virtio: balloon: leak / fill balloon across S4 (4eb05d56) · Commits · 戴 / test

commit added support for S4 to the balloon driver. The freeze function did nothing to free the pages, since reclaiming the pages from the host to immediately give them back (if S4 was successful) seemed wasteful. Also, if S4 wasn't successful, the guest would have to re-fill the balloon. On restore, the pages were supposed to be marked freed and the free page counters were incremented to reflect the balloon was totally deflated. However, this wasn't done right. The pages that were earlier taken away from the guest during a balloon inflation operation were just shown as used pages after a successful restore from S4. Just a fancy way of leaking lots of memory. Instead of trying that, just leak the balloon on freeze and fill it on restore/thaw paths. This works properly now. The optimisation to not leak can be added later on after a bit of refactoring of the code. Signed-off-by:

Amit Shah <amit.shah@redhat.com> Signed-off-by:

Rusty Russell <rusty@rustcorp.com.au>

drivers/virtio/virtio_balloon.c

+22 −11

Original line number	Diff line number	Diff line
		@@ -367,29 +367,45 @@ static void __devexit virtballoon_remove(struct virtio_device *vdev)
		#ifdef CONFIG_PM
		static int virtballoon_freeze(struct virtio_device *vdev)
		{
		struct virtio_balloon *vb = vdev->priv;

		/*
		* The kthread is already frozen by the PM core before this
		* function is called.
		*/

		while (vb->num_pages)
		leak_balloon(vb, vb->num_pages);
		update_balloon_size(vb);

		/* Ensure we don't get any more requests from the host */
		vdev->config->reset(vdev);
		vdev->config->del_vqs(vdev);
		return 0;
		}

		static int restore_common(struct virtio_device *vdev)
		{
		struct virtio_balloon *vb = vdev->priv;
		int ret;

		ret = init_vqs(vdev->priv);
		if (ret)
		return ret;

		fill_balloon(vb, towards_target(vb));
		update_balloon_size(vb);
		return 0;
		}

		static int virtballoon_thaw(struct virtio_device *vdev)
		{
		return init_vqs(vdev->priv);
		return restore_common(vdev);
		}

		static int virtballoon_restore(struct virtio_device *vdev)
		{
		struct virtio_balloon *vb = vdev->priv;
		struct page page, page2;

		/* We're starting from a clean slate */
		vb->num_pages = 0;

		/*
		* If a request wasn't complete at the time of freezing, this
		@@ -397,12 +413,7 @@ static int virtballoon_restore(struct virtio_device *vdev)
		*/
		vb->need_stats_update = 0;

		/* We don't have these pages in the balloon anymore! */
		list_for_each_entry_safe(page, page2, &vb->pages, lru) {
		list_del(&page->lru);
		totalram_pages++;
		}
		return init_vqs(vdev->priv);
		return restore_common(vdev);
		}
		#endif

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