From patchwork Tue Jan 9 02:34:40 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 10150891 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 1D417601A1 for ; Tue, 9 Jan 2018 02:35:15 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0B7AB289E3 for ; Tue, 9 Jan 2018 02:35:15 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id F241F289FF; Tue, 9 Jan 2018 02:35:14 +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 7D19F289E3 for ; Tue, 9 Jan 2018 02:35:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754166AbeAICfA (ORCPT ); Mon, 8 Jan 2018 21:35:00 -0500 Received: from mx1.redhat.com ([209.132.183.28]:52094 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751770AbeAICe6 (ORCPT ); Mon, 8 Jan 2018 21:34:58 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 37CFD15DF; Tue, 9 Jan 2018 02:34:58 +0000 (UTC) Received: from ming.t460p (ovpn-12-28.pek2.redhat.com [10.72.12.28]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0F9A260C7B; Tue, 9 Jan 2018 02:34:43 +0000 (UTC) Date: Tue, 9 Jan 2018 10:34:40 +0800 From: Ming Lei To: Dmitry Osipenko Cc: Jens Axboe , Christoph Hellwig , Alexander Viro , Kent Overstreet , 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 , Ulf Hansson , linux-mmc@vger.kernel.org Subject: Re: [PATCH V4 13/45] block: blk-merge: try to make front segments in full size Message-ID: <20180109023432.GB31067@ming.t460p> References: <20171218122247.3488-1-ming.lei@redhat.com> <20171218122247.3488-14-ming.lei@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.1 (2017-09-22) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Tue, 09 Jan 2018 02:34:58 +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 On Tue, Jan 09, 2018 at 12:09:27AM +0300, Dmitry Osipenko wrote: > On 18.12.2017 15:22, Ming Lei wrote: > > When merging one bvec into segment, if the bvec is too big > > to merge, current policy is to move the whole bvec into another > > new segment. > > > > This patchset changes the policy into trying to maximize size of > > front segments, that means in above situation, part of bvec > > is merged into current segment, and the remainder is put > > into next segment. > > > > This patch prepares for support multipage bvec because > > it can be quite common to see this case and we should try > > to make front segments in full size. > > > > Signed-off-by: Ming Lei > > --- > > block/blk-merge.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++----- > > 1 file changed, 49 insertions(+), 5 deletions(-) > > > > diff --git a/block/blk-merge.c b/block/blk-merge.c > > index a476337a8ff4..42ceb89bc566 100644 > > --- a/block/blk-merge.c > > +++ b/block/blk-merge.c > > @@ -109,6 +109,7 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, > > bool do_split = true; > > struct bio *new = NULL; > > const unsigned max_sectors = get_max_io_size(q, bio); > > + unsigned advance = 0; > > > > bio_for_each_segment(bv, bio, iter) { > > /* > > @@ -134,12 +135,32 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, > > } > > > > if (bvprvp && blk_queue_cluster(q)) { > > - if (seg_size + bv.bv_len > queue_max_segment_size(q)) > > - goto new_segment; > > if (!BIOVEC_PHYS_MERGEABLE(bvprvp, &bv)) > > goto new_segment; > > if (!BIOVEC_SEG_BOUNDARY(q, bvprvp, &bv)) > > 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. > > + */ > > + advance = queue_max_segment_size(q) - seg_size; > > + > > + if (advance > 0) { > > + seg_size += advance; > > + sectors += advance >> 9; > > + bv.bv_len -= advance; > > + bv.bv_offset += advance; > > + } > > + > > + /* > > + * Still need to put remainder of current > > + * bvec into a new segment. > > + */ > > + goto new_segment; > > + } > > > > seg_size += bv.bv_len; > > bvprv = bv; > > @@ -161,6 +182,12 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, > > seg_size = bv.bv_len; > > sectors += bv.bv_len >> 9; > > > > + /* restore the bvec for iterator */ > > + if (advance) { > > + bv.bv_len += advance; > > + bv.bv_offset -= advance; > > + advance = 0; > > + } > > } > > > > do_split = false; > > @@ -361,16 +388,29 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, > > { > > > > int nbytes = bvec->bv_len; > > + unsigned advance = 0; > > > > if (*sg && *cluster) { > > - if ((*sg)->length + nbytes > queue_max_segment_size(q)) > > - goto new_segment; > > - > > if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) > > goto new_segment; > > if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec)) > > goto new_segment; > > > > + /* > > + * try best to merge part of the bvec into previous > > + * segment and follow same policy with > > + * blk_bio_segment_split() > > + */ > > + if ((*sg)->length + nbytes > queue_max_segment_size(q)) { > > + advance = queue_max_segment_size(q) - (*sg)->length; > > + if (advance) { > > + (*sg)->length += advance; > > + bvec->bv_offset += advance; > > + bvec->bv_len -= advance; > > + } > > + goto new_segment; > > + } > > + > > (*sg)->length += nbytes; > > } else { > > new_segment: > > @@ -393,6 +433,10 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, > > > > sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); > > (*nsegs)++; > > + > > + /* for making iterator happy */ > > + bvec->bv_offset -= advance; > > + bvec->bv_len += advance; > > } > > *bvprv = *bvec; > > } > > > > Hello, > > This patch breaks MMC on next-20180108, in particular MMC doesn't work anymore > with this patch on NVIDIA Tegra20: > > <3>[ 36.622253] print_req_error: I/O error, dev mmcblk1, sector 512 > <3>[ 36.671233] print_req_error: I/O error, dev mmcblk2, sector 128 > <3>[ 36.711308] print_req_error: I/O error, dev mmcblk1, sector 31325304 > <3>[ 36.749232] print_req_error: I/O error, dev mmcblk2, sector 512 > <3>[ 36.761235] print_req_error: I/O error, dev mmcblk1, sector 31325816 > <3>[ 36.832039] print_req_error: I/O error, dev mmcblk2, sector 31259768 > <3>[ 99.793248] print_req_error: I/O error, dev mmcblk1, sector 31323136 > <3>[ 99.982043] print_req_error: I/O error, dev mmcblk1, sector 929792 > <3>[ 99.986301] print_req_error: I/O error, dev mmcblk1, sector 930816 > <3>[ 100.293624] print_req_error: I/O error, dev mmcblk1, sector 932864 > <3>[ 100.466839] print_req_error: I/O error, dev mmcblk1, sector 947200 > <3>[ 100.642955] print_req_error: I/O error, dev mmcblk1, sector 949248 > <3>[ 100.818838] print_req_error: I/O error, dev mmcblk1, sector 230400 > > Any attempt of mounting MMC block dev ends with a kernel crash. Reverting this > patch fixes the issue. Hi Dmitry, Thanks for your report! Could you share us what the segment limits are on your MMC? cat /sys/block/mmcN/queue/max_segment_size cat /sys/block/mmcN/queue/max_segments Please test the following patch to see if your issue can be fixed? --- Thanks, Ming diff --git a/block/blk-merge.c b/block/blk-merge.c index 446f63e076aa..cfab36c26608 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -431,12 +431,14 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); (*nsegs)++; + } + *bvprv = *bvec; + if (advance) { /* for making iterator happy */ bvec->bv_offset -= advance; bvec->bv_len += advance; } - *bvprv = *bvec; } static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv,