From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [PATCH 03/33] block: convert to using sg helpers Date: Mon, 16 Jul 2007 21:14:18 +0200 Message-ID: <20070716191417.GK5195@kernel.dk> References: <11845792671245-git-send-email-jens.axboe@oracle.com> <11845792672399-git-send-email-jens.axboe@oracle.com> <200707162121.32936.bzolnier@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from brick.kernel.dk ([80.160.20.94]:14327 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761292AbXGPTO6 (ORCPT ); Mon, 16 Jul 2007 15:14:58 -0400 Content-Disposition: inline In-Reply-To: <200707162121.32936.bzolnier@gmail.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Bartlomiej Zolnierkiewicz Cc: linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org On Mon, Jul 16 2007, Bartlomiej Zolnierkiewicz wrote: > > Hi, > > On Monday 16 July 2007, Jens Axboe wrote: > > Convert the main rq mapper (blk_rq_map_sg()) to the sg helper setup. > > > > Signed-off-by: Jens Axboe > > --- > > block/ll_rw_blk.c | 19 ++++++++++++------- > > 1 files changed, 12 insertions(+), 7 deletions(-) > > > > diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c > > index ef42bb2..ab71087 100644 > > --- a/block/ll_rw_blk.c > > +++ b/block/ll_rw_blk.c > > @@ -30,6 +30,7 @@ > > #include > > #include > > #include > > +#include > > > > /* > > * for max sense size > > @@ -1307,9 +1308,11 @@ static int blk_hw_contig_segment(request_queue_t *q, struct bio *bio, > > * map a request to scatterlist, return number of sg entries setup. Caller > > * must make sure sg can hold rq->nr_phys_segments entries > > */ > > -int blk_rq_map_sg(request_queue_t *q, struct request *rq, struct scatterlist *sg) > > +int blk_rq_map_sg(request_queue_t *q, struct request *rq, > > + struct scatterlist *sglist) > > { > > struct bio_vec *bvec, *bvprv; > > + struct scatterlist *next_sg, *sg; > > struct bio *bio; > > int nsegs, i, cluster; > > > > @@ -1320,6 +1323,7 @@ int blk_rq_map_sg(request_queue_t *q, struct request *rq, struct scatterlist *sg > > * for each bio in rq > > */ > > bvprv = NULL; > > + sg = next_sg = &sglist[0]; > > rq_for_each_bio(bio, rq) { > > /* > > * for each segment in bio > > @@ -1328,7 +1332,7 @@ int blk_rq_map_sg(request_queue_t *q, struct request *rq, struct scatterlist *sg > > int nbytes = bvec->bv_len; > > > > if (bvprv && cluster) { > > - if (sg[nsegs - 1].length + nbytes > q->max_segment_size) > > + if (sg->length + nbytes > q->max_segment_size) > > goto new_segment; > > > > if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) > > @@ -1336,14 +1340,15 @@ int blk_rq_map_sg(request_queue_t *q, struct request *rq, struct scatterlist *sg > > if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec)) > > goto new_segment; > > > > - sg[nsegs - 1].length += nbytes; > > + sg->length += nbytes; > > } else { > > new_segment: > > - memset(&sg[nsegs],0,sizeof(struct scatterlist)); > > Is this intended? If so why this is no longer needed? It is, actually it's even required. All fields input fields should be set, the mapping/iommu helpers should set all output fields. But I understand your concerns, it's definitely something that should be kept an eye on. And I have so far. I even listed it as the primary concern in an email (off list) to Tomo today. -- Jens Axboe