Re: [PATCH v9 01/41] block: add bio_add_zone_append_page

[Jens Axboe <axboe@kernel.dk>]

On 10/30/20 7:51 AM, Naohiro Aota wrote:
> From: Johannes Thumshirn <johannes.thumshirn@wdc.com>
> 
> Add bio_add_zone_append_page(), a wrapper around bio_add_hw_page() which
> is intended to be used by file systems that directly add pages to a bio
> instead of using bio_iov_iter_get_pages().

Not sure what this is for, since I'm only on one patch in the series...

> +/**
> + * bio_add_zone_append_page - attempt to add page to zone-append bio
> + * @bio: destination bio
> + * @page: page to add
> + * @len: vec entry length
> + * @offset: vec entry offset
> + *
> + * Attempt to add a page to the bio_vec maplist of a bio that will be submitted
> + * for a zone-append request. This can fail for a number of reasons, such as the
> + * bio being full or the target block device is not a zoned block device or
> + * other limitations of the target block device. The target block device must
> + * allow bio's up to PAGE_SIZE, so it is always possible to add a single page
> + * to an empty bio.
> + */

This should include a

Return value:

section, explaining how it returns number of bytes added (and why 0 is thus
a failure case).

> +int bio_add_zone_append_page(struct bio *bio, struct page *page,
> +			     unsigned int len, unsigned int offset)

Should this return unsigned int? If not, how would it work if someone
asked for INT_MAX + 4k.

-- 
Jens Axboe