From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kent Overstreet Subject: Re: [PATCH v2 21/26] block: Convert some code to bio_for_each_segment_all() Date: Thu, 20 Sep 2012 17:50:35 -0700 Message-ID: <20120921005035.GO5519@google.com> References: <1347322957-25260-1-git-send-email-koverstreet@google.com> <1347322957-25260-22-git-send-email-koverstreet@google.com> <20120921003832.GY7264@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20120921003832.GY7264-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> Sender: linux-bcache-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Tejun Heo Cc: linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org, neilb-l3A5Bk7waGM@public.gmane.org List-Id: linux-bcache@vger.kernel.org On Thu, Sep 20, 2012 at 05:38:32PM -0700, Tejun Heo wrote: > On Mon, Sep 10, 2012 at 05:22:32PM -0700, Kent Overstreet wrote: > > A few places in the code were either open coding or using the wrong > > version - fix. > > > > Signed-off-by: Kent Overstreet > > CC: Jens Axboe > > CC: NeilBrown > > --- > > --- a/drivers/md/raid1.c > > +++ b/drivers/md/raid1.c > > @@ -921,7 +921,7 @@ static void alloc_behind_pages(struct bio *bio, struct r1bio *r1_bio) > > if (unlikely(!bvecs)) > > return; > > > > - bio_for_each_segment(bvec, bio, i) { > > + bio_for_each_segment_all(bvec, bio, i) { > > I don't get this conversion. Why is this necessary? Not necessary, just a consistency thing - this bio is a clone that md owns (and the clone was trimmed, so we know bi_idx is 0). Also, it wasn't an issue here but after the patch that introduces the bvec iter it's no longer possible to modify the biovec through bio_for_each_segment_all() - it doesn't increment a pointer to the current bvec, you pass in a struct bio_vec (not a pointer) which is updated with what the current biovec would be (taking into account bi_bvec_done and bi_size). So because of that it is IMO more worthwhile to be consistent about bio_for_each_segment()/bio_for_each_segment_all() usage. Suppose I should stick all that in the patch description.