text: /*
   * Virtio balloon implementation, inspired by Dor Laor 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
   */
  
  #include <linux/virtio.h>
  #include <linux/virtio_balloon.h>
  #include <linux/swap.h>
  #include <linux/workqueue.h>
  #include <linux/delay.h>
  #include <linux/slab.h>
  #include <linux/module.h>
  #include <linux/balloon_compaction.h>
  #include <linux/wait.h>
  #include <linux/mm.h>
  #include <linux/mount.h>
  #include <linux/magic.h>
  
  /*
   * Balloon device works in 4K page units.  So each page is pointed to by
   * multiple balloon pages.  All memory counters in this driver are in balloon
   * page units.
   */
  #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
  #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
  #define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
  
  #ifdef CONFIG_BALLOON_COMPACTION
  static struct vfsmount *balloon_mnt;
  #endif
  
  struct virtio_balloon {
  	struct virtio_device *vdev;
  	struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
  
  	/* The balloon servicing is delegated to a freezable workqueue. */
  	struct work_struct update_balloon_stats_work;
  	struct work_struct update_balloon_size_work;
  
  	/* Prevent updating balloon when it is being canceled. */
  	spinlock_t stop_update_lock;
  	bool stop_update;
  
  	/* Waiting for host to ack the pages we released. */
  	wait_queue_head_t acked;
  
  	/* Number of balloon pages we've told the Host we're not using. */
  	unsigned int num_pages;
  	/*
  	 * The pages we've told the Host we're not using are enqueued
  	 * at vb_dev_info->pages list.
  	 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
  	 * to num_pages above.
  	 */
  	struct balloon_dev_info vb_dev_info;
  
  	/* Synchronize access/update to this struct virtio_balloon elements */
  	struct mutex balloon_lock;
  
  	/* The array of pfns we tell the Host about. */
  	unsigned int num_pfns;
  	__virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
  
  	/* Memory statistics */
  	struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
  
  	/* To register a shrinker to shrink memory upon memory pressure */
  	struct shrinker shrinker;
  };
  
  static struct virtio_device_id id_table[] = {
  	{ VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
  	{ 0 },
  };
  
  static u32 page_to_balloon_pfn(struct page *page)
  {
  	unsigned long pfn = page_to_pfn(page);
  
  	BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
  	/* Convert pfn from Linux page size to balloon page size. */
  	return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
  }
  
  static void balloon_ack(struct virtqueue *vq)
  {
  	struct virtio_balloon *vb = vq->vdev->priv;
  
  	wake_up(&vb->acked);
  }
  
  static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
  {
  	struct scatterlist sg;
  	unsigned int len;
  
  	sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
  
  	/* We should always be able to add one buffer to an empty queue. */
  	virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
  	virtqueue_kick(vq);
  
  	/* When host has read buffer, this completes via balloon_ack */
  	wait_event(vb->acked, virtqueue_get_buf(vq, &len));
  
  }
  
  static void set_page_pfns(struct virtio_balloon *vb,
  			  __virtio32 pfns[], struct page *page)
  {
  	unsigned int i;
  
  	/*
  	 * Set balloon pfns pointing at this page.
  	 * Note that the first pfn points at start of the page.
  	 */
  	for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
  		pfns[i] = cpu_to_virtio32(vb->vdev,
  					  page_to_balloon_pfn(page) + i);
  }
  
  static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
  {
  	unsigned num_allocated_pages;
  	unsigned num_pfns;
  	struct page *page;
  	LIST_HEAD(pages);
  
  	/* We can only do one array worth at a time. */
  	num = min(num, ARRAY_SIZE(vb->pfns));
  
  	for (num_pfns = 0; num_pfns < num;
  	     num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
  		struct page *page = balloon_page_alloc();
  
  		if (!page) {
  			dev_info_ratelimited(&vb->vdev->dev,
  					     "Out of puff! Can't get %u pages\n",
  					     VIRTIO_BALLOON_PAGES_PER_PAGE);
  			/* Sleep for at least 1/5 of a second before retry. */
  			msleep(200);
  			break;
  		}
  
  		balloon_page_push(&pages, page);
  	}
  
  	mutex_lock(&vb->balloon_lock);
  
  	vb->num_pfns = 0;
  
  	while ((page = balloon_page_pop(&pages))) {
  		balloon_page_enqueue(&vb->vb_dev_info, page);
  
  		set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
  		vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
  		if (!virtio_has_feature(vb->vdev,
  					VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
  			adjust_managed_page_count(page, -1);
  		vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE;
  	}
  
  	num_allocated_pages = vb->num_pfns;
  	/* Did we get any? */
  	if (vb->num_pfns != 0)
  		tell_host(vb, vb->inflate_vq);
  	mutex_unlock(&vb->balloon_lock);
  
  	return num_allocated_pages;
  }
  
  static void release_pages_balloon(struct virtio_balloon *vb,
  				 struct list_head *pages)
  {
  	struct page *page, *next;
  
  	list_for_each_entry_safe(page, next, pages, lru) {
  		if (!virtio_has_feature(vb->vdev,
  					VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
  			adjust_managed_page_count(page, 1);
  		list_del(&page->lru);
  		put_page(page); /* balloon reference */
  	}
  }
  
  static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
  {
  	unsigned num_freed_pages;
  	struct page *page;
  	struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
  	LIST_HEAD(pages);
  
  	/* We can only do one array worth at a time. */
  	num = min(num, ARRAY_SIZE(vb->pfns));
  
  	mutex_lock(&vb->balloon_lock);
  	/* We can't release more pages than taken */
  	num = min(num, (size_t)vb->num_pages);
  	for (vb->num_pfns = 0; vb->num_pfns < num;
  	     vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
  		page = balloon_page_dequeue(vb_dev_info);
  		if (!page)
  			break;
  		set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
  		list_add(&page->lru, &pages);
  		vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
  	}
  
  	num_freed_pages = vb->num_pfns;
  	/*
  	 * Note that if
  	 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
  	 * is true, we *have* to do it in this order
  	 */
  	if (vb->num_pfns != 0)
  		tell_host(vb, vb->deflate_vq);
  	release_pages_balloon(vb, &pages);
  	mutex_unlock(&vb->balloon_lock);
  	return num_freed_pages;
  }
  
  static inline void update_stat(struct virtio_balloon *vb, int idx,
  			       u16 tag, u64 val)
  {
  	BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
  	vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
  	vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
  }
  
  #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
  
  static unsigned int update_balloon_stats(struct virtio_balloon *vb)
  {
  	unsigned long events[NR_VM_EVENT_ITEMS];
  	struct sysinfo i;
  	unsigned int idx = 0;
  	long available;
  	unsigned long caches;
  
  	all_vm_events(events);
  	si_meminfo(&i);
  
  	available = si_mem_available();
  	caches = global_node_page_state(NR_FILE_PAGES);
  
  #ifdef CONFIG_VM_EVENT_COUNTERS
  	update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
  				pages_to_bytes(events[PSWPIN]));
  	update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
  				pages_to_bytes(events[PSWPOUT]));
  	update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
  	update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
  #ifdef CONFIG_HUGETLB_PAGE
  	update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC,
  		    events[HTLB_BUDDY_PGALLOC]);
  	update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL,
  		    events[HTLB_BUDDY_PGALLOC_FAIL]);
  #endif
  #endif
  	update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
  				pages_to_bytes(i.freeram));
  	update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
  				pages_to_bytes(i.totalram));
  	update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
  				pages_to_bytes(available));
  	update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES,
  				pages_to_bytes(caches));
  
  	return idx;
  }
  
  /*
   * While most virtqueues communicate guest-initiated requests to the hypervisor,
   * the stats queue operates in reverse.  The driver initializes the virtqueue
   * with a single buffer.  From that point forward, all conversations consist of
   * a hypervisor request (a call to this function) which directs us to refill
   * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
   * we delegate the job to a freezable workqueue that will do the actual work via
   * stats_handle_request().
   */
  static void stats_request(struct virtqueue *vq)
  {
  	struct virtio_balloon *vb = vq->vdev->priv;
  
  	spin_lock(&vb->stop_update_lock);
  	if (!vb->stop_update)
  		queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
  	spin_unlock(&vb->stop_update_lock);
  }
  
  static void stats_handle_request(struct virtio_balloon *vb)
  {
  	struct virtqueue *vq;
  	struct scatterlist sg;
  	unsigned int len, num_stats;
  
  	num_stats = update_balloon_stats(vb);
  
  	vq = vb->stats_vq;
  	if (!virtqueue_get_buf(vq, &len))
  		return;
  	sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
  	virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
  	virtqueue_kick(vq);
  }
  
  static void virtballoon_changed(struct virtio_device *vdev)
  {
  	struct virtio_balloon *vb = vdev->priv;
  	unsigned long flags;
  
  	spin_lock_irqsave(&vb->stop_update_lock, flags);
  	if (!vb->stop_update)
  		queue_work(system_freezable_wq, &vb->update_balloon_size_work);
  	spin_unlock_irqrestore(&vb->stop_update_lock, flags);
  }
  
  static inline s64 towards_target(struct virtio_balloon *vb)
  {
  	s64 target;
  	u32 num_pages;
  
  	virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
  		     &num_pages);
  
  	/* Legacy balloon config space is LE, unlike all other devices. */
  	if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
  		num_pages = le32_to_cpu((__force __le32)num_pages);
  
  	target = num_pages;
  	return target - vb->num_pages;
  }
  
  static void update_balloon_size(struct virtio_balloon *vb)
  {
  	u32 actual = vb->num_pages;
  
  	/* Legacy balloon config space is LE, unlike all other devices. */
  	if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
  		actual = (__force u32)cpu_to_le32(actual);
  
  	virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
  		      &actual);
  }
  
  static void update_balloon_stats_func(struct work_struct *work)
  {
  	struct virtio_balloon *vb;
  
  	vb = container_of(work, struct virtio_balloon,
  			  update_balloon_stats_work);
  	stats_handle_request(vb);
  }
  
  static void update_balloon_size_func(struct work_struct *work)
  {
  	struct virtio_balloon *vb;
  	s64 diff;
  
  	vb = container_of(work, struct virtio_balloon,
  			  update_balloon_size_work);
  	diff = towards_target(vb);
  
  	if (diff > 0)
  		diff -= fill_balloon(vb, diff);
  	else if (diff < 0)
  		diff += leak_balloon(vb, -diff);
  	update_balloon_size(vb);
  
  	if (diff)
  		queue_work(system_freezable_wq, work);
  }
  
  static int init_vqs(struct virtio_balloon *vb)
  {
  	struct virtqueue *vqs[3];
  	vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
  	static const char * const names[] = { "inflate", "deflate", "stats" };
  	int err, nvqs;
  
  	/*
  	 * We expect two virtqueues: inflate and deflate, and
  	 * optionally stat.
  	 */
  	nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
  	err = virtio_find_vqs(vb->vdev, nvqs, vqs, callbacks, names, NULL);
  	if (err)
  		return err;
  
  	vb->inflate_vq = vqs[0];
  	vb->deflate_vq = vqs[1];
  	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
  		struct scatterlist sg;
  		unsigned int num_stats;
  		vb->stats_vq = vqs[2];
  
  		/*
  		 * Prime this virtqueue with one buffer so the hypervisor can
  		 * use it to signal us later (it can't be broken yet!).
  		 */
  		num_stats = update_balloon_stats(vb);
  
  		sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
  		err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb,
  					   GFP_KERNEL);
  		if (err) {
  			dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
  				 __func__);
  			return err;
  		}
  		virtqueue_kick(vb->stats_vq);
  	}
  	return 0;
  }
  
  #ifdef CONFIG_BALLOON_COMPACTION
  /*
   * virtballoon_migratepage - perform the balloon page migration on behalf of
   *			     a compation thread.     (called under page lock)
   * @vb_dev_info: the balloon device
   * @newpage: page that will replace the isolated page after migration finishes.
   * @page   : the isolated (old) page that is about to be migrated to newpage.
   * @mode   : compaction mode -- not used for balloon page migration.
   *
   * After a ballooned page gets isolated by compaction procedures, this is the
   * function that performs the page migration on behalf of a compaction thread
   * The page migration for virtio balloon is done in a simple swap fashion which
   * follows these two macro steps:
   *  1) insert newpage into vb->pages list and update the host about it;
   *  2) update the host about the old page removed from vb->pages list;
   *
   * This function preforms the balloon page migration task.
   * Called through balloon_mapping->a_ops->migratepage
   */
  static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
  		struct page *newpage, struct page *page, enum migrate_mode mode)
  {
  	struct virtio_balloon *vb = container_of(vb_dev_info,
  			struct virtio_balloon, vb_dev_info);
  	unsigned long flags;
  
  	/*
  	 * In order to avoid lock contention while migrating pages concurrently
  	 * to leak_balloon() or fill_balloon() we just give up the balloon_lock
  	 * this turn, as it is easier to retry the page migration later.
  	 * This also prevents fill_balloon() getting stuck into a mutex
  	 * recursion in the case it ends up triggering memory compaction
  	 * while it is attempting to inflate the ballon.
  	 */
  	if (!mutex_trylock(&vb->balloon_lock))
  		return -EAGAIN;
  
  	get_page(newpage); /* balloon reference */
  
  	/* balloon's page migration 1st step  -- inflate "newpage" */
  	spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
  	balloon_page_insert(vb_dev_info, newpage);
  	vb_dev_info->isolated_pages--;
  	__count_vm_event(BALLOON_MIGRATE);
  	spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
  	vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
  	set_page_pfns(vb, vb->pfns, newpage);
  	tell_host(vb, vb->inflate_vq);
  
  	/* balloon's page migration 2nd step -- deflate "page" */
  	spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
  	balloon_page_delete(page);
  	spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
  	vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
  	set_page_pfns(vb, vb->pfns, page);
  	tell_host(vb, vb->deflate_vq);
  
  	mutex_unlock(&vb->balloon_lock);
  
  	put_page(page); /* balloon reference */
  
  	return MIGRATEPAGE_SUCCESS;
  }
  
  static struct dentry *balloon_mount(struct file_system_type *fs_type,
  		int flags, const char *dev_name, void *data)
  {
  	static const struct dentry_operations ops = {
  		.d_dname = simple_dname,
  	};
  
  	return mount_pseudo(fs_type, "balloon-kvm:", NULL, &ops,
  				BALLOON_KVM_MAGIC);
  }
  
  static struct file_system_type balloon_fs = {
  	.name           = "balloon-kvm",
  	.mount          = balloon_mount,
  	.kill_sb        = kill_anon_super,
  };
  
  #endif /* CONFIG_BALLOON_COMPACTION */
  
  static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
  						  struct shrink_control *sc)
  {
  	unsigned long pages_to_free, pages_freed = 0;
  	struct virtio_balloon *vb = container_of(shrinker,
  					struct virtio_balloon, shrinker);
  
  	pages_to_free = sc->nr_to_scan * VIRTIO_BALLOON_PAGES_PER_PAGE;
  
  	/*
  	 * One invocation of leak_balloon can deflate at most
  	 * VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it
  	 * multiple times to deflate pages till reaching pages_to_free.
  	 */
  	while (vb->num_pages && pages_to_free) {
  		pages_to_free -= pages_freed;
  		pages_freed += leak_balloon(vb, pages_to_free);
  	}
  	update_balloon_size(vb);
  
  	return pages_freed / VIRTIO_BALLOON_PAGES_PER_PAGE;
  }
  
  static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
  						   struct shrink_control *sc)
  {
  	struct virtio_balloon *vb = container_of(shrinker,
  					struct virtio_balloon, shrinker);
  
  	return vb->num_pages / VIRTIO_BALLOON_PAGES_PER_PAGE;
  }
  
  static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
  {
  	unregister_shrinker(&vb->shrinker);
  }
  
  static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
  {
  	vb->shrinker.scan_objects = virtio_balloon_shrinker_scan;
  	vb->shrinker.count_objects = virtio_balloon_shrinker_count;
  	vb->shrinker.seeks = DEFAULT_SEEKS;
  
  	return register_shrinker(&vb->shrinker);
  }
  
  static int virtballoon_probe(struct virtio_device *vdev)
  {
  	struct virtio_balloon *vb;
  	int err;
  
  	if (!vdev->config->get) {
  		dev_err(&vdev->dev, "%s failure: config access disabled\n",
  			__func__);
  		return -EINVAL;
  	}
  
  	vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL);
  	if (!vb) {
  		err = -ENOMEM;
  		goto out;
  	}
  
  	INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
  	INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
  	spin_lock_init(&vb->stop_update_lock);
  	mutex_init(&vb->balloon_lock);
  	init_waitqueue_head(&vb->acked);
  	vb->vdev = vdev;
  
  	balloon_devinfo_init(&vb->vb_dev_info);
  
  	err = init_vqs(vb);
  	if (err)
  		goto out_free_vb;
  
  #ifdef CONFIG_BALLOON_COMPACTION
  	balloon_mnt = kern_mount(&balloon_fs);
  	if (IS_ERR(balloon_mnt)) {
  		err = PTR_ERR(balloon_mnt);
  		goto out_del_vqs;
  	}
  
  	vb->vb_dev_info.migratepage = virtballoon_migratepage;
  	vb->vb_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb);
  	if (IS_ERR(vb->vb_dev_info.inode)) {
  		err = PTR_ERR(vb->vb_dev_info.inode);
  		kern_unmount(balloon_mnt);
  		goto out_del_vqs;
  	}
  	vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops;
  #endif
  	/*
  	 * We continue to use VIRTIO_BALLOON_F_DEFLATE_ON_OOM to decide if a
  	 * shrinker needs to be registered to relieve memory pressure.
  	 */
  	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
  		err = virtio_balloon_register_shrinker(vb);
  		if (err)
  			goto out_del_vqs;
  	}
  	virtio_device_ready(vdev);
  
  	if (towards_target(vb))
  		virtballoon_changed(vdev);
  	return 0;
  
  out_del_vqs:
  	vdev->config->del_vqs(vdev);
  out_free_vb:
  	kfree(vb);
  out:
  	return err;
  }
  
  static void remove_common(struct virtio_balloon *vb)
  {
  	/* There might be pages left in the balloon: free them. */
  	while (vb->num_pages)
  		leak_balloon(vb, vb->num_pages);
  	update_balloon_size(vb);
  
  	/* Now we reset the device so we can clean up the queues. */
  	vb->vdev->config->reset(vb->vdev);
  
  	vb->vdev->config->del_vqs(vb->vdev);
  }
  
  static void virtballoon_remove(struct virtio_device *vdev)
  {
  	struct virtio_balloon *vb = vdev->priv;
  
  	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
  		virtio_balloon_unregister_shrinker(vb);
  	spin_lock_irq(&vb->stop_update_lock);
  	vb->stop_update = true;
  	spin_unlock_irq(&vb->stop_update_lock);
  	cancel_work_sync(&vb->update_balloon_size_work);
  	cancel_work_sync(&vb->update_balloon_stats_work);
  
  	remove_common(vb);
  #ifdef CONFIG_BALLOON_COMPACTION
  	if (vb->vb_dev_info.inode)
  		iput(vb->vb_dev_info.inode);
  
  	kern_unmount(balloon_mnt);
  #endif
  	kfree(vb);
  }
  
  #ifdef CONFIG_PM_SLEEP
  static int virtballoon_freeze(struct virtio_device *vdev)
  {
  	struct virtio_balloon *vb = vdev->priv;
  
  	/*
  	 * The workqueue is already frozen by the PM core before this
  	 * function is called.
  	 */
  	remove_common(vb);
  	return 0;
  }
  
  static int virtballoon_restore(struct virtio_device *vdev)
  {
  	struct virtio_balloon *vb = vdev->priv;
  	int ret;
  
  	ret = init_vqs(vdev->priv);
  	if (ret)
  		return ret;
  
  	virtio_device_ready(vdev);
  
  	if (towards_target(vb))
  		virtballoon_changed(vdev);
  	update_balloon_size(vb);
  	return 0;
  }
  #endif
  
  static int virtballoon_validate(struct virtio_device *vdev)
  {
  	__virtio_clear_bit(vdev, VIRTIO_F_IOMMU_PLATFORM);
  	return 0;
  }
  
  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 = {
  	.feature_table = features,
  	.feature_table_size = ARRAY_SIZE(features),
  	.driver.name =	KBUILD_MODNAME,
  	.driver.owner =	THIS_MODULE,
  	.id_table =	id_table,
  	.validate =	virtballoon_validate,
  	.probe =	virtballoon_probe,
  	.remove =	virtballoon_remove,
  	.config_changed = virtballoon_changed,
  #ifdef CONFIG_PM_SLEEP
  	.freeze	=	virtballoon_freeze,
  	.restore =	virtballoon_restore,
  #endif
  };
  
  module_virtio_driver(virtio_balloon_driver);
  MODULE_DEVICE_TABLE(virtio, id_table);
  MODULE_DESCRIPTION("Virtio balloon driver");
  MODULE_LICENSE("GPL");
  