Re: [Qemu-devel] [PATCH 1/6] block: Introduce bdrv_preadv()

[Eric Blake <eblake@redhat.com>]

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On 06/10/2016 10:05 AM, Kevin Wolf wrote:
> We already have a byte-based bdrv_pwritev(), but the read counterpart
> was still missing. This commit adds it.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/io.c            | 20 +++++++++++++-------
>  include/block/block.h |  1 +
>  2 files changed, 14 insertions(+), 7 deletions(-)
> 

Worth adding a flags argument while at it? But bdrv_pwritev() lacks one,
so for symmetry reasons, I'm okay if you don't bother.

> +int bdrv_preadv(BlockDriverState *bs, int64_t offset, QEMUIOVector *qiov)
> +{
> +    int ret;
> +
> +    ret = bdrv_prwv_co(bs, offset, qiov, false, 0);
> +    if (ret < 0) {
> +        return ret;
> +    }
> +
> +    return qiov->size;

This implies we never have a short read, it's an all-or-none error or
success.  Matches what we've done elsewhere, so I guess it's right.

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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