linux-kernel - Re: [PATCH V11 12/19] block: allow bio_for_each_segment

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Message-ID: <20181123021933.GB20110@ming.t460p>
Date:   Fri, 23 Nov 2018 10:19:34 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Theodore Ts'o <tytso@....edu>, Omar Sandoval <osandov@...com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Dave Chinner <dchinner@...hat.com>,
        Kent Overstreet <kent.overstreet@...il.com>,
        Mike Snitzer <snitzer@...hat.com>, dm-devel@...hat.com,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org, Shaohua Li <shli@...nel.org>,
        linux-raid@...r.kernel.org, David Sterba <dsterba@...e.com>,
        linux-btrfs@...r.kernel.org,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        linux-xfs@...r.kernel.org, Gao Xiang <gaoxiang25@...wei.com>,
        linux-ext4@...r.kernel.org, Coly Li <colyli@...e.de>,
        linux-bcache@...r.kernel.org, Boaz Harrosh <ooo@...ctrozaur.com>,
        Bob Peterson <rpeterso@...hat.com>, cluster-devel@...hat.com
Subject: Re: [PATCH V11 12/19] block: allow bio_for_each_segment_all() to
 iterate over multi-page bvec

On Thu, Nov 22, 2018 at 12:03:15PM +0100, Christoph Hellwig wrote:
> > +/* used for chunk_for_each_segment */
> > +static inline void bvec_next_segment(const struct bio_vec *bvec,
> > +				     struct bvec_iter_all *iter_all)
> 
> FYI, chunk_for_each_segment doesn't exist anymore, this is
> bvec_for_each_segment now.  Not sure the comment helps much, though.

OK, will remove the comment.

> 
> > +{
> > +	struct bio_vec *bv = &iter_all->bv;
> > +
> > +	if (bv->bv_page) {
> > +		bv->bv_page += 1;
> 
> I think this needs to use nth_page() given that with discontigmem
> page structures might not be allocated contigously.

Good catch!

Thanks,
Ming