Return-Path: Received: from mail-pl1-f194.google.com ([209.85.214.194]:32804 "EHLO mail-pl1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727175AbeKPInp (ORCPT ); Fri, 16 Nov 2018 03:43:45 -0500 Received: by mail-pl1-f194.google.com with SMTP id w22-v6so10154855plk.0 for ; Thu, 15 Nov 2018 14:34:02 -0800 (PST) Date: Thu, 15 Nov 2018 14:33:58 -0800 From: Omar Sandoval To: Ming Lei Cc: Jens Axboe , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Dave Chinner , Kent Overstreet , Mike Snitzer , dm-devel@redhat.com, Alexander Viro , linux-fsdevel@vger.kernel.org, Shaohua Li , linux-raid@vger.kernel.org, linux-erofs@lists.ozlabs.org, David Sterba , linux-btrfs@vger.kernel.org, "Darrick J . Wong" , linux-xfs@vger.kernel.org, Gao Xiang , Christoph Hellwig , Theodore Ts'o , linux-ext4@vger.kernel.org, Coly Li , linux-bcache@vger.kernel.org, Boaz Harrosh , Bob Peterson , cluster-devel@redhat.com Subject: Re: [PATCH V10 04/19] block: use bio_for_each_bvec() to map sg Message-ID: <20181115223358.GE9348@vader> References: <20181115085306.9910-1-ming.lei@redhat.com> <20181115085306.9910-5-ming.lei@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181115085306.9910-5-ming.lei@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Thu, Nov 15, 2018 at 04:52:51PM +0800, Ming Lei wrote: > It is more efficient to use bio_for_each_bvec() to map sg, meantime > we have to consider splitting multipage bvec as done in blk_bio_segment_split(). > > Cc: Dave Chinner > Cc: Kent Overstreet > Cc: Mike Snitzer > Cc: dm-devel@redhat.com > Cc: Alexander Viro > Cc: linux-fsdevel@vger.kernel.org > Cc: Shaohua Li > Cc: linux-raid@vger.kernel.org > Cc: linux-erofs@lists.ozlabs.org > Cc: David Sterba > Cc: linux-btrfs@vger.kernel.org > Cc: Darrick J. Wong > Cc: linux-xfs@vger.kernel.org > Cc: Gao Xiang > Cc: Christoph Hellwig > Cc: Theodore Ts'o > Cc: linux-ext4@vger.kernel.org > Cc: Coly Li > Cc: linux-bcache@vger.kernel.org > Cc: Boaz Harrosh > Cc: Bob Peterson > Cc: cluster-devel@redhat.com Reviewed-by: Omar Sandoval > Signed-off-by: Ming Lei > --- > block/blk-merge.c | 72 +++++++++++++++++++++++++++++++++++++++---------------- > 1 file changed, 52 insertions(+), 20 deletions(-) > > diff --git a/block/blk-merge.c b/block/blk-merge.c > index 6f7deb94a23f..cb9f49bcfd36 100644 > --- a/block/blk-merge.c > +++ b/block/blk-merge.c > @@ -473,6 +473,56 @@ static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, > return biovec_phys_mergeable(q, &end_bv, &nxt_bv); > } > > +static struct scatterlist *blk_next_sg(struct scatterlist **sg, > + struct scatterlist *sglist) > +{ > + if (!*sg) > + return sglist; > + else { > + /* > + * If the driver previously mapped a shorter > + * list, we could see a termination bit > + * prematurely unless it fully inits the sg > + * table on each mapping. We KNOW that there > + * must be more entries here or the driver > + * would be buggy, so force clear the > + * termination bit to avoid doing a full > + * sg_init_table() in drivers for each command. > + */ > + sg_unmark_end(*sg); > + return sg_next(*sg); > + } > +} > + > +static unsigned blk_bvec_map_sg(struct request_queue *q, > + struct bio_vec *bvec, struct scatterlist *sglist, > + struct scatterlist **sg) > +{ > + unsigned nbytes = bvec->bv_len; > + unsigned nsegs = 0, total = 0; > + > + while (nbytes > 0) { > + unsigned seg_size; > + struct page *pg; > + unsigned offset, idx; > + > + *sg = blk_next_sg(sg, sglist); > + > + seg_size = min(nbytes, queue_max_segment_size(q)); > + offset = (total + bvec->bv_offset) % PAGE_SIZE; > + idx = (total + bvec->bv_offset) / PAGE_SIZE; > + pg = nth_page(bvec->bv_page, idx); > + > + sg_set_page(*sg, pg, seg_size, offset); > + > + total += seg_size; > + nbytes -= seg_size; > + nsegs++; > + } > + > + return nsegs; > +} > + > static inline void > __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, > struct scatterlist *sglist, struct bio_vec *bvprv, > @@ -490,25 +540,7 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, > (*sg)->length += nbytes; > } else { > new_segment: > - if (!*sg) > - *sg = sglist; > - else { > - /* > - * If the driver previously mapped a shorter > - * list, we could see a termination bit > - * prematurely unless it fully inits the sg > - * table on each mapping. We KNOW that there > - * must be more entries here or the driver > - * would be buggy, so force clear the > - * termination bit to avoid doing a full > - * sg_init_table() in drivers for each command. > - */ > - sg_unmark_end(*sg); > - *sg = sg_next(*sg); > - } > - > - sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); > - (*nsegs)++; > + (*nsegs) += blk_bvec_map_sg(q, bvec, sglist, sg); > } > *bvprv = *bvec; > } > @@ -530,7 +562,7 @@ static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, > int cluster = blk_queue_cluster(q), nsegs = 0; > > for_each_bio(bio) > - bio_for_each_segment(bvec, bio, iter) > + bio_for_each_bvec(bvec, bio, iter) > __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg, > &nsegs, &cluster); > > -- > 2.9.5 >