Return-Path: Received: from mail-pg1-f195.google.com ([209.85.215.195]:43972 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389033AbeKPKug (ORCPT ); Fri, 16 Nov 2018 05:50:36 -0500 Received: by mail-pg1-f195.google.com with SMTP id n10-v6so9769938pgv.10 for ; Thu, 15 Nov 2018 16:40:24 -0800 (PST) Date: Thu, 15 Nov 2018 16:40:22 -0800 From: Omar Sandoval To: Ming Lei Cc: Jens Axboe , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Dave Chinner , Kent Overstreet , Mike Snitzer , dm-devel@redhat.com, Alexander Viro , linux-fsdevel@vger.kernel.org, Shaohua Li , linux-raid@vger.kernel.org, linux-erofs@lists.ozlabs.org, David Sterba , linux-btrfs@vger.kernel.org, "Darrick J . Wong" , linux-xfs@vger.kernel.org, Gao Xiang , Christoph Hellwig , Theodore Ts'o , linux-ext4@vger.kernel.org, Coly Li , linux-bcache@vger.kernel.org, Boaz Harrosh , Bob Peterson , cluster-devel@redhat.com Subject: Re: [PATCH V10 10/19] block: loop: pass multi-page bvec to iov_iter Message-ID: <20181116004022.GE23828@vader> References: <20181115085306.9910-1-ming.lei@redhat.com> <20181115085306.9910-11-ming.lei@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181115085306.9910-11-ming.lei@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Thu, Nov 15, 2018 at 04:52:57PM +0800, Ming Lei wrote: > iov_iter is implemented with bvec itererator, so it is safe to pass > multipage bvec to it, and this way is much more efficient than > passing one page in each bvec. > > Cc: Dave Chinner > Cc: Kent Overstreet > Cc: Mike Snitzer > Cc: dm-devel@redhat.com > Cc: Alexander Viro > Cc: linux-fsdevel@vger.kernel.org > Cc: Shaohua Li > Cc: linux-raid@vger.kernel.org > Cc: linux-erofs@lists.ozlabs.org > Cc: David Sterba > Cc: linux-btrfs@vger.kernel.org > Cc: Darrick J. Wong > Cc: linux-xfs@vger.kernel.org > Cc: Gao Xiang > Cc: Christoph Hellwig > Cc: Theodore Ts'o > Cc: linux-ext4@vger.kernel.org > Cc: Coly Li > Cc: linux-bcache@vger.kernel.org > Cc: Boaz Harrosh > Cc: Bob Peterson > Cc: cluster-devel@redhat.com Reviewed-by: Omar Sandoval Comments below. > Signed-off-by: Ming Lei > --- > drivers/block/loop.c | 23 ++++++++++++----------- > 1 file changed, 12 insertions(+), 11 deletions(-) > > diff --git a/drivers/block/loop.c b/drivers/block/loop.c > index bf6bc35aaf88..a3fd418ec637 100644 > --- a/drivers/block/loop.c > +++ b/drivers/block/loop.c > @@ -515,16 +515,16 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, > struct bio *bio = rq->bio; > struct file *file = lo->lo_backing_file; > unsigned int offset; > - int segments = 0; > + int nr_bvec = 0; > int ret; > > if (rq->bio != rq->biotail) { > - struct req_iterator iter; > + struct bvec_iter iter; > struct bio_vec tmp; > > __rq_for_each_bio(bio, rq) > - segments += bio_segments(bio); > - bvec = kmalloc_array(segments, sizeof(struct bio_vec), > + nr_bvec += bio_bvecs(bio); > + bvec = kmalloc_array(nr_bvec, sizeof(struct bio_vec), > GFP_NOIO); > if (!bvec) > return -EIO; > @@ -533,13 +533,14 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, > /* > * The bios of the request may be started from the middle of > * the 'bvec' because of bio splitting, so we can't directly > - * copy bio->bi_iov_vec to new bvec. The rq_for_each_segment > + * copy bio->bi_iov_vec to new bvec. The bio_for_each_bvec > * API will take care of all details for us. > */ > - rq_for_each_segment(tmp, rq, iter) { > - *bvec = tmp; > - bvec++; > - } > + __rq_for_each_bio(bio, rq) > + bio_for_each_bvec(tmp, bio, iter) { > + *bvec = tmp; > + bvec++; > + } Even if they're not strictly necessary, could you please include the curly braces for __rq_for_each_bio() here? > bvec = cmd->bvec; > offset = 0; > } else { > @@ -550,11 +551,11 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, > */ > offset = bio->bi_iter.bi_bvec_done; > bvec = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter); > - segments = bio_segments(bio); > + nr_bvec = bio_bvecs(bio); This scared me for a second, but it's fine to do here because we haven't actually enabled multipage bvecs yet, right? > } > atomic_set(&cmd->ref, 2); > > - iov_iter_bvec(&iter, rw, bvec, segments, blk_rq_bytes(rq)); > + iov_iter_bvec(&iter, rw, bvec, nr_bvec, blk_rq_bytes(rq)); > iter.iov_offset = offset; > > cmd->iocb.ki_pos = pos; > -- > 2.9.5 >