Re: [PATCH 5/6] block/nbd: Do not force-cap *pnum

[Eric Blake <eblake@redhat.com>]

On Thu, Jun 17, 2021 at 05:52:46PM +0200, Max Reitz wrote:
> bdrv_co_block_status() does it for us, we do not need to do it here.
> 
> The advantage of not capping *pnum is that bdrv_co_block_status() can
> cache larger data regions than requested by its caller.
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  block/nbd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

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

> 
> diff --git a/block/nbd.c b/block/nbd.c
> index 616f9ae6c4..930bd234de 100644
> --- a/block/nbd.c
> +++ b/block/nbd.c
> @@ -1702,7 +1702,7 @@ static int coroutine_fn nbd_client_co_block_status(
>          .type = NBD_CMD_BLOCK_STATUS,
>          .from = offset,
>          .len = MIN(QEMU_ALIGN_DOWN(INT_MAX, bs->bl.request_alignment),
> -                   MIN(bytes, s->info.size - offset)),
> +                   s->info.size - offset),
>          .flags = NBD_CMD_FLAG_REQ_ONE,

I'd love to someday get rid of using NBD_CMD_FLAG_REQ_ONE (so the
server can reply with more extents in one go), but that's a bigger
task and unrelated to your block-layer cache.

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