drivers/virtio/virtio_balloon.c - kernel/msm - Gitiles

 /* Virtio balloon implementation, inspired by Dor Loar and Marcelo
  * Tosatti's implementations.
  *
  *  Copyright 2008 Rusty Russell IBM Corporation
  *
  *  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
  *  the Free Software Foundation; either version 2 of the License, or
  *  (at your option) any later version.
  *
  *  This program is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  *  GNU General Public License for more details.
  *
  *  You should have received a copy of the GNU General Public License
  *  along with this program; if not, write to the Free Software
  *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  */
 //#define DEBUG
 #include <linux/virtio.h>
 #include <linux/virtio_balloon.h>
 #include <linux/swap.h>
 #include <linux/kthread.h>
 #include <linux/freezer.h>

 struct virtio_balloon
 {
 	struct virtio_device *vdev;
 	struct virtqueue *inflate_vq, *deflate_vq;

 	/* Where the ballooning thread waits for config to change. */
 	wait_queue_head_t config_change;

 	/* The thread servicing the balloon. */
 	struct task_struct *thread;

 	/* Waiting for host to ack the pages we released. */
 	struct completion acked;

 	/* Do we have to tell Host *before* we reuse pages? */
 	bool tell_host_first;

 	/* The pages we've told the Host we're not using. */
 	unsigned int num_pages;
 	struct list_head pages;

 	/* The array of pfns we tell the Host about. */
 	unsigned int num_pfns;
 	u32 pfns[256];
 };

 static struct virtio_device_id id_table[] = {
 	{ VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
 	{ 0 },
 };

 static void balloon_ack(struct virtqueue *vq)
 {
 	struct virtio_balloon *vb;
 	unsigned int len;

 	vb = vq->vq_ops->get_buf(vq, &len);
 	if (vb)
 		complete(&vb->acked);
 }

 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
 {
 	struct scatterlist sg;

 	sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);

 	init_completion(&vb->acked);

 	/* We should always be able to add one buffer to an empty queue. */
 	if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) != 0)
 		BUG();
 	vq->vq_ops->kick(vq);

 	/* When host has read buffer, this completes via balloon_ack */
 	wait_for_completion(&vb->acked);
 }

 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);
 		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);
 			break;
 		}
 		vb->pfns[vb->num_pfns] = page_to_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);
 }

 static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
 {
 	unsigned int i;

 	for (i = 0; i < num; i++) {
 		__free_page(pfn_to_page(pfns[i]));
 		totalram_pages++;
 	}
 }

 static void leak_balloon(struct virtio_balloon *vb, size_t num)
 {
 	struct page *page;

 	/* 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++) {
 		page = list_first_entry(&vb->pages, struct page, lru);
 		list_del(&page->lru);
 		vb->pfns[vb->num_pfns] = page_to_pfn(page);
 		vb->num_pages--;
 	}

 	if (vb->tell_host_first) {
 		tell_host(vb, vb->deflate_vq);
 		release_pages_by_pfn(vb->pfns, vb->num_pfns);
 	} else {
 		release_pages_by_pfn(vb->pfns, vb->num_pfns);
 		tell_host(vb, vb->deflate_vq);
 	}
 }

 static void virtballoon_changed(struct virtio_device *vdev)
 {
 	struct virtio_balloon *vb = vdev->priv;

 	wake_up(&vb->config_change);
 }

 static inline int towards_target(struct virtio_balloon *vb)
 {
 	u32 v;
 	__virtio_config_val(vb->vdev,
 			    offsetof(struct virtio_balloon_config, num_pages),
 			    &v);
 	return v - vb->num_pages;
 }

 static void update_balloon_size(struct virtio_balloon *vb)
 {
 	__le32 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(void *_vballoon)
 {
 	struct virtio_balloon *vb = _vballoon;

 	set_freezable();
 	while (!kthread_should_stop()) {
 		int diff;

 		try_to_freeze();
 		wait_event_interruptible(vb->config_change,
 					 (diff = towards_target(vb)) != 0
 					 || kthread_should_stop());
 		if (diff > 0)
 			fill_balloon(vb, diff);
 		else if (diff < 0)
 			leak_balloon(vb, -diff);
 		update_balloon_size(vb);
 	}
 	return 0;
 }

 static int virtballoon_probe(struct virtio_device *vdev)
 {
 	struct virtio_balloon *vb;
 	int err;

 	vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
 	if (!vb) {
 		err = -ENOMEM;
 		goto out;
 	}

 	INIT_LIST_HEAD(&vb->pages);
 	vb->num_pages = 0;
 	init_waitqueue_head(&vb->config_change);
 	vb->vdev = vdev;

 	/* We expect two virtqueues. */
 	vb->inflate_vq = vdev->config->find_vq(vdev, 0, balloon_ack);
 	if (IS_ERR(vb->inflate_vq)) {
 		err = PTR_ERR(vb->inflate_vq);
 		goto out_free_vb;
 	}

 	vb->deflate_vq = vdev->config->find_vq(vdev, 1, balloon_ack);
 	if (IS_ERR(vb->deflate_vq)) {
 		err = PTR_ERR(vb->deflate_vq);
 		goto out_del_inflate_vq;
 	}

 	vb->thread = kthread_run(balloon, vb, "vballoon");
 	if (IS_ERR(vb->thread)) {
 		err = PTR_ERR(vb->thread);
 		goto out_del_deflate_vq;
 	}

 	vb->tell_host_first
 		= vdev->config->feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);

 	return 0;

 out_del_deflate_vq:
 	vdev->config->del_vq(vb->deflate_vq);
 out_del_inflate_vq:
 	vdev->config->del_vq(vb->inflate_vq);
 out_free_vb:
 	kfree(vb);
 out:
 	return err;
 }

 static void virtballoon_remove(struct virtio_device *vdev)
 {
 	struct virtio_balloon *vb = vdev->priv;

 	kthread_stop(vb->thread);

 	/* There might be pages left in the balloon: free them. */
 	while (vb->num_pages)
 		leak_balloon(vb, vb->num_pages);

 	/* Now we reset the device so we can clean up the queues. */
 	vdev->config->reset(vdev);

 	vdev->config->del_vq(vb->deflate_vq);
 	vdev->config->del_vq(vb->inflate_vq);
 	kfree(vb);
 }

 static struct virtio_driver virtio_balloon = {
 	.driver.name =	KBUILD_MODNAME,
 	.driver.owner =	THIS_MODULE,
 	.id_table =	id_table,
 	.probe =	virtballoon_probe,
 	.remove =	__devexit_p(virtballoon_remove),
 	.config_changed = virtballoon_changed,
 };

 static int __init init(void)
 {
 	return register_virtio_driver(&virtio_balloon);
 }

 static void __exit fini(void)
 {
 	unregister_virtio_driver(&virtio_balloon);
 }
 module_init(init);
 module_exit(fini);

 MODULE_DEVICE_TABLE(virtio, id_table);
 MODULE_DESCRIPTION("Virtio balloon driver");
 MODULE_LICENSE("GPL");
	/* Virtio balloon implementation, inspired by Dor Loar and Marcelo
	* Tosatti's implementations.
	*
	* Copyright 2008 Rusty Russell IBM Corporation
	*
	* 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
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
	*/
	//#define DEBUG
	#include <linux/virtio.h>
	#include <linux/virtio_balloon.h>
	#include <linux/swap.h>
	#include <linux/kthread.h>
	#include <linux/freezer.h>

	struct virtio_balloon
	{
	struct virtio_device *vdev;
	struct virtqueue inflate_vq, deflate_vq;

	/* Where the ballooning thread waits for config to change. */
	wait_queue_head_t config_change;

	/* The thread servicing the balloon. */
	struct task_struct *thread;

	/* Waiting for host to ack the pages we released. */
	struct completion acked;

	/* Do we have to tell Host before we reuse pages? */
	bool tell_host_first;

	/* The pages we've told the Host we're not using. */
	unsigned int num_pages;
	struct list_head pages;

	/* The array of pfns we tell the Host about. */
	unsigned int num_pfns;
	u32 pfns[256];
	};

	static struct virtio_device_id id_table[] = {
	{ VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
	{ 0 },
	};

	static void balloon_ack(struct virtqueue *vq)
	{
	struct virtio_balloon *vb;
	unsigned int len;

	vb = vq->vq_ops->get_buf(vq, &len);
	if (vb)
	complete(&vb->acked);
	}

	static void tell_host(struct virtio_balloon vb, struct virtqueue vq)
	{
	struct scatterlist sg;

	sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);

	init_completion(&vb->acked);

	/* We should always be able to add one buffer to an empty queue. */
	if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) != 0)
	BUG();
	vq->vq_ops->kick(vq);

	/* When host has read buffer, this completes via balloon_ack */
	wait_for_completion(&vb->acked);
	}

	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);
	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);
	break;
	}
	vb->pfns[vb->num_pfns] = page_to_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);
	}

	static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
	{
	unsigned int i;

	for (i = 0; i < num; i++) {
	__free_page(pfn_to_page(pfns[i]));
	totalram_pages++;
	}
	}

	static void leak_balloon(struct virtio_balloon *vb, size_t num)
	{
	struct page *page;

	/* 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++) {
	page = list_first_entry(&vb->pages, struct page, lru);
	list_del(&page->lru);
	vb->pfns[vb->num_pfns] = page_to_pfn(page);
	vb->num_pages--;
	}

	if (vb->tell_host_first) {
	tell_host(vb, vb->deflate_vq);
	release_pages_by_pfn(vb->pfns, vb->num_pfns);
	} else {
	release_pages_by_pfn(vb->pfns, vb->num_pfns);
	tell_host(vb, vb->deflate_vq);
	}
	}

	static void virtballoon_changed(struct virtio_device *vdev)
	{
	struct virtio_balloon *vb = vdev->priv;

	wake_up(&vb->config_change);
	}

	static inline int towards_target(struct virtio_balloon *vb)
	{
	u32 v;
	__virtio_config_val(vb->vdev,
	offsetof(struct virtio_balloon_config, num_pages),
	&v);
	return v - vb->num_pages;
	}

	static void update_balloon_size(struct virtio_balloon *vb)
	{
	__le32 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(void *_vballoon)
	{
	struct virtio_balloon *vb = _vballoon;

	set_freezable();
	while (!kthread_should_stop()) {
	int diff;

	try_to_freeze();
	wait_event_interruptible(vb->config_change,
	(diff = towards_target(vb)) != 0
	\|\| kthread_should_stop());
	if (diff > 0)
	fill_balloon(vb, diff);
	else if (diff < 0)
	leak_balloon(vb, -diff);
	update_balloon_size(vb);
	}
	return 0;
	}

	static int virtballoon_probe(struct virtio_device *vdev)
	{
	struct virtio_balloon *vb;
	int err;

	vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
	if (!vb) {
	err = -ENOMEM;
	goto out;
	}

	INIT_LIST_HEAD(&vb->pages);
	vb->num_pages = 0;
	init_waitqueue_head(&vb->config_change);
	vb->vdev = vdev;

	/* We expect two virtqueues. */
	vb->inflate_vq = vdev->config->find_vq(vdev, 0, balloon_ack);
	if (IS_ERR(vb->inflate_vq)) {
	err = PTR_ERR(vb->inflate_vq);
	goto out_free_vb;
	}

	vb->deflate_vq = vdev->config->find_vq(vdev, 1, balloon_ack);
	if (IS_ERR(vb->deflate_vq)) {
	err = PTR_ERR(vb->deflate_vq);
	goto out_del_inflate_vq;
	}

	vb->thread = kthread_run(balloon, vb, "vballoon");
	if (IS_ERR(vb->thread)) {
	err = PTR_ERR(vb->thread);
	goto out_del_deflate_vq;
	}

	vb->tell_host_first
	= vdev->config->feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);

	return 0;

	out_del_deflate_vq:
	vdev->config->del_vq(vb->deflate_vq);
	out_del_inflate_vq:
	vdev->config->del_vq(vb->inflate_vq);
	out_free_vb:
	kfree(vb);
	out:
	return err;
	}

	static void virtballoon_remove(struct virtio_device *vdev)
	{
	struct virtio_balloon *vb = vdev->priv;

	kthread_stop(vb->thread);

	/* There might be pages left in the balloon: free them. */
	while (vb->num_pages)
	leak_balloon(vb, vb->num_pages);

	/* Now we reset the device so we can clean up the queues. */
	vdev->config->reset(vdev);

	vdev->config->del_vq(vb->deflate_vq);
	vdev->config->del_vq(vb->inflate_vq);
	kfree(vb);
	}

	static struct virtio_driver virtio_balloon = {
	.driver.name = KBUILD_MODNAME,
	.driver.owner = THIS_MODULE,
	.id_table = id_table,
	.probe = virtballoon_probe,
	.remove = __devexit_p(virtballoon_remove),
	.config_changed = virtballoon_changed,
	};

	static int __init init(void)
	{
	return register_virtio_driver(&virtio_balloon);
	}

	static void __exit fini(void)
	{
	unregister_virtio_driver(&virtio_balloon);
	}
	module_init(init);
	module_exit(fini);

	MODULE_DEVICE_TABLE(virtio, id_table);
	MODULE_DESCRIPTION("Virtio balloon driver");
	MODULE_LICENSE("GPL");