Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755386AbcKOBB5 (ORCPT ); Mon, 14 Nov 2016 20:01:57 -0500 Received: from mail-vk0-f65.google.com ([209.85.213.65]:33489 "EHLO mail-vk0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755161AbcKOBBz (ORCPT ); Mon, 14 Nov 2016 20:01:55 -0500 MIME-Version: 1.0 In-Reply-To: <1478865957-25252-8-git-send-email-tom.leiming@gmail.com> References: <1478865957-25252-1-git-send-email-tom.leiming@gmail.com> <1478865957-25252-8-git-send-email-tom.leiming@gmail.com> From: Ming Lei Date: Tue, 15 Nov 2016 09:01:53 +0800 Message-ID: Subject: Re: [PATCH 07/12] dm: use bvec iterator helpers to implement .get_page and .next_page To: Jens Axboe , Linux Kernel Mailing List Cc: linux-block , Linux FS Devel , Christoph Hellwig , Ming Lei , Alasdair Kergon , Mike Snitzer , "maintainer:DEVICE-MAPPER (LVM)" , Shaohua Li , "open list:SOFTWARE RAID (Multiple Disks) SUPPORT" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2859 Lines: 82 On Fri, Nov 11, 2016 at 8:05 PM, Ming Lei wrote: > Firstly we have mature bvec/bio iterator helper for iterate each > page in one bio, not necessary to reinvent a wheel to do that. > > Secondly the coming multipage bvecs requires this patch. > > Also add comments about the direct access to bvec table. > > Signed-off-by: Ming Lei > --- > drivers/md/dm-io.c | 34 ++++++++++++++++++++++++---------- > 1 file changed, 24 insertions(+), 10 deletions(-) > > diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c > index 0bf1a12e35fe..2ef573c220fc 100644 > --- a/drivers/md/dm-io.c > +++ b/drivers/md/dm-io.c > @@ -162,7 +162,10 @@ struct dpages { > struct page **p, unsigned long *len, unsigned *offset); > void (*next_page)(struct dpages *dp); > > - unsigned context_u; > + union { > + unsigned context_u; > + struct bvec_iter context_bi; > + }; > void *context_ptr; > > void *vma_invalidate_address; > @@ -204,25 +207,36 @@ static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offse > static void bio_get_page(struct dpages *dp, struct page **p, > unsigned long *len, unsigned *offset) > { > - struct bio_vec *bvec = dp->context_ptr; > - *p = bvec->bv_page; > - *len = bvec->bv_len - dp->context_u; > - *offset = bvec->bv_offset + dp->context_u; > + struct bio_vec bv = bvec_iter_bvec((struct bio_vec *)dp->context_ptr, > + dp->context_bi); > + > + *p = bv.bv_page; > + *len = bv.bv_len; > + *offset = bv.bv_offset; > + > + /* avoid to figure out it in bio_next_page() again */ > + dp->context_bi.bi_sector = (sector_t)bv.bv_len; > } > > static void bio_next_page(struct dpages *dp) > { > - struct bio_vec *bvec = dp->context_ptr; > - dp->context_ptr = bvec + 1; > - dp->context_u = 0; > + unsigned int len = (unsigned int)dp->context_bi.bi_sector; > + > + bvec_iter_advance((struct bio_vec *)dp->context_ptr, > + &dp->context_bi, len); > } > > static void bio_dp_init(struct dpages *dp, struct bio *bio) > { > dp->get_page = bio_get_page; > dp->next_page = bio_next_page; > - dp->context_ptr = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter); > - dp->context_u = bio->bi_iter.bi_bvec_done; > + > + /* > + * We just use bvec iterator to retrieve pages, so it is ok to > + * access the bvec table directly here > + */ > + dp->context_ptr = bio->bi_io_vec; > + dp->context_bi = bio->bi_iter; > } Hi Alasdair, Mike, Christoph and anyone, Could you give this one a review? >From my test, it just works fine, and I believe it is a good cleanup. Thanks, Ming Lei