[PATCH v2 2/2] vhost-user: fix lost reconnect again

[Li Feng]

When the vhost-user is reconnecting to the backend, and if the vhost-user fails
at the get_features in vhost_dev_init(), then the reconnect will fail
and it will not be retriggered forever.

The reason is:
When the vhost-user fail at get_features, the vhost_dev_cleanup will be called
immediately.

vhost_dev_cleanup calls 'memset(hdev, 0, sizeof(struct vhost_dev))'.

The reconnect path is:
vhost_user_blk_event
   vhost_user_async_close(.. vhost_user_blk_disconnect ..)
     qemu_chr_fe_set_handlers <----- clear the notifier callback
       schedule vhost_user_async_close_bh

The vhost->vdev is null, so the vhost_user_blk_disconnect will not be
called, then the event fd callback will not be reinstalled.

With this patch, the vhost_user_blk_disconnect will call the
vhost_dev_cleanup() again, it's safe.

In addition, the CLOSE event may occur in a scenario where connected is false.
At this time, the event handler will be cleared. We need to ensure that the
event handler can remain installed.

All vhost-user devices have this issue, including vhost-user-blk/scsi.

Fixes: 71e076a07d ("hw/virtio: generalise CHR_EVENT_CLOSED handling")

Signed-off-by: Li Feng <fengli@smartx.com>
---
 hw/block/vhost-user-blk.c   |  3 ++-
 hw/scsi/vhost-user-scsi.c   |  3 ++-
 hw/virtio/vhost-user-base.c |  3 ++-
 hw/virtio/vhost-user.c      | 10 +---------
 4 files changed, 7 insertions(+), 12 deletions(-)

diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index 41d1ac3a5a..c6842ced48 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -353,7 +353,7 @@ static void vhost_user_blk_disconnect(DeviceState *dev)
     VHostUserBlk *s = VHOST_USER_BLK(vdev);
 
     if (!s->connected) {
-        return;
+        goto done;
     }
     s->connected = false;
 
@@ -361,6 +361,7 @@ static void vhost_user_blk_disconnect(DeviceState *dev)
 
     vhost_dev_cleanup(&s->dev);
 
+done:
     /* Re-instate the event handler for new connections */
     qemu_chr_fe_set_handlers(&s->chardev, NULL, NULL, vhost_user_blk_event,
                              NULL, dev, NULL, true);
diff --git a/hw/scsi/vhost-user-scsi.c b/hw/scsi/vhost-user-scsi.c
index 48a59e020e..b49a11d23b 100644
--- a/hw/scsi/vhost-user-scsi.c
+++ b/hw/scsi/vhost-user-scsi.c
@@ -181,7 +181,7 @@ static void vhost_user_scsi_disconnect(DeviceState *dev)
     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(dev);
 
     if (!s->connected) {
-        return;
+        goto done;
     }
     s->connected = false;
 
@@ -189,6 +189,7 @@ static void vhost_user_scsi_disconnect(DeviceState *dev)
 
     vhost_dev_cleanup(&vsc->dev);
 
+done:
     /* Re-instate the event handler for new connections */
     qemu_chr_fe_set_handlers(&vs->conf.chardev, NULL, NULL,
                              vhost_user_scsi_event, NULL, dev, NULL, true);
diff --git a/hw/virtio/vhost-user-base.c b/hw/virtio/vhost-user-base.c
index 4b54255682..11e72b1e3b 100644
--- a/hw/virtio/vhost-user-base.c
+++ b/hw/virtio/vhost-user-base.c
@@ -225,13 +225,14 @@ static void vub_disconnect(DeviceState *dev)
     VHostUserBase *vub = VHOST_USER_BASE(vdev);
 
     if (!vub->connected) {
-        return;
+        goto done;
     }
     vub->connected = false;
 
     vub_stop(vdev);
     vhost_dev_cleanup(&vub->vhost_dev);
 
+done:
     /* Re-instate the event handler for new connections */
     qemu_chr_fe_set_handlers(&vub->chardev,
                              NULL, NULL, vub_event,
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index c929097e87..c407ea8939 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -2781,16 +2781,8 @@ typedef struct {
 static void vhost_user_async_close_bh(void *opaque)
 {
     VhostAsyncCallback *data = opaque;
-    struct vhost_dev *vhost = data->vhost;
 
-    /*
-     * If the vhost_dev has been cleared in the meantime there is
-     * nothing left to do as some other path has completed the
-     * cleanup.
-     */
-    if (vhost->vdev) {
-        data->cb(data->dev);
-    }
+    data->cb(data->dev);
 
     g_free(data);
 }
-- 
2.45.0