Re: [PATCH V11 17/19] block: document usage of bio iterator helpers

Nikolay Borisov
2018-11-21T07:45:33Z

On 21.11.18 г. 5:23 ч., Ming Lei wrote:
> Now multi-page bvec is supported, some helpers may return page by
> page, meantime some may return segment by segment, this patch
> documents the usage.
>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
> Documentation/block/biovecs.txt | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/Documentation/block/biovecs.txt b/Documentation/block/biovecs.txt
> index 25689584e6e0..bb008f7afb05 100644
> --- a/Documentation/block/biovecs.txt
> +++ b/Documentation/block/biovecs.txt
> @@ -117,3 +117,27 @@ Other implications:
> size limitations and the limitations of the underlying devices. Thus
> there's no need to define ->merge_bvec_fn() callbacks for individual block
> drivers.
> +
> +Usage of helpers:
> +=================
> +
> +* The following helpers whose names have the suffix of "_all" can only be used
> +on non-BIO_CLONED bio. They are usually used by filesystem code. Drivers
> +shouldn't use them because the bio may have been split before it reached the
> +driver.
> +
> + bio_for_each_segment_all()
> + bio_first_bvec_all()
> + bio_first_page_all()
> + bio_last_bvec_all()
> +
> +* The following helpers iterate over single-page bvecs. The passed 'struct
> +bio_vec' will contain a single-page IO vector during the iteration
> +
> + bio_for_each_segment()
> + bio_for_each_segment_all()
> +
> +* The following helpers iterate over single-page bvecs. The passed 'struct
> +bio_vec' will contain a single-page IO vector during the iteration
> +
> + bio_for_each_bvec()

Just put this helper right below the above 2, no need to repeat the
explanation. Also I'd suggest introducing another catch-all sentence
"All other helpers are assumed to iterate multipage bio vecs" and
perhaps give an example with 1-2 helpers.

>