nbd: Remove NBDExport.close callback

The export close callback is unused by the built-in NBD server. qemu-nbd
uses it only during shutdown to wait for the unrefed export to actually
go away. It can just use nbd_export_close_all() instead and do without
the callback.

This removes the close callback from nbd_export_new() and makes both
callers of it more similar.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200924152717.287415-11-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/qemu-nbd.c b/qemu-nbd.c
index b2a0ea6..abbed8f 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -70,7 +70,7 @@
 static char *srcpath;
 static SocketAddress *saddr;
 static int persistent = 0;
-static enum { RUNNING, TERMINATE, TERMINATING, TERMINATED } state;
+static enum { RUNNING, TERMINATE, TERMINATED } state;
 static int shared = 1;
 static int nb_fds;
 static QIONetListener *server;
@@ -332,12 +332,6 @@
     return state == RUNNING && nb_fds < shared;
 }
 
-static void nbd_export_closed(NBDExport *export)
-{
-    assert(state == TERMINATING);
-    state = TERMINATED;
-}
-
 static void nbd_update_server_watch(void);
 
 static void nbd_client_closed(NBDClient *client, bool negotiated)
@@ -1067,7 +1061,7 @@
 
     export = nbd_export_new(bs, export_name,
                             export_description, bitmap, readonly, shared > 1,
-                            nbd_export_closed, writethrough, &error_fatal);
+                            writethrough, &error_fatal);
 
     if (device) {
 #if HAVE_NBD_DEVICE
@@ -1107,10 +1101,10 @@
     do {
         main_loop_wait(false);
         if (state == TERMINATE) {
-            state = TERMINATING;
-            nbd_export_close(export);
             nbd_export_put(export);
+            nbd_export_close_all();
             export = NULL;
+            state = TERMINATED;
         }
     } while (state != TERMINATED);