[Qemu-devel] [PATCH 2/6 for-3.1] nbd: stop waiting for a NBD response with NBD_CMD_DISC

["Daniel P. Berrangé" <berrange@redhat.com>]

When sending a NBD_CMD_DISC message there is no reply expected,
however, the nbd_read_eof() coroutine is still waiting for a reply.
In a plain NBD connection this doesn't matter as it will just get an
EOF, however, on a TLS connection it will get an interrupted TLS data
packet. The nbd_read_eof() will then print an error message on the
console due to missing reply to NBD_CMD_DISC.

This can be seen with qemu-img

  $ qemu-img info \
      --object tls-creds-x509,dir=tlsdir,id=tls0,endpoint=client \
      --image-opts driver=nbd,host=127.0.0.1,port=9000,tls-creds=tls0
  qemu-img: Cannot read from TLS channel: Input/output error
  image: nbd://127.0.0.1:9000
  file format: nbd
  virtual size: 10M (10485760 bytes)
  disk size: unavailable

Simply setting the 'quit' flag after sending NBD_CMD_DISC is enough to
get the coroutine to stop waiting for a reply and thus supress the error
message. This fixes a regression introduced in

  commit be41c100c0d67f6072ddd4910c4b6f7d239f025f
  Author: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
  Date:   Fri May 26 14:09:13 2017 +0300

    nbd/client.c: use errp instead of LOG

    Move to modern errp scheme from just LOGging errors.

    Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
    Message-Id: <20170526110913.89098-1-vsementsov@virtuozzo.com>
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 block/nbd-client.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/block/nbd-client.c b/block/nbd-client.c
index 76e9ca3abe..5f63e4b8f1 100644
--- a/block/nbd-client.c
+++ b/block/nbd-client.c
@@ -961,6 +961,7 @@ void nbd_client_close(BlockDriverState *bs)
     }
 
     nbd_send_request(client->ioc, &request);
+    client->quit = true;
 
     nbd_teardown_connection(bs);
 }
-- 
2.19.1