Re: [PATCH 02/17] block: introduce bio_remove_last_page()

Johannes Thumshirn
2017-02-16T12:08:26Z

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@gmail.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

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Johannes Thumshirn Storage
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