nbd: Use low-level QIOChannel API in nbd_read_eof()

Instead of using the convenience wrapper qio_channel_read_all_eof(), use
the lower level QIOChannel API. This means duplicating some code, but
we'll need this because this coroutine yield is special: We want it to
be interruptible so that nbd_client_attach_aio_context() can correctly
reenter the coroutine.

This moves the bdrv_dec/inc_in_flight() pair into nbd_read_eof(), so
that connection_co will always sit in this exact qio_channel_yield()
call when bdrv_drain() returns.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

1 files changed, 1 insertions, 7 deletions

diff --git a/block/nbd-client.c b/block/nbd-client.c
index 5ce4aa9520..60f38f0320 100644
--- a/block/nbd-client.c
+++ b/block/nbd-client.c
@@ -84,15 +84,9 @@ static coroutine_fn void nbd_connection_entry(void *opaque)
          *
          * Therefore we keep an additional in_flight reference all the time and
          * only drop it temporarily here.
-         *
-         * FIXME This is not safe because the QIOChannel could wake up the
-         * coroutine for a second time; it is not prepared for coroutine
-         * resumption from external code.
          */
-        bdrv_dec_in_flight(s->bs);
         assert(s->reply.handle == 0);
-        ret = nbd_receive_reply(s->ioc, &s->reply, &local_err);
-        bdrv_inc_in_flight(s->bs);
+        ret = nbd_receive_reply(s->bs, s->ioc, &s->reply, &local_err);
 
         if (local_err) {
             trace_nbd_read_reply_entry_fail(ret, error_get_pretty(local_err));