */ + while (new_nsegs + *nsegs < queue_max_segments(q)) { + seg_size = min(queue_max_segment_size(q), len); + + new_nsegs++; + total_len += seg_size; + len -= seg_size; + + if ((queue_virt_boundary(q) && ((bv->bv_offset + + total_len) & queue_virt_boundary(q))) || !len) + break; + } + + /* split in the middle of the bvec */ + if (len) + need_split = true; + + /* update front segment size */ + if (!*nsegs) { + unsigned first_seg_size = seg_size; + + if (new_nsegs > 1) + first_seg_size = queue_max_segment_size(q); + if (*front_seg_size < first_seg_size) + *front_seg_size = first_seg_size; + } + + /* update other varibles */ + *last_seg_size = seg_size; + *nsegs += new_nsegs; + if (sectors) + *sectors += total_len >> 9; + + return need_split; +} + static struct bio *blk_bio_segment_split(struct request_queue *q, struct bio *bio, struct bio_set *bs, @@ -111,7 +167,7 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, const unsigned max_sectors = get_max_io_size(q, bio); unsigned advance = 0; - bio_for_each_page(bv, bio, iter) { + bio_for_each_segment(bv, bio, iter) { /* * If the queue doesn't support SG gaps and adding this * offset would create a gap, disallow it. @@ -126,8 +182,12 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, */ if (nsegs < queue_max_segments(q) && sectors < max_sectors) { - nsegs++; - sectors = max_sectors; + /* split in the middle of bvec */ + bv.bv_len = (max_sectors - sectors) << 9; + bvec_split_segs(q, &bv, &nsegs, + &seg_size, + &front_seg_size, + §ors); } goto split; } @@ -139,10 +199,9 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, goto new_segment; if (seg_size + bv.bv_len > queue_max_segment_size(q)) { /* - * On assumption is that initial value of - * @seg_size(equals to bv.bv_len) won't be - * bigger than max segment size, but will - * becomes false after multipage bvec comes. + * The initial value of @seg_size won't be + * bigger than max segment size, because we + * split the bvec via bvec_split_segs(). */ advance = queue_max_segment_size(q) - seg_size; @@ -174,11 +233,12 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, if (nsegs == 1 && seg_size > front_seg_size) front_seg_size = seg_size; - nsegs++; bvprv = bv; bvprvp = &bvprv; - seg_size = bv.bv_len; - sectors += bv.bv_len >> 9; + + if (bvec_split_segs(q, &bv, &nsegs, &seg_size, + &front_seg_size, §ors)) + goto split; /* restore the bvec for iterator */ if (advance) { @@ -252,6 +312,7 @@ static unsigned int __blk_recalc_rq_segments(struct request_queue *q, struct bio_vec bv, bvprv = { NULL }; int cluster, prev = 0; unsigned int seg_size, nr_phys_segs; + unsigned front_seg_size = bio->bi_seg_front_size; struct bio *fbio, *bbio; struct bvec_iter iter; @@ -272,7 +333,7 @@ static unsigned int __blk_recalc_rq_segments(struct request_queue *q, seg_size = 0; nr_phys_segs = 0; for_each_bio(bio) { - bio_for_each_page(bv, bio, iter) { + bio_for_each_segment(bv, bio, iter) { /* * If SG merging is disabled, each bio vector is * a segment @@ -294,20 +355,20 @@ static unsigned int __blk_recalc_rq_segments(struct request_queue *q, continue; } new_segment: - if (nr_phys_segs == 1 && seg_size > - fbio->bi_seg_front_size) - fbio->bi_seg_front_size = seg_size; + if (nr_phys_segs == 1 && seg_size > front_seg_size) + front_seg_size = seg_size; - nr_phys_segs++; bvprv = bv; prev = 1; - seg_size = bv.bv_len; + bvec_split_segs(q, &bv, &nr_phys_segs, &seg_size, + &front_seg_size, NULL); } bbio = bio; } - if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size) - fbio->bi_seg_front_size = seg_size; + if (nr_phys_segs == 1 && seg_size > front_seg_size) + front_seg_size = seg_size; + fbio->bi_seg_front_size = front_seg_size; if (seg_size > bbio->bi_seg_back_size) bbio->bi_seg_back_size = seg_size;