From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753608AbYJAIL0 (ORCPT ); Wed, 1 Oct 2008 04:11:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752052AbYJAILP (ORCPT ); Wed, 1 Oct 2008 04:11:15 -0400 Received: from pasmtpb.tele.dk ([80.160.77.98]:57484 "EHLO pasmtpB.tele.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750769AbYJAILO (ORCPT ); Wed, 1 Oct 2008 04:11:14 -0400 Date: Wed, 1 Oct 2008 10:10:56 +0200 From: Jens Axboe To: "Martin K. Petersen" Cc: neilb@suse.de, agk@sourceware.org, linux-kernel@vger.kernel.org, dm-devel@redhat.com Subject: Re: [PATCH 5/7] block: Find bio sector offset given idx and offset Message-ID: <20081001081056.GB19428@kernel.dk> References: <1222846723-18213-1-git-send-email-martin.petersen@oracle.com> <1222846723-18213-6-git-send-email-martin.petersen@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1222846723-18213-6-git-send-email-martin.petersen@oracle.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 01 2008, Martin K. Petersen wrote: > Helper function to find the sector offset in a bio given bvec index > and page offset. > > Signed-off-by: Martin K. Petersen > --- > fs/bio.c | 34 ++++++++++++++++++++++++++++++++++ > include/linux/bio.h | 1 + > 2 files changed, 35 insertions(+), 0 deletions(-) > > diff --git a/fs/bio.c b/fs/bio.c > index e56e768..55ee2fd 100644 > --- a/fs/bio.c > +++ b/fs/bio.c > @@ -1300,6 +1300,40 @@ struct bio_pair *bio_split(struct bio *bi, mempool_t *pool, int first_sectors) > return bp; > } > > +/** > + * bio_sector_offset - Find hardware sector offset in bio > + * @bio: bio to inspect > + * @index: bio_vec index > + * @offset: offset in bv_page > + * > + * Return the number of hardware sectors between beginning of bio > + * and an end point indicated by a bio_vec index and an offset > + * within that vector's page. > + */ > +sector_t bio_sector_offset(struct bio *bio, unsigned short index, > + unsigned int offset) > +{ > + struct bio_vec *bv; > + unsigned int sector_sz = bio->bi_bdev->bd_disk->queue->hardsect_size; > + sector_t sectors; > + int i; > + > + sectors = 0; > + > + BUG_ON(index >= bio->bi_vcnt); > + > + bio_for_each_segment(bv, bio, i) { > + if (i == index) { > + if (offset > bv->bv_offset) > + sectors += (offset - bv->bv_offset) / sector_sz; > + return sectors; > + } > + > + sectors += bv->bv_len / sector_sz; > + } > + > + BUG(); > +} Too may BUG's there, me thinks, and the interface looks fragile. What if the bio is alreday done (bi_idx == bi_vcnt)? I'd prefer something ala: sector_t bio_sector_offset(struct bio *bio, unsigned short index, unsigned int offset) { unsigned int sector_sz = queue_hardsect_size(bio->bi_bdev->bd_disk->queue); struct bio_vec *bv; sector_t sectors; int i; sectors = 0; /* total start of bio current start? */ #if 0 if (index >= bio->bi_vcnt) index = bio->bi_vcnt - 1; __bio_for_each_segment(bv, bio, i, 0) { #else if (index > bio->bi_idx) return 0; bio_for_each_segment(bv, bio, i) { #endif if (i == index) { if (offset > bv->bv_offset) sectors += (offset - bv->bv_offset) / sector_sz; break; } sectors += bv->bv_len / sector_sz; } return sectors; } Depending on which interface you want, pick one of the if/else parts :-) -- Jens Axboe