From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753900AbcEYIwN (ORCPT ); Wed, 25 May 2016 04:52:13 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:46305 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751969AbcEYIwI (ORCPT ); Wed, 25 May 2016 04:52:08 -0400 MIME-Version: 1.0 In-Reply-To: References: Date: Wed, 25 May 2016 16:52:05 +0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC 1/3] block: Introduce blk_bio_map_sg() to map one bio From: Ming Lei To: Baolin Wang Cc: Jens Axboe , Alasdair Kergon , Mike Snitzer , "open list:DEVICE-MAPPER (LVM)" , Herbert Xu , David Miller , ebiggers3@gmail.com, js1304@gmail.com, tadeusz.struk@intel.com, smueller@chronox.de, standby24x7@gmail.com, Shaohua Li , Dan Williams , "Martin K. Petersen" , Sagi Grimberg , Kent Overstreet , Keith Busch , Tejun Heo , Mark Brown , Arnd Bergmann , linux-crypto@vger.kernel.org, linux-block@vger.kernel.org, "open list:SOFTWARE RAID (Multiple Disks) SUPPORT" , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 25, 2016 at 2:12 PM, Baolin Wang wrote: > In dm-crypt, it need to map one bio to scatterlist for improving the > hardware engine encryption efficiency. Thus this patch introduces the > blk_bio_map_sg() function to map one bio with scatterlists. > > Signed-off-by: Baolin Wang > --- > block/blk-merge.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ > include/linux/blkdev.h | 3 +++ > 2 files changed, 48 insertions(+) > > diff --git a/block/blk-merge.c b/block/blk-merge.c > index 2613531..9b92af4 100644 > --- a/block/blk-merge.c > +++ b/block/blk-merge.c > @@ -417,6 +417,51 @@ single_segment: > } > > /* > + * map a bio to scatterlist, return number of sg entries setup. > + */ > +int blk_bio_map_sg(struct request_queue *q, struct bio *bio, > + struct scatterlist *sglist, > + struct scatterlist **sg) > +{ > + struct bio_vec bvec, bvprv = { NULL }; > + struct bvec_iter iter; > + int nsegs, cluster; > + > + nsegs = 0; > + cluster = blk_queue_cluster(q); > + > + if (bio->bi_rw & REQ_DISCARD) { > + /* > + * This is a hack - drivers should be neither modifying the > + * biovec, nor relying on bi_vcnt - but because of > + * blk_add_request_payload(), a discard bio may or may not have > + * a payload we need to set up here (thank you Christoph) and > + * bi_vcnt is really the only way of telling if we need to. > + */ > + > + if (bio->bi_vcnt) > + goto single_segment; > + > + return 0; > + } > + > + if (bio->bi_rw & REQ_WRITE_SAME) { > +single_segment: > + *sg = sglist; > + bvec = bio_iovec(bio); > + sg_set_page(*sg, bvec.bv_page, bvec.bv_len, bvec.bv_offset); > + return 1; > + } > + > + bio_for_each_segment(bvec, bio, iter) > + __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg, > + &nsegs, &cluster); > + > + return nsegs; > +} > +EXPORT_SYMBOL(blk_bio_map_sg); You can use __blk_bios_map_sg() to implement blk_bio_map_sg(), then code duplication may be avoided. > + > +/* > * map a request to scatterlist, return number of sg entries setup. Caller > * must make sure sg can hold rq->nr_phys_segments entries > */ > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h > index 1fd8fdf..e5de4f8 100644 > --- a/include/linux/blkdev.h > +++ b/include/linux/blkdev.h > @@ -1013,6 +1013,9 @@ extern void blk_queue_write_cache(struct request_queue *q, bool enabled, bool fu > extern struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev); > > extern int blk_rq_map_sg(struct request_queue *, struct request *, struct scatterlist *); > +extern int blk_bio_map_sg(struct request_queue *q, struct bio *bio, > + struct scatterlist *sglist, > + struct scatterlist **sg); > extern void blk_dump_rq_flags(struct request *, char *); > extern long nr_blockdev_pages(void); > > -- > 1.7.9.5 >