Re: [Qemu-devel] [PATCH v3] block: document semanatics of bdrv_co_preadv|pwritev

[Eric Blake]

On 08/04/2017 09:08 AM, Daniel P. Berrange wrote:
> Signed-off-by: Daniel P. Berrange <address@hidden>
> ---
> 
>  - Clarify that @bytes matches @qiov total size (Kevin)
> 
>  include/block/block_int.h | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)

[looks like the nongnu.org infrastructure is having heavy load today, so
mails are getting through more slowly than usual - leads to lots of
crossed emails, where I'm seeing replies or direct sends sooner than
list copies]

> +    /**
> +     * @offset: position in bytes to write at
> +     * @bytes: number of bytes to write
> +     * @qiov: the buffers containing data to write
> +     * @flags: zero or more of bits allowed by 'supported_write_flags'

maybe s/of //

> +     *
> +     * @offset and @bytes will be a multiple of 'request_alignment',
> +     * but the length of individual @qiov elements does not have to
> +     * be a multiple.
> +     *
> +     * @bytes will always equal the total size of @qiov, and will be
> +     * no larger than 'max_transfer'.
> +     *
> +     * The buffer in @qiov may point directly to guest memory.
> +     */
>      int coroutine_fn (*bdrv_co_pwritev)(BlockDriverState *bs,
>          uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags);

Do we make guarantees that the driver callback is never reached if the
image is currently read-only?  If so, is that a guarantee worth documenting?

Reviewed-by: Eric Blake <address@hidden>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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