linux-kernel - Re: [PATCH 02/17] block: introduce bio_remove_last

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Message-ID: <b443b3a1-ecc9-8238-1b3d-90870a25c793@suse.de>
Date:   Thu, 16 Feb 2017 13:08:22 +0100
From:   Johannes Thumshirn <jthumshirn@...e.de>
To:     Ming Lei <tom.leiming@...il.com>, Shaohua Li <shli@...nel.org>,
        Jens Axboe <axboe@...com>, linux-kernel@...r.kernel.org,
        linux-raid@...r.kernel.org, linux-block@...r.kernel.org,
        Christoph Hellwig <hch@...radead.org>,
        NeilBrown <neilb@...e.com>
Subject: Re: [PATCH 02/17] block: introduce bio_remove_last_page()

On 02/16/2017 12:45 PM, Ming Lei wrote:
> MD need this helper to remove the last added page, so introduce
> it.
> 
> Signed-off-by: Ming Lei <tom.leiming@...il.com>
> ---
>  block/bio.c         | 23 +++++++++++++++++++++++
>  include/linux/bio.h |  1 +
>  2 files changed, 24 insertions(+)
> 
> diff --git a/block/bio.c b/block/bio.c
> index 5eec5e08417f..0ce7ffcd7939 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -837,6 +837,29 @@ int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page
>  EXPORT_SYMBOL(bio_add_pc_page);
>  
>  /**
> + *	bio_remove_last_page	-	remove the last added page
> + *	@bio: destination bio
> + *
> + *	Attempt to remove the last added page from the bio_vec maplist.
> + */
> +void bio_remove_last_page(struct bio *bio)
> +{
> +	/*
> +	 * cloned bio must not modify vec list
> +	 */
> +	if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
> +		return;
> +
> +	if (bio->bi_vcnt > 0) {

In patch 1 you introduce bio_segments_all() with the log message 'So
that we can replace the direct access to .bi_vcnt.' Here you introduce a
new direct access to it (plus the duplicated WARN_ON_ONCE()).

Maybe use the helper directly here (I admit I haven't gone through the
whole series yet, so I can't see if the change is made later).

Byte,
	Johannes

-- 
Johannes Thumshirn                                          Storage
jthumshirn@...e.de                                +49 911 74053 689
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