From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by kanga.kvack.org (Postfix) with ESMTP id 239486B0007 for ; Wed, 27 Jun 2018 11:55:59 -0400 (EDT) Received: by mail-ed1-f72.google.com with SMTP id o2-v6so1409978edt.4 for ; Wed, 27 Jun 2018 08:55:59 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id i3-v6si2213399edq.22.2018.06.27.08.55.57 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 27 Jun 2018 08:55:57 -0700 (PDT) Subject: Re: [PATCH V7 20/24] bcache: avoid to use bio_for_each_segment_all() in bch_bio_alloc_pages() References: <20180627124548.3456-1-ming.lei@redhat.com> <20180627124548.3456-21-ming.lei@redhat.com> From: Coly Li Message-ID: Date: Wed, 27 Jun 2018 23:55:33 +0800 MIME-Version: 1.0 In-Reply-To: <20180627124548.3456-21-ming.lei@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Ming Lei Cc: Jens Axboe , Christoph Hellwig , Kent Overstreet , David Sterba , Huang Ying , Mike Snitzer , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Theodore Ts'o , "Darrick J . Wong" , Filipe Manana , Randy Dunlap , linux-bcache@vger.kernel.org On 2018/6/27 8:45 PM, Ming Lei wrote: > bch_bio_alloc_pages() is always called on one new bio, so it is safe > to access the bvec table directly. Given it is the only kind of this > case, open code the bvec table access since bio_for_each_segment_all() > will be changed to support for iterating over multipage bvec. > > Cc: Coly Li > Cc: linux-bcache@vger.kernel.org > Signed-off-by: Ming Lei > --- > drivers/md/bcache/util.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/md/bcache/util.c b/drivers/md/bcache/util.c > index fc479b026d6d..9f2a6fd5dfc9 100644 > --- a/drivers/md/bcache/util.c > +++ b/drivers/md/bcache/util.c > @@ -268,7 +268,7 @@ int bch_bio_alloc_pages(struct bio *bio, gfp_t gfp_mask) > int i; > struct bio_vec *bv; > Hi Ming, > - bio_for_each_segment_all(bv, bio, i) { > + for (i = 0, bv = bio->bi_io_vec; i < bio->bi_vcnt; bv++) { Is it possible to treat this as a special condition of bio_for_each_segement_all() ? I mean only iterate one time in bvec_for_each_segment(). I hope the above change is not our last choice before I reply an Acked-by :-) Thanks. Coly Li > bv->bv_page = alloc_page(gfp_mask); > if (!bv->bv_page) { > while (--bv >= bio->bi_io_vec) >