Commit f061656c authored by Eric Blake's avatar Eric Blake
Browse files

nbd: Implement client use of NBD FAST_ZERO 



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: default avatarEric Blake <eblake@redhat.com>
Message-Id: <20190823143726.27062-4-eblake@redhat.com>
Reviewed-by: default avatarVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
parent 0a479545

block/nbd.c

+7 −0
Original line number Diff line number Diff line
@@ -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;