kvm: add oom notifier for virtio balloon

@@ -2,6 +2,7 @@
  * Tosatti's implementations.
  *
  *  Copyright 2008 Rusty Russell IBM Corporation
+ *  oom notify - Dave Young <[email protected]>
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by

@@ -25,6 +26,14 @@
 #include <linux/freezer.h>
 #include <linux/delay.h>
 #include <linux/slab.h>
+#include <linux/notifier.h>
+#include <linux/param.h>
+#include <linux/timer.h>
+#include <linux/jiffies.h>
+#include <linux/oom.h>
+
+#define BALLOON_OOM_DELAY_MINUTES	5
+#define BALLOON_OOM_PAGES		256
 
 struct virtio_balloon
 {

@@ -54,6 +63,10 @@ struct virtio_balloon
 	/* Memory statistics */
 	int need_stats_update;
 	struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
+
+	struct mutex mutex;
+	struct timer_list timer;
+	struct notifier_block oom_nb;
 };
 
 static struct virtio_device_id id_table[] = {

@@ -97,34 +110,37 @@ static void tell_host(struct virtio_ball
 	wait_for_completion(&vb->acked);
 }
 
+static void balloon_oom_timeout(unsigned long arg)
+{
+	struct virtio_balloon *v = (struct virtio_balloon *)arg;
+
+	wake_up(&v->config_change);
+}
+
 static void fill_balloon(struct virtio_balloon *vb, size_t num)
 {
 	/* We can only do one array worth at a time. */
 	num = min(num, ARRAY_SIZE(vb->pfns));
 
 	for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
-		struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY |
+		struct page *page;
+
+		if (unlikely(timer_pending(&vb->timer)))
+			break;
+
+		page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY |
 					__GFP_NOMEMALLOC | __GFP_NOWARN);
-		if (!page) {
-			if (printk_ratelimit())
-				dev_printk(KERN_INFO, &vb->vdev->dev,
-					   "Out of puff! Can't get %zu pages\n",
-					   num);
-			/* Sleep for at least 1/5 of a second before retry. */
-			msleep(200);
+		if (!page)
 			break;
-		}
+
 		vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
 		totalram_pages--;
 		vb->num_pages++;
 		list_add(&page->lru, &vb->pages);
 	}
 
-	/* Didn't get any?  Oh well. */
-	if (vb->num_pfns == 0)
-		return;
-
-	tell_host(vb, vb->inflate_vq);
+	if (vb->num_pfns)
+		tell_host(vb, vb->inflate_vq);
 }
 
 static void release_pages_by_pfn(const u32 pfns[], unsigned int num)

@@ -235,22 +251,53 @@ static void virtballoon_changed(struct v
 
 static inline s64 towards_target(struct virtio_balloon *vb)
 {
-	u32 v;
+	u32 v, ret;
 	vb->vdev->config->get(vb->vdev,
 			      offsetof(struct virtio_balloon_config, num_pages),
 			      &v, sizeof(v));
-	return (s64)v - vb->num_pages;
+	ret = (s64)v - vb->num_pages;
+
+	if (ret > 0 && (unlikely(timer_pending(&vb->timer)))) {
+		printk(KERN_INFO "balloon will delay inflate due to oom ...\n");
+		return 0;
+	}
+
+	return ret;
 }
 
 static void update_balloon_size(struct virtio_balloon *vb)
 {
-	__le32 actual = cpu_to_le32(vb->num_pages);
+	__le32 actual;
 
+	actual = cpu_to_le32(vb->num_pages);
 	vb->vdev->config->set(vb->vdev,
 			      offsetof(struct virtio_balloon_config, actual),
 			      &actual, sizeof(actual));
 }
 
+static int balloon_oom_notify(struct notifier_block *self,
+				unsigned long dummy, void *parm)
+{
+	struct virtio_balloon *vb;
+	unsigned long *freed = (unsigned long *)parm;
+	unsigned int nr;
+
+	vb = container_of(self, struct virtio_balloon, oom_nb);
+
+	mutex_lock(&vb->mutex);
+	nr = min_t(unsigned int, vb->num_pages, BALLOON_OOM_PAGES);
+	if (nr) {
+		printk(KERN_INFO "balloon oom notifier leak %d pages\n", nr);
+		leak_balloon(vb, nr);
+		update_balloon_size(vb);
+	}
+	*freed = nr;
+	mutex_unlock(&vb->mutex);
+	mod_timer(&vb->timer, jiffies + BALLOON_OOM_DELAY_MINUTES * 60 * HZ);
+
+	return NOTIFY_OK;
+}
+
 static int balloon(void *_vballoon)
 {
 	struct virtio_balloon *vb = _vballoon;

@@ -267,11 +314,14 @@ static int balloon(void *_vballoon)
 					 || freezing(current));
 		if (vb->need_stats_update)
 			stats_handle_request(vb);
+
+		mutex_lock(&vb->mutex);
 		if (diff > 0)
 			fill_balloon(vb, diff);
 		else if (diff < 0)
 			leak_balloon(vb, -diff);
 		update_balloon_size(vb);
+		mutex_unlock(&vb->mutex);
 	}
 	return 0;
 }

@@ -325,6 +375,13 @@ static int virtballoon_probe(struct virt
 
 	vb->tell_host_first
 		= virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
+	vb->oom_nb.notifier_call = balloon_oom_notify;
+
+	mutex_init(&vb->mutex);
+	err = register_oom_notifier(&vb->oom_nb);
+	if (err < 0)
+		goto out_del_vqs;
+	setup_timer(&vb->timer, balloon_oom_timeout, (unsigned long)vb);
 
 	return 0;
 

@@ -340,6 +397,7 @@ static void __devexit virtballoon_remove
 {
 	struct virtio_balloon *vb = vdev->priv;
 
+	unregister_oom_notifier(&vb->oom_nb);
 	kthread_stop(vb->thread);
 
 	/* There might be pages left in the balloon: free them. */