[Qemu-devel] [PATCH] virtio-scsi-dataplane: Add op blocker

[Fam Zheng <famz@redhat.com>]

We need this to protect dataplane thread from race conditions with block
jobs until the latter is made dataplane-safe.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 hw/scsi/virtio-scsi-dataplane.c |  4 ++++
 hw/scsi/virtio-scsi.c           | 19 +++++++++++++++++--
 include/hw/virtio/virtio-scsi.h |  1 +
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c
index b778e05..97c2a4f 100644
--- a/hw/scsi/virtio-scsi-dataplane.c
+++ b/hw/scsi/virtio-scsi-dataplane.c
@@ -154,6 +154,8 @@ void virtio_scsi_dataplane_start(VirtIOSCSI *s)
 
     s->dataplane_starting = true;
 
+    assert(!s->blocker);
+    error_setg(&s->blocker, "block device is in use by data plane");
     /* Set up guest notifier (irq) */
     rc = k->set_guest_notifiers(qbus->parent, vs->conf.num_queues + 2, true);
     if (rc != 0) {
@@ -194,6 +196,8 @@ void virtio_scsi_dataplane_stop(VirtIOSCSI *s)
     if (!s->dataplane_started || s->dataplane_stopping) {
         return;
     }
+    error_free(s->blocker);
+    s->blocker = NULL;
     s->dataplane_stopping = true;
     assert(s->ctx == iothread_get_aio_context(vs->conf.iothread));
 
diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index 8547ea0..99fddee 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -741,9 +741,18 @@ static void virtio_scsi_hotplug(HotplugHandler *hotplug_dev, DeviceState *dev,
                                 Error **errp)
 {
     VirtIODevice *vdev = VIRTIO_DEVICE(hotplug_dev);
+    VirtIOSCSI *s = VIRTIO_SCSI(vdev);
+    SCSIDevice *sd = SCSI_DEVICE(dev);
+
+    if (s->ctx && !s->dataplane_disabled) {
+        if (bdrv_op_is_blocked(sd->conf.bs, BLOCK_OP_TYPE_DATAPLANE, errp)) {
+            return;
+        }
+        bdrv_op_block_all(sd->conf.bs, s->blocker);
+    }
 
     if ((vdev->guest_features >> VIRTIO_SCSI_F_HOTPLUG) & 1) {
-        virtio_scsi_push_event(VIRTIO_SCSI(hotplug_dev), SCSI_DEVICE(dev),
+        virtio_scsi_push_event(s, sd,
                                VIRTIO_SCSI_T_TRANSPORT_RESET,
                                VIRTIO_SCSI_EVT_RESET_RESCAN);
     }
@@ -753,12 +762,18 @@ static void virtio_scsi_hotunplug(HotplugHandler *hotplug_dev, DeviceState *dev,
                                   Error **errp)
 {
     VirtIODevice *vdev = VIRTIO_DEVICE(hotplug_dev);
+    VirtIOSCSI *s = VIRTIO_SCSI(vdev);
+    SCSIDevice *sd = SCSI_DEVICE(dev);
 
     if ((vdev->guest_features >> VIRTIO_SCSI_F_HOTPLUG) & 1) {
-        virtio_scsi_push_event(VIRTIO_SCSI(hotplug_dev), SCSI_DEVICE(dev),
+        virtio_scsi_push_event(s, sd,
                                VIRTIO_SCSI_T_TRANSPORT_RESET,
                                VIRTIO_SCSI_EVT_RESET_REMOVED);
     }
+
+    if (s->ctx) {
+        bdrv_op_unblock_all(sd->conf.bs, s->blocker);
+    }
     qdev_simple_device_unplug_cb(hotplug_dev, dev, errp);
 }
 
diff --git a/include/hw/virtio/virtio-scsi.h b/include/hw/virtio/virtio-scsi.h
index d6e5e79..1ce0858 100644
--- a/include/hw/virtio/virtio-scsi.h
+++ b/include/hw/virtio/virtio-scsi.h
@@ -195,6 +195,7 @@ typedef struct VirtIOSCSI {
     bool dataplane_starting;
     bool dataplane_stopping;
     bool dataplane_disabled;
+    Error *blocker;
     Notifier migration_state_notifier;
 } VirtIOSCSI;
 
-- 
1.9.3