[PATCH v4 5/6] virtio-balloon: Pull page poisoning config out of free page hinting

[Alexander Duyck <alexander.duyck@xxxxxxxxx>]

From: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>

Currently the page poisoning setting wasn't being enabled unless free page
hinting was enabled. However we will need the page poisoning tracking logic
as well for unused page reporting. As such pull it out and make it a
separate bit of config in the probe function.

In addition we can actually wrap the code in a check for NO_SANITY. If we
don't care what is actually in the page we can just default to 0 and leave
it there.

Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
---
 drivers/virtio/virtio_balloon.c |   19 +++++++++++++------
 mm/page_reporting.c             |    8 ++++----
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 226fbb995fb0..2c19457ab573 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -842,7 +842,6 @@ static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
 static int virtballoon_probe(struct virtio_device *vdev)
 {
 	struct virtio_balloon *vb;
-	__u32 poison_val;
 	int err;
 
 	if (!vdev->config->get) {
@@ -909,11 +908,19 @@ static int virtballoon_probe(struct virtio_device *vdev)
 						  VIRTIO_BALLOON_CMD_ID_STOP);
 		spin_lock_init(&vb->free_page_list_lock);
 		INIT_LIST_HEAD(&vb->free_page_list);
-		if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
-			memset(&poison_val, PAGE_POISON, sizeof(poison_val));
-			virtio_cwrite(vb->vdev, struct virtio_balloon_config,
-				      poison_val, &poison_val);
-		}
+	}
+	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
+		__u32 poison_val = 0;
+
+#if !defined(CONFIG_PAGE_POISONING_NO_SANITY)
+		/*
+		 * Let hypervisor know that we are expecting a specific
+		 * value to be written back in unused pages.
+		 */
+		memset(&poison_val, PAGE_POISON, sizeof(poison_val));
+#endif
+		virtio_cwrite(vb->vdev, struct virtio_balloon_config,
+			      poison_val, &poison_val);
 	}
 	/*
 	 * We continue to use VIRTIO_BALLOON_F_DEFLATE_ON_OOM to decide if a
diff --git a/mm/page_reporting.c b/mm/page_reporting.c
index ae26dd77bce9..68dccfc7d629 100644
--- a/mm/page_reporting.c
+++ b/mm/page_reporting.c
@@ -250,7 +250,7 @@ void __page_reporting_free_stats(struct zone *zone)
 
 void page_reporting_shutdown(struct page_reporting_dev_info *phdev)
 {
-	mutex_lock(page_reporting_mutex);
+	mutex_lock(&page_reporting_mutex);
 
 	if (rcu_access_pointer(ph_dev_info) == phdev) {
 		/* Disable page reporting notification */
@@ -266,7 +266,7 @@ void page_reporting_shutdown(struct page_reporting_dev_info *phdev)
 		phdev->sg = NULL;
 	}
 
-	mutex_unlock(page_reporting_mutex);
+	mutex_unlock(&page_reporting_mutex);
 }
 EXPORT_SYMBOL_GPL(page_reporting_shutdown);
 
@@ -275,7 +275,7 @@ int page_reporting_startup(struct page_reporting_dev_info *phdev)
 	struct zone *zone;
 	int err = 0;
 
-	mutex_lock(page_reporting_mutex);
+	mutex_lock(&page_reporting_mutex);
 
 	/* nothing to do if already in use */
 	if (rcu_access_pointer(ph_dev_info)) {
@@ -305,7 +305,7 @@ int page_reporting_startup(struct page_reporting_dev_info *phdev)
 	/* enable page reporting notification */
 	static_key_slow_inc(&page_reporting_notify_enabled);
 err_out:
-	mutex_unlock(page_reporting_mutex);
+	mutex_unlock(&page_reporting_mutex);
 
 	return err;
 }