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path: root/drivers/virtio/virtio_balloon.c
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Diffstat (limited to 'drivers/virtio/virtio_balloon.c')
-rw-r--r--drivers/virtio/virtio_balloon.c52
1 files changed, 52 insertions, 0 deletions
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index ff71fdcf3345..50c5f42d7a9f 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -28,6 +28,7 @@
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/balloon_compaction.h>
+#include <linux/oom.h>
/*
* Balloon device works in 4K page units. So each page is pointed to by
@@ -36,6 +37,12 @@
*/
#define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
#define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
+#define OOM_VBALLOON_DEFAULT_PAGES 256
+#define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
+
+static int oom_pages = OOM_VBALLOON_DEFAULT_PAGES;
+module_param(oom_pages, int, S_IRUSR | S_IWUSR);
+MODULE_PARM_DESC(oom_pages, "pages to free on OOM");
struct virtio_balloon
{
@@ -71,6 +78,9 @@ struct virtio_balloon
/* Memory statistics */
int need_stats_update;
struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
+
+ /* To register callback in oom notifier call chain */
+ struct notifier_block nb;
};
static struct virtio_device_id id_table[] = {
@@ -290,6 +300,38 @@ static void update_balloon_size(struct virtio_balloon *vb)
&actual);
}
+/*
+ * virtballoon_oom_notify - release pages when system is under severe
+ * memory pressure (called from out_of_memory())
+ * @self : notifier block struct
+ * @dummy: not used
+ * @parm : returned - number of freed pages
+ *
+ * The balancing of memory by use of the virtio balloon should not cause
+ * the termination of processes while there are pages in the balloon.
+ * If virtio balloon manages to release some memory, it will make the
+ * system return and retry the allocation that forced the OOM killer
+ * to run.
+ */
+static int virtballoon_oom_notify(struct notifier_block *self,
+ unsigned long dummy, void *parm)
+{
+ struct virtio_balloon *vb;
+ unsigned long *freed;
+ unsigned num_freed_pages;
+
+ vb = container_of(self, struct virtio_balloon, nb);
+ if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
+ return NOTIFY_OK;
+
+ freed = parm;
+ num_freed_pages = leak_balloon(vb, oom_pages);
+ update_balloon_size(vb);
+ *freed += num_freed_pages;
+
+ return NOTIFY_OK;
+}
+
static int balloon(void *_vballoon)
{
struct virtio_balloon *vb = _vballoon;
@@ -446,6 +488,12 @@ static int virtballoon_probe(struct virtio_device *vdev)
if (err)
goto out_free_vb;
+ vb->nb.notifier_call = virtballoon_oom_notify;
+ vb->nb.priority = VIRTBALLOON_OOM_NOTIFY_PRIORITY;
+ err = register_oom_notifier(&vb->nb);
+ if (err < 0)
+ goto out_oom_notify;
+
vb->thread = kthread_run(balloon, vb, "vballoon");
if (IS_ERR(vb->thread)) {
err = PTR_ERR(vb->thread);
@@ -455,6 +503,8 @@ static int virtballoon_probe(struct virtio_device *vdev)
return 0;
out_del_vqs:
+ unregister_oom_notifier(&vb->nb);
+out_oom_notify:
vdev->config->del_vqs(vdev);
out_free_vb:
kfree(vb);
@@ -479,6 +529,7 @@ static void virtballoon_remove(struct virtio_device *vdev)
{
struct virtio_balloon *vb = vdev->priv;
+ unregister_oom_notifier(&vb->nb);
kthread_stop(vb->thread);
remove_common(vb);
kfree(vb);
@@ -518,6 +569,7 @@ static int virtballoon_restore(struct virtio_device *vdev)
static unsigned int features[] = {
VIRTIO_BALLOON_F_MUST_TELL_HOST,
VIRTIO_BALLOON_F_STATS_VQ,
+ VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
};
static struct virtio_driver virtio_balloon_driver = {