sheepdog: fix co_recv coroutine context

The co_recv coroutine has two things that will try to enter it:

  1. The select(2) read callback on the sheepdog socket.
  2. The aio_add_request() blocking operations, including a coroutine
     mutex.

This patch fixes it by setting NULL to co_recv before sending data.

In future, we should make the sheepdog driver fully coroutine-based
and simplify request handling.

Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/sheepdog.c

@@ -629,6 +629,9 @@ static void coroutine_fn aio_read_response(void *opaque)
 
     switch (acb->aiocb_type) {
     case AIOCB_WRITE_UDATA:
+        /* this coroutine context is no longer suitable for co_recv
+         * because we may send data to update vdi objects */
+        s->co_recv = NULL;
         if (!is_data_obj(aio_req->oid)) {
             break;
         }