[PATCH 2/2] virtio_balloon: Treat stats requests as wakeup events

[David Stevens]

From: David Stevens <steve...@chromium.org>

Treat stats requests as wakeup events to ensure that the driver responds
to device requests in a timely manner.

Signed-off-by: David Stevens <steve...@chromium.org>
---
 drivers/virtio/virtio_balloon.c | 75 ++++++++++++++++++++-------------
 1 file changed, 46 insertions(+), 29 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 7fe7ef5f1c77..402dec98e08c 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -121,11 +121,14 @@ struct virtio_balloon {
        struct page_reporting_dev_info pr_dev_info;
 
        /* State for keeping the wakeup_source active while adjusting the 
balloon */
-       spinlock_t adjustment_lock;
-       bool adjustment_signal_pending;
-       bool adjustment_in_progress;
+       spinlock_t wakeup_lock;
+       bool processing_wakeup_event;
+       u32 wakeup_signal_mask;
 };
 
+#define ADJUSTMENT_WAKEUP_SIGNAL (1 << 0)
+#define STATS_WAKEUP_SIGNAL (1 << 1)
+
 static const struct virtio_device_id id_table[] = {
        { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
        { 0 },
@@ -140,6 +143,36 @@ static u32 page_to_balloon_pfn(struct page *page)
        return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
 }
 
+static void start_wakeup_event(struct virtio_balloon *vb, u32 mask)
+{
+       unsigned long flags;
+
+       spin_lock_irqsave(&vb->wakeup_lock, flags);
+       vb->wakeup_signal_mask |= mask;
+       if (!vb->processing_wakeup_event) {
+               vb->processing_wakeup_event = true;
+               pm_stay_awake(&vb->vdev->dev);
+       }
+       spin_unlock_irqrestore(&vb->wakeup_lock, flags);
+}
+
+static void process_wakeup_event(struct virtio_balloon *vb, u32 mask)
+{
+       spin_lock_irq(&vb->wakeup_lock);
+       vb->wakeup_signal_mask &= ~mask;
+       spin_unlock_irq(&vb->wakeup_lock);
+}
+
+static void finish_wakeup_event(struct virtio_balloon *vb)
+{
+       spin_lock_irq(&vb->wakeup_lock);
+       if (!vb->wakeup_signal_mask && vb->processing_wakeup_event) {
+               vb->processing_wakeup_event = false;
+               pm_relax(&vb->vdev->dev);
+       }
+       spin_unlock_irq(&vb->wakeup_lock);
+}
+
 static void balloon_ack(struct virtqueue *vq)
 {
        struct virtio_balloon *vb = vq->vdev->priv;
@@ -370,8 +403,10 @@ static void stats_request(struct virtqueue *vq)
        struct virtio_balloon *vb = vq->vdev->priv;
 
        spin_lock(&vb->stop_update_lock);
-       if (!vb->stop_update)
+       if (!vb->stop_update) {
+               start_wakeup_event(vb, STATS_WAKEUP_SIGNAL);
                queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
+       }
        spin_unlock(&vb->stop_update_lock);
 }
 
@@ -444,29 +479,10 @@ static void virtio_balloon_queue_free_page_work(struct 
virtio_balloon *vb)
 
 static void start_update_balloon_size(struct virtio_balloon *vb)
 {
-       unsigned long flags;
-
-       spin_lock_irqsave(&vb->adjustment_lock, flags);
-       vb->adjustment_signal_pending = true;
-       if (!vb->adjustment_in_progress) {
-               vb->adjustment_in_progress = true;
-               pm_stay_awake(&vb->vdev->dev);
-       }
-       spin_unlock_irqrestore(&vb->adjustment_lock, flags);
-
+       start_wakeup_event(vb, ADJUSTMENT_WAKEUP_SIGNAL);
        queue_work(system_freezable_wq, &vb->update_balloon_size_work);
 }
 
-static void end_update_balloon_size(struct virtio_balloon *vb)
-{
-       spin_lock_irq(&vb->adjustment_lock);
-       if (!vb->adjustment_signal_pending && vb->adjustment_in_progress) {
-               vb->adjustment_in_progress = false;
-               pm_relax(&vb->vdev->dev);
-       }
-       spin_unlock_irq(&vb->adjustment_lock);
-}
-
 static void virtballoon_changed(struct virtio_device *vdev)
 {
        struct virtio_balloon *vb = vdev->priv;
@@ -495,7 +511,10 @@ static void update_balloon_stats_func(struct work_struct 
*work)
 
        vb = container_of(work, struct virtio_balloon,
                          update_balloon_stats_work);
+
+       process_wakeup_event(vb, STATS_WAKEUP_SIGNAL);
        stats_handle_request(vb);
+       finish_wakeup_event(vb);
 }
 
 static void update_balloon_size_func(struct work_struct *work)
@@ -506,9 +525,7 @@ static void update_balloon_size_func(struct work_struct 
*work)
        vb = container_of(work, struct virtio_balloon,
                          update_balloon_size_work);
 
-       spin_lock_irq(&vb->adjustment_lock);
-       vb->adjustment_signal_pending = false;
-       spin_unlock_irq(&vb->adjustment_lock);
+       process_wakeup_event(vb, ADJUSTMENT_WAKEUP_SIGNAL);
 
        diff = towards_target(vb);
 
@@ -523,7 +540,7 @@ static void update_balloon_size_func(struct work_struct 
*work)
        if (diff)
                queue_work(system_freezable_wq, work);
        else
-               end_update_balloon_size(vb);
+               finish_wakeup_event(vb);
 }
 
 static int init_vqs(struct virtio_balloon *vb)
@@ -1027,7 +1044,7 @@ static int virtballoon_probe(struct virtio_device *vdev)
                        goto out_unregister_oom;
        }
 
-       spin_lock_init(&vb->adjustment_lock);
+       spin_lock_init(&vb->wakeup_lock);
        device_set_wakeup_capable(&vb->vdev->dev, true);
 
        virtio_device_ready(vdev);
-- 
2.44.0.291.gc1ea87d7ee-goog