Merge tag 'for-upstream' of https://repo.or.cz/qemu/kevin into staging

Block layer patches

- aio-posix: Fix race during epoll upgrade
- vhost-user-blk/VDUSE export: Fix a potential deadlock and an assertion
  failure when the export runs in an iothread
- NBD server: Push pending frames after sending reply to fix performance
  especially when used with TLS

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* tag 'for-upstream' of https://repo.or.cz/qemu/kevin:
  block/export: Fix graph locking in blk_get_geometry() call
  aio-posix: fix race between epoll upgrade and aio_set_fd_handler()
  block/export: only acquire AioContext once for vhost_user_server_stop()
  nbd/server: push pending frames after sending reply

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

2 files changed, 19 insertions, 11 deletions

diff --git a/util/fdmon-epoll.c b/util/fdmon-epoll.c
index e11a8a02..1683aa1 100644
--- a/util/fdmon-epoll.c
+++ b/util/fdmon-epoll.c
@@ -127,6 +127,8 @@ static bool fdmon_epoll_try_enable(AioContext *ctx)
 
 bool fdmon_epoll_try_upgrade(AioContext *ctx, unsigned npfd)
 {
+    bool ok;
+
     if (ctx->epollfd < 0) {
         return false;
     }
@@ -136,14 +138,23 @@ bool fdmon_epoll_try_upgrade(AioContext *ctx, unsigned npfd)
         return false;
     }
 
-    if (npfd >= EPOLL_ENABLE_THRESHOLD) {
-        if (fdmon_epoll_try_enable(ctx)) {
-            return true;
-        } else {
-            fdmon_epoll_disable(ctx);
-        }
+    if (npfd < EPOLL_ENABLE_THRESHOLD) {
+        return false;
+    }
+
+    /* The list must not change while we add fds to epoll */
+    if (!qemu_lockcnt_dec_if_lock(&ctx->list_lock)) {
+        return false;
+    }
+
+    ok = fdmon_epoll_try_enable(ctx);
+
+    qemu_lockcnt_inc_and_unlock(&ctx->list_lock);
+
+    if (!ok) {
+        fdmon_epoll_disable(ctx);
     }
-    return false;
+    return ok;
 }
 
 void fdmon_epoll_setup(AioContext *ctx)
diff --git a/util/vhost-user-server.c b/util/vhost-user-server.c
index 40f36ea..5b62160 100644
--- a/util/vhost-user-server.c
+++ b/util/vhost-user-server.c
@@ -346,10 +346,9 @@ static void vu_accept(QIONetListener *listener, QIOChannelSocket *sioc,
     aio_context_release(server->ctx);
 }
 
+/* server->ctx acquired by caller */
 void vhost_user_server_stop(VuServer *server)
 {
-    aio_context_acquire(server->ctx);
-
     qemu_bh_delete(server->restart_listener_bh);
     server->restart_listener_bh = NULL;
 
@@ -366,8 +365,6 @@ void vhost_user_server_stop(VuServer *server)
         AIO_WAIT_WHILE(server->ctx, server->co_trip);
     }
 
-    aio_context_release(server->ctx);
-
     if (server->listener) {
         qio_net_listener_disconnect(server->listener);
         object_unref(OBJECT(server->listener));