Detecting monitor by current coroutine works bad when we are not in
coroutine context. And that's exactly so in nbd reconnect code, where
qio_channel_socket_connect_sync() is called from thread.

Monitor is needed only to parse named file descriptor. So, let's just
parse it during nbd_open(), so that all further users of s->saddr don't
need to access monitor.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/nbd.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/block/nbd.c b/block/nbd.c
index f3a036354d..1c99654ef7 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -2140,6 +2140,12 @@ static SocketAddress *nbd_config(BDRVNBDState *s, QDict *options,
         goto done;
     }
 
+    if (socket_address_parse_named_fd(saddr, errp) < 0) {
+        qapi_free_SocketAddress(saddr);
+        saddr = NULL;
+        goto done;
+    }
+
 done:
     qobject_unref(addr);
     visit_free(iv);
-- 
2.29.2

On Thu, Jun 10, 2021 at 01:07:36PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> Detecting monitor by current coroutine works bad when we are not in
> coroutine context. And that's exactly so in nbd reconnect code, where
> qio_channel_socket_connect_sync() is called from thread.
> 
> Monitor is needed only to parse named file descriptor. So, let's just
> parse it during nbd_open(), so that all further users of s->saddr don't
> need to access monitor.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  block/nbd.c | 6 ++++++
>  1 file changed, 6 insertions(+)

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org