On 18/09/2017 15:59, Vladimir Sementsov-Ogievskiy wrote:
> Read the whole reply in one place - in nbd_read_reply_entry.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
> ---
> block/nbd-client.h | 1 +
> block/nbd-client.c | 42 ++++++++++++++++++++++++------------------
> 2 files changed, 25 insertions(+), 18 deletions(-)
>
> diff --git a/block/nbd-client.h b/block/nbd-client.h
> index b1900e6a6d..3f97d31013 100644
> --- a/block/nbd-client.h
> +++ b/block/nbd-client.h
> @@ -21,6 +21,7 @@ typedef struct {
> Coroutine *coroutine;
> bool receiving; /* waiting for read_reply_co? */
> NBDRequest *request;
> + QEMUIOVector *qiov;
> } NBDClientRequest;
>
> typedef struct NBDClientSession {
> diff --git a/block/nbd-client.c b/block/nbd-client.c
> index 5f241ecc22..f7b642f079 100644
> --- a/block/nbd-client.c
> +++ b/block/nbd-client.c
> @@ -98,6 +98,21 @@ static coroutine_fn void nbd_read_reply_entry(void *opaque)
> break;
> }
>
> + if (s->reply.error == 0 &&
> + s->requests[i].request->type == NBD_CMD_READ)
> + {
> + QEMUIOVector *qiov = s->requests[i].qiov;
> + assert(qiov != NULL);
> + assert(s->requests[i].request->len ==
> + iov_size(qiov->iov, qiov->niov));
> + if (qio_channel_readv_all(s->ioc, qiov->iov, qiov->niov,
> + NULL) < 0)
> + {
> + s->reply.error = EIO;
> + break;
> + }
> + }
I am not sure this is an improvement. In principle you could have
commands that read replies a bit at a time without using a QEMUIOVector.
Paolo
> /* We're woken up again by the request itself. Note that there
> * is no race between yielding and reentering read_reply_co. This
> * is because:
> @@ -118,6 +133,7 @@ static coroutine_fn void nbd_read_reply_entry(void
> *opaque)
> s->read_reply_co = NULL;
> }
>
> +/* qiov should be provided for READ and WRITE */
> static int nbd_co_send_request(BlockDriverState *bs,
> NBDRequest *request,
> QEMUIOVector *qiov)
> @@ -145,6 +161,7 @@ static int nbd_co_send_request(BlockDriverState *bs,
>
> request->handle = INDEX_TO_HANDLE(s, i);
> s->requests[i].request = request;
> + s->requests[i].qiov = qiov;
>
> if (s->quit) {
> rc = -EIO;
> @@ -155,7 +172,8 @@ static int nbd_co_send_request(BlockDriverState *bs,
> goto err;
> }
>
> - if (qiov) {
> + if (s->requests[i].request->type == NBD_CMD_WRITE) {
> + assert(qiov);
> qio_channel_set_cork(s->ioc, true);
> rc = nbd_send_request(s->ioc, request);
> if (rc >= 0 && !s->quit) {
> @@ -181,9 +199,7 @@ err:
> return rc;
> }
>
> -static int nbd_co_receive_reply(NBDClientSession *s,
> - NBDRequest *request,
> - QEMUIOVector *qiov)
> +static int nbd_co_receive_reply(NBDClientSession *s, NBDRequest *request)
> {
> int ret;
> int i = HANDLE_TO_INDEX(s, request->handle);
> @@ -197,14 +213,6 @@ static int nbd_co_receive_reply(NBDClientSession *s,
> } else {
> assert(s->reply.handle == request->handle);
> ret = -s->reply.error;
> - if (qiov && s->reply.error == 0) {
> - assert(request->len == iov_size(qiov->iov, qiov->niov));
> - if (qio_channel_readv_all(s->ioc, qiov->iov, qiov->niov,
> - NULL) < 0) {
> - ret = -EIO;
> - s->quit = true;
> - }
> - }
>
> /* Tell the read handler to read another header. */
> s->reply.handle = 0;
> @@ -232,16 +240,14 @@ static int nbd_co_request(BlockDriverState *bs,
> NBDClientSession *client = nbd_get_client_session(bs);
> int ret;
>
> - assert(!qiov || request->type == NBD_CMD_WRITE ||
> - request->type == NBD_CMD_READ);
> - ret = nbd_co_send_request(bs, request,
> - request->type == NBD_CMD_WRITE ? qiov : NULL);
> + assert((qiov == NULL) !=
> + (request->type == NBD_CMD_WRITE || request->type ==
> NBD_CMD_READ));
> + ret = nbd_co_send_request(bs, request, qiov);
> if (ret < 0) {
> return ret;
> }
>
> - return nbd_co_receive_reply(client, request,
> - request->type == NBD_CMD_READ ? qiov : NULL);
> + return nbd_co_receive_reply(client, request);
> }
>
> int nbd_client_co_preadv(BlockDriverState *bs, uint64_t offset,
>
