linux-kernel - Re: [RESEND PATCH V5 12/33] block: introduce bio

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Date:   Fri, 25 May 2018 00:42:27 -0400
From:   Kent Overstreet <kent.overstreet@...il.com>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     Jens Axboe <axboe@...com>, Christoph Hellwig <hch@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        David Sterba <dsterba@...e.cz>,
        Huang Ying <ying.huang@...el.com>,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        Theodore Ts'o <tytso@....edu>,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        Coly Li <colyli@...e.de>, Filipe Manana <fdmanana@...il.com>
Subject: Re: [RESEND PATCH V5 12/33] block: introduce bio_segments()

On Fri, May 25, 2018 at 11:46:00AM +0800, Ming Lei wrote:
> There are still cases in which we need to use bio_segments() for get the
> number of segment, so introduce it.
> 
> Signed-off-by: Ming Lei <ming.lei@...hat.com>
> ---
>  include/linux/bio.h | 25 ++++++++++++++++++++-----
>  1 file changed, 20 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index 08af9272687f..b24c00f99c9c 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -227,9 +227,9 @@ static inline bool bio_rewind_iter(struct bio *bio, struct bvec_iter *iter,
>  
>  #define bio_iter_last(bvec, iter) ((iter).bi_size == (bvec).bv_len)
>  
> -static inline unsigned bio_pages(struct bio *bio)
> +static inline unsigned __bio_elements(struct bio *bio, bool seg)

This is a rather silly helper function, there isn't any actual code that's
shared, everything's behind an if () statement. Just open code it in bio_pages()
and bio_segments()

>  {
> -	unsigned segs = 0;
> +	unsigned elems = 0;
>  	struct bio_vec bv;
>  	struct bvec_iter iter;
>  
> @@ -249,10 +249,25 @@ static inline unsigned bio_pages(struct bio *bio)
>  		break;
>  	}
>  
> -	bio_for_each_page(bv, bio, iter)
> -		segs++;
> +	if (!seg) {
> +		bio_for_each_page(bv, bio, iter)
> +			elems++;
> +	} else {
> +		bio_for_each_segment(bv, bio, iter)
> +			elems++;
> +	}
> +
> +	return elems;
> +}
> +
> +static inline unsigned bio_pages(struct bio *bio)
> +{
> +	return __bio_elements(bio, false);
> +}
>  
> -	return segs;
> +static inline unsigned bio_segments(struct bio *bio)
> +{
> +	return __bio_elements(bio, true);
>  }
>  
>  /*
> -- 
> 2.9.5
>