[qemu-xen staging] block/nbd: on shutdown terminate connection attempt

[patchbot@xxxxxxx]

commit fbeb3e63b34a1af4a968031de1c82e5edf20bf6c
Author:     Vladimir Sementsov-Ogievskiy <vsementsov@xxxxxxxxxxxxx>
AuthorDate: Mon Jul 27 21:47:49 2020 +0300
Commit:     Eric Blake <eblake@xxxxxxxxxx>
CommitDate: Tue Jul 28 09:54:43 2020 -0500

    block/nbd: on shutdown terminate connection attempt
    
    On shutdown nbd driver may be in a connecting state. We should shutdown
    it as well, otherwise we may hang in
    nbd_teardown_connection, waiting for conneciton_co to finish in
    BDRV_POLL_WHILE(bs, s->connection_co) loop if remote server is down.
    
    How to reproduce the dead lock:
    
    1. Create nbd-fault-injector.conf with the following contents:
    
    [inject-error "mega1"]
    event=data
    io=readwrite
    when=before
    
    2. In one terminal run nbd-fault-injector in a loop, like this:
    
    n=1; while true; do
        echo $n; ((n++));
        ./nbd-fault-injector.py 127.0.0.1:10000 nbd-fault-injector.conf;
    done
    
    3. In another terminal run qemu-io in a loop, like this:
    
    n=1; while true; do
        echo $n; ((n++));
        ./qemu-io -c 'read 0 512' nbd://127.0.0.1:10000;
    done
    
    After some time, qemu-io will hang. Note, that this hang may be
    triggered by another bug, so the whole case is fixed only together with
    commit "block/nbd: allow drain during reconnect attempt".
    
    Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@xxxxxxxxxxxxx>
    Reviewed-by: Eric Blake <eblake@xxxxxxxxxx>
    Message-Id: <20200727184751.15704-4-vsementsov@xxxxxxxxxxxxx>
    Signed-off-by: Eric Blake <eblake@xxxxxxxxxx>
---
 block/nbd.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index ee9ab7512b..620c97be6b 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -209,11 +209,15 @@ static void nbd_teardown_connection(BlockDriverState *bs)
 {
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
 
-    if (s->state == NBD_CLIENT_CONNECTED) {
+    if (s->ioc) {
         /* finish any pending coroutines */
-        assert(s->ioc);
         qio_channel_shutdown(s->ioc, QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
+    } else if (s->sioc) {
+        /* abort negotiation */
+        qio_channel_shutdown(QIO_CHANNEL(s->sioc), QIO_CHANNEL_SHUTDOWN_BOTH,
+                             NULL);
     }
+
     s->state = NBD_CLIENT_QUIT;
     if (s->connection_co) {
         if (s->connection_co_sleep_ns_state) {
@@ -1459,6 +1463,9 @@ static int nbd_client_handshake(BlockDriverState *bs, 
QIOChannelSocket *sioc,
     int ret;
 
     trace_nbd_client_handshake(s->export);
+
+    s->sioc = sioc;
+
     qio_channel_set_blocking(QIO_CHANNEL(sioc), false, NULL);
     qio_channel_attach_aio_context(QIO_CHANNEL(sioc), aio_context);
 
@@ -1473,6 +1480,7 @@ static int nbd_client_handshake(BlockDriverState *bs, 
QIOChannelSocket *sioc,
     g_free(s->info.name);
     if (ret < 0) {
         object_unref(OBJECT(sioc));
+        s->sioc = NULL;
         return ret;
     }
     if (s->x_dirty_bitmap && !s->info.base_allocation) {
@@ -1498,8 +1506,6 @@ static int nbd_client_handshake(BlockDriverState *bs, 
QIOChannelSocket *sioc,
         }
     }
 
-    s->sioc = sioc;
-
     if (!s->ioc) {
         s->ioc = QIO_CHANNEL(sioc);
         object_ref(OBJECT(s->ioc));
@@ -1520,6 +1526,7 @@ static int nbd_client_handshake(BlockDriverState *bs, 
QIOChannelSocket *sioc,
         nbd_send_request(s->ioc ?: QIO_CHANNEL(sioc), &request);
 
         object_unref(OBJECT(sioc));
+        s->sioc = NULL;
 
         return ret;
     }
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#staging