[PATCH 2/2] virtio-blk: replace dataplane_start/stopping/started with enum

[Emanuele Giuseppe Esposito]

Virtio-blk uses VirtIOBlockDataPlane and VirtIOBlock to keep track of
the dataplane flags. This is completely unnecessary, as both structures
are always accessed together and we can simplify the sages with an enum.

Read/write the enum atomically, as it can be read also by iothread
callbacks.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
 hw/block/dataplane/virtio-blk.c | 24 +++++++++---------------
 hw/block/virtio-blk.c           |  9 +++++----
 include/hw/virtio/virtio-blk.h  |  2 +-
 3 files changed, 15 insertions(+), 20 deletions(-)

diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index 49276e46f2..427f946859 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -27,9 +27,6 @@
 #include "qom/object_interfaces.h"
 
 struct VirtIOBlockDataPlane {
-    bool starting;
-    bool stopping;
-
     VirtIOBlkConf *conf;
     VirtIODevice *vdev;
     QEMUBH *bh;                     /* bh for guest notification */
@@ -145,7 +142,7 @@ void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
     }
 
     vblk = VIRTIO_BLK(s->vdev);
-    assert(!vblk->dataplane_started);
+    assert(qatomic_read(&vblk->dataplane_state) != DATAPLANE_STARTED);
     g_free(s->batch_notify_vqs);
     qemu_bh_delete(s->bh);
     if (s->iothread) {
@@ -167,11 +164,11 @@ int virtio_blk_data_plane_start(VirtIODevice *vdev)
     Error *local_err = NULL;
     int r;
 
-    if (vblk->dataplane_started || s->starting) {
+    if (qatomic_read(&vblk->dataplane_state) <= DATAPLANE_STARTED) {
         return 0;
     }
 
-    s->starting = true;
+    qatomic_set(&vblk->dataplane_state, DATAPLANE_STARTING);
 
     if (!virtio_vdev_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX)) {
         s->batch_notifications = true;
@@ -219,8 +216,7 @@ int virtio_blk_data_plane_start(VirtIODevice *vdev)
 
     memory_region_transaction_commit();
 
-    s->starting = false;
-    vblk->dataplane_started = true;
+    qatomic_set(&vblk->dataplane_state, DATAPLANE_STARTED);
     trace_virtio_blk_data_plane_start(s);
 
     old_context = blk_get_aio_context(s->conf->conf.blk);
@@ -273,8 +269,7 @@ int virtio_blk_data_plane_start(VirtIODevice *vdev)
      */
     virtio_blk_process_queued_requests(vblk, false);
     vblk->dataplane_disabled = true;
-    s->starting = false;
-    vblk->dataplane_started = true;
+    qatomic_set(&vblk->dataplane_state, DATAPLANE_STARTED);
     return -ENOSYS;
 }
 
@@ -304,17 +299,17 @@ void virtio_blk_data_plane_stop(VirtIODevice *vdev)
     unsigned i;
     unsigned nvqs = s->conf->num_queues;
 
-    if (!vblk->dataplane_started || s->stopping) {
+    if (qatomic_read(&vblk->dataplane_state) != DATAPLANE_STARTED) {
         return;
     }
 
     /* Better luck next time. */
     if (vblk->dataplane_disabled) {
         vblk->dataplane_disabled = false;
-        vblk->dataplane_started = false;
+        qatomic_set(&vblk->dataplane_state, DATAPLANE_STOPPED);
         return;
     }
-    s->stopping = true;
+    qatomic_set(&vblk->dataplane_state, DATAPLANE_STOPPING);
     trace_virtio_blk_data_plane_stop(s);
 
     aio_context_acquire(s->ctx);
@@ -352,6 +347,5 @@ void virtio_blk_data_plane_stop(VirtIODevice *vdev)
     /* Clean up guest notifier (irq) */
     k->set_guest_notifiers(qbus->parent, nvqs, false);
 
-    vblk->dataplane_started = false;
-    s->stopping = false;
+    qatomic_set(&vblk->dataplane_state, DATAPLANE_STOPPED);
 }
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index e9ba752f6b..a53c4a1063 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -84,7 +84,8 @@ static void virtio_blk_req_complete(VirtIOBlockReq *req, 
unsigned char status)
     iov_discard_undo(&req->inhdr_undo);
     iov_discard_undo(&req->outhdr_undo);
     virtqueue_push(req->vq, &req->elem, req->in_len);
-    if (s->dataplane_started && !s->dataplane_disabled) {
+    if (qatomic_read(&s->dataplane_state) == DATAPLANE_STARTED &&
+        !s->dataplane_disabled) {
         virtio_blk_data_plane_notify(s->dataplane, req->vq);
     } else {
         virtio_notify(vdev, req->vq);
@@ -807,7 +808,7 @@ static void virtio_blk_handle_output(VirtIODevice *vdev, 
VirtQueue *vq)
 {
     VirtIOBlock *s = (VirtIOBlock *)vdev;
 
-    if (s->dataplane && !s->dataplane_started) {
+    if (s->dataplane && qatomic_read(&s->dataplane_state) > DATAPLANE_STARTED) 
{
         /* Some guests kick before setting VIRTIO_CONFIG_S_DRIVER_OK so start
          * dataplane here instead of waiting for .set_status().
          */
@@ -907,7 +908,7 @@ static void virtio_blk_reset(VirtIODevice *vdev)
 
     aio_context_release(ctx);
 
-    assert(!s->dataplane_started);
+    assert(qatomic_read(&s->dataplane_state) != DATAPLANE_STARTED);
     blk_set_enable_write_cache(s->blk, s->original_wce);
 }
 
@@ -1033,7 +1034,7 @@ static void virtio_blk_set_status(VirtIODevice *vdev, 
uint8_t status)
     VirtIOBlock *s = VIRTIO_BLK(vdev);
 
     if (!(status & (VIRTIO_CONFIG_S_DRIVER | VIRTIO_CONFIG_S_DRIVER_OK))) {
-        assert(!s->dataplane_started);
+        assert(qatomic_read(&s->dataplane_state) != DATAPLANE_STARTED);
     }
 
     if (!(status & VIRTIO_CONFIG_S_DRIVER_OK)) {
diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
index d311c57cca..3ac66a1f77 100644
--- a/include/hw/virtio/virtio-blk.h
+++ b/include/hw/virtio/virtio-blk.h
@@ -60,7 +60,7 @@ struct VirtIOBlock {
     bool original_wce;
     VMChangeStateEntry *change;
     bool dataplane_disabled;
-    bool dataplane_started;
+    enum VirtIODataplaneStates dataplane_state;
     struct VirtIOBlockDataPlane *dataplane;
     uint64_t host_features;
     size_t config_size;
-- 
2.31.1