static void leak_balloon(struct virtio_balloon *vb, size_t num)
{
struct page *page;
struct balloon_dev_info *vb_dev_info = vb->vb_dev_info;
/* We can only do one array worth at a time. */
num = min(num, ARRAY_SIZE(vb->pfns));
mutex_lock(&vb->balloon_lock);
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->pfns + vb->num_pfns, page);
vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
}
/*
* 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);
mutex_unlock(&vb->balloon_lock);
release_pages_by_pfn(vb->pfns, vb->num_pfns);
}
static void fill_balloon(struct virtio_balloon *vb, size_t num)
{
struct balloon_dev_info *vb_dev_info = vb->vb_dev_info;
/* We can only do one array worth at a time. */
num = min(num, ARRAY_SIZE(vb->pfns));
mutex_lock(&vb->balloon_lock);
for (vb->num_pfns = 0; vb->num_pfns < num;
vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
struct page *page = balloon_page_enqueue(vb_dev_info);
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;
}
set_page_pfns(vb->pfns + vb->num_pfns, page);
vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
adjust_managed_page_count(page, -1);
}
/* Did we get any? */
if (vb->num_pfns != 0)
tell_host(vb, vb->inflate_vq);
mutex_unlock(&vb->balloon_lock);
}
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;
}
/*
* virtballoon_migratepage - perform the balloon page migration on behalf of
* a compation thread. (called under page lock)
* @mapping: the page->mapping which will be assigned to the new migrated page.
* @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 address_space *mapping,
struct page *newpage, struct page *page, enum migrate_mode mode)
{
struct balloon_dev_info *vb_dev_info = balloon_page_device(page);
struct virtio_balloon *vb;
unsigned long flags;
BUG_ON(!vb_dev_info);
vb = vb_dev_info->balloon_device;
/*
* 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;
/* balloon's page migration 1st step -- inflate "newpage" */
spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
balloon_page_insert(newpage, mapping, &vb_dev_info->pages);
vb_dev_info->isolated_pages--;
spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
set_page_pfns(vb->pfns, newpage);
tell_host(vb, vb->inflate_vq);
/*
* balloon's page migration 2nd step -- deflate "page"
*
* It's safe to delete page->lru here because this page is at
* an isolated migration list, and this step is expected to happen here
*/
balloon_page_delete(page);
vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
set_page_pfns(vb->pfns, page);
tell_host(vb, vb->deflate_vq);
mutex_unlock(&vb->balloon_lock);
return MIGRATEPAGE_BALLOON_SUCCESS;
}
/*
* 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 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;
}
