23.08.2019 17:37, Eric Blake wrote:
> The client side is fairly straightforward: if the server advertised
> fast zero support, then we can map that to BDRV_REQ_NO_FALLBACK
> support. A server that advertises FAST_ZERO but not WRITE_ZEROES
> is technically broken, but we can ignore that situation as it does
> not change our behavior.
>
> Signed-off-by: Eric Blake <ebl...@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
>
> ---
>
> Perhaps this is worth merging with the previous patch.
> ---
> block/nbd.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/block/nbd.c b/block/nbd.c
> index beed46fb3414..8339d7106366 100644
> --- a/block/nbd.c
> +++ b/block/nbd.c
> @@ -1044,6 +1044,10 @@ static int
> nbd_client_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset,
> if (!(flags & BDRV_REQ_MAY_UNMAP)) {
> request.flags |= NBD_CMD_FLAG_NO_HOLE;
> }
> + if (flags & BDRV_REQ_NO_FALLBACK) {
> + assert(s->info.flags & NBD_FLAG_SEND_FAST_ZERO);
> + request.flags |= NBD_CMD_FLAG_FAST_ZERO;
> + }
>
> if (!bytes) {
> return 0;
> @@ -1239,6 +1243,9 @@ static int nbd_client_connect(BlockDriverState *bs,
> Error **errp)
> }
> if (s->info.flags & NBD_FLAG_SEND_WRITE_ZEROES) {
> bs->supported_zero_flags |= BDRV_REQ_MAY_UNMAP;
> + if (s->info.flags & NBD_FLAG_SEND_FAST_ZERO) {
> + bs->supported_zero_flags |= BDRV_REQ_NO_FALLBACK;
> + }
> }
>
> s->sioc = sioc;
>
--
Best regards,
Vladimir
