block/nbd: Move s->ioc on AioContext change

s->ioc must always be attached to the NBD node's AioContext.  If that
context changes, s->ioc must be attached to the new context.

Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2033626
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>

block/nbd.c

@@ -2055,6 +2055,42 @@ static void nbd_cancel_in_flight(BlockDriverState *bs)
     nbd_co_establish_connection_cancel(s->conn);
 }
 
+static void nbd_attach_aio_context(BlockDriverState *bs,
+                                   AioContext *new_context)
+{
+    BDRVNBDState *s = bs->opaque;
+
+    /* The open_timer is used only during nbd_open() */
+    assert(!s->open_timer);
+
+    /*
+     * The reconnect_delay_timer is scheduled in I/O paths when the
+     * connection is lost, to cancel the reconnection attempt after a
+     * given time.  Once this attempt is done (successfully or not),
+     * nbd_reconnect_attempt() ensures the timer is deleted before the
+     * respective I/O request is resumed.
+     * Since the AioContext can only be changed when a node is drained,
+     * the reconnect_delay_timer cannot be active here.
+     */
+    assert(!s->reconnect_delay_timer);
+
+    if (s->ioc) {
+        qio_channel_attach_aio_context(s->ioc, new_context);
+    }
+}
+
+static void nbd_detach_aio_context(BlockDriverState *bs)
+{
+    BDRVNBDState *s = bs->opaque;
+
+    assert(!s->open_timer);
+    assert(!s->reconnect_delay_timer);
+
+    if (s->ioc) {
+        qio_channel_detach_aio_context(s->ioc);
+    }
+}
+
 static BlockDriver bdrv_nbd = {
     .format_name                = "nbd",
     .protocol_name              = "nbd",
@@ -2078,6 +2114,9 @@ static BlockDriver bdrv_nbd = {
     .bdrv_dirname               = nbd_dirname,
     .strong_runtime_opts        = nbd_strong_runtime_opts,
     .bdrv_cancel_in_flight      = nbd_cancel_in_flight,
+
+    .bdrv_attach_aio_context    = nbd_attach_aio_context,
+    .bdrv_detach_aio_context    = nbd_detach_aio_context,
 };
 
 static BlockDriver bdrv_nbd_tcp = {
@@ -2103,6 +2142,9 @@ static BlockDriver bdrv_nbd_tcp = {
     .bdrv_dirname               = nbd_dirname,
     .strong_runtime_opts        = nbd_strong_runtime_opts,
     .bdrv_cancel_in_flight      = nbd_cancel_in_flight,
+
+    .bdrv_attach_aio_context    = nbd_attach_aio_context,
+    .bdrv_detach_aio_context    = nbd_detach_aio_context,
 };
 
 static BlockDriver bdrv_nbd_unix = {
@@ -2128,6 +2170,9 @@ static BlockDriver bdrv_nbd_unix = {
     .bdrv_dirname               = nbd_dirname,
     .strong_runtime_opts        = nbd_strong_runtime_opts,
     .bdrv_cancel_in_flight      = nbd_cancel_in_flight,
+
+    .bdrv_attach_aio_context    = nbd_attach_aio_context,
+    .bdrv_detach_aio_context    = nbd_detach_aio_context,
 };
 
 static void bdrv_nbd_init(void)