Merge tag 'pull-nbd-2023-09-07-v2' of https://repo.or.cz/qemu/ericb into staging

NBD patches for 2023-09-07

- Andrey Drobyshev - fix regression in iotest 197 under -nbd
- Stefan Hajnoczi - allow coroutine read and write context to split
across threads
- Philippe Mathieu-Daudé - remove a VLA allocation
- Denis V. Lunev - fix regression in iotest 233 with qemu-nbd -v --fork

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* tag 'pull-nbd-2023-09-07-v2' of https://repo.or.cz/qemu/ericb:
  qemu-nbd: document -v behavior in respect to --fork in man
  qemu-nbd: Restore "qemu-nbd -v --fork" output
  qemu-nbd: invent nbd_client_release_pipe() helper
  qemu-nbd: put saddr into into struct NbdClientOpts
  qemu-nbd: move srcpath into struct NbdClientOpts
  qemu-nbd: define struct NbdClientOpts when HAVE_NBD_DEVICE is not defined
  qemu-nbd: improve error message for dup2 error
  util/iov: Avoid dynamic stack allocation
  io: follow coroutine AioContext in qio_channel_yield()
  io: check there are no qio_channel_yield() coroutines during ->finalize()
  nbd: drop unused nbd_start_negotiate() aio_context argument
  nbd: drop unused nbd_receive_negotiate() aio_context argument
  qemu-iotests/197: use more generic commands for formats other than qcow2

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 20 insertions, 7 deletions

diff --git a/util/vhost-user-server.c b/util/vhost-user-server.c
index cd17fb5326..b4b6bf30a2 100644
--- a/util/vhost-user-server.c
+++ b/util/vhost-user-server.c
@@ -127,7 +127,14 @@ vu_message_read(VuDev *vu_dev, int conn_fd, VhostUserMsg *vmsg)
         if (rc < 0) {
             if (rc == QIO_CHANNEL_ERR_BLOCK) {
                 assert(local_err == NULL);
-                qio_channel_yield(ioc, G_IO_IN);
+                if (server->ctx) {
+                    server->in_qio_channel_yield = true;
+                    qio_channel_yield(ioc, G_IO_IN);
+                    server->in_qio_channel_yield = false;
+                } else {
+                    /* Wait until attached to an AioContext again */
+                    qemu_coroutine_yield();
+                }
                 continue;
             } else {
                 error_report_err(local_err);
@@ -278,7 +285,7 @@ set_watch(VuDev *vu_dev, int fd, int vu_evt,
         vu_fd_watch->fd = fd;
         vu_fd_watch->cb = cb;
         qemu_socket_set_nonblock(fd);
-        aio_set_fd_handler(server->ioc->ctx, fd, kick_handler,
+        aio_set_fd_handler(server->ctx, fd, kick_handler,
                            NULL, NULL, NULL, vu_fd_watch);
         vu_fd_watch->vu_dev = vu_dev;
         vu_fd_watch->pvt = pvt;
@@ -299,7 +306,7 @@ static void remove_watch(VuDev *vu_dev, int fd)
     if (!vu_fd_watch) {
         return;
     }
-    aio_set_fd_handler(server->ioc->ctx, fd, NULL, NULL, NULL, NULL, NULL);
+    aio_set_fd_handler(server->ctx, fd, NULL, NULL, NULL, NULL, NULL);
 
     QTAILQ_REMOVE(&server->vu_fd_watches, vu_fd_watch, next);
     g_free(vu_fd_watch);
@@ -344,6 +351,8 @@ static void vu_accept(QIONetListener *listener, QIOChannelSocket *sioc,
     /* TODO vu_message_write() spins if non-blocking! */
     qio_channel_set_blocking(server->ioc, false, NULL);
 
+    qio_channel_set_follow_coroutine_ctx(server->ioc, true);
+
     server->co_trip = qemu_coroutine_create(vu_client_trip, server);
 
     aio_context_acquire(server->ctx);
@@ -399,13 +408,12 @@ void vhost_user_server_attach_aio_context(VuServer *server, AioContext *ctx)
         return;
     }
 
-    qio_channel_attach_aio_context(server->ioc, ctx);
-
     QTAILQ_FOREACH(vu_fd_watch, &server->vu_fd_watches, next) {
         aio_set_fd_handler(ctx, vu_fd_watch->fd, kick_handler, NULL,
                            NULL, NULL, vu_fd_watch);
     }
 
+    assert(!server->in_qio_channel_yield);
     aio_co_schedule(ctx, server->co_trip);
 }
 
@@ -419,11 +427,16 @@ void vhost_user_server_detach_aio_context(VuServer *server)
             aio_set_fd_handler(server->ctx, vu_fd_watch->fd,
                                NULL, NULL, NULL, NULL, vu_fd_watch);
         }
-
-        qio_channel_detach_aio_context(server->ioc);
     }
 
     server->ctx = NULL;
+
+    if (server->ioc) {
+        if (server->in_qio_channel_yield) {
+            /* Stop receiving the next vhost-user message */
+            qio_channel_wake_read(server->ioc);
+        }
+    }
 }
 
 bool vhost_user_server_start(VuServer *server,