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Subject: [RFC for Linux v4 2/2] virtio_balloon: Add deflate_cont_vq to deflate continuous pages
This commit adds a vq deflate_cont_vq to deflate continuous pages.
When VIRTIO_BALLOON_F_CONT_PAGES is set, call leak_balloon_cont to leak
the balloon.
leak_balloon_cont will call balloon_page_list_dequeue_cont get continuous
pages from balloon and report them use deflate_cont_vq.
Signed-off-by: Hui Zhu <teawaterz@linux.alibaba.com>
---
drivers/virtio/virtio_balloon.c | 73 ++++++++++++++++++++++++++++++++----
include/linux/balloon_compaction.h | 3 ++
mm/balloon_compaction.c | 76 ++++++++++++++++++++++++++++++++++++++
3 files changed, 144 insertions(+), 8 deletions(-)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index b89f566..258b3d9 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -44,6 +44,7 @@
#define VIRTIO_BALLOON_INFLATE_MAX_ORDER min((int) (sizeof(__virtio32) * BITS_PER_BYTE - \
1 - PAGE_SHIFT), (MAX_ORDER-1))
+#define VIRTIO_BALLOON_DEFLATE_MAX_PAGES_NUM (((__virtio32)~0U) >> PAGE_SHIFT)
#ifdef CONFIG_BALLOON_COMPACTION
static struct vfsmount *balloon_mnt;
@@ -56,6 +57,7 @@ enum virtio_balloon_vq {
VIRTIO_BALLOON_VQ_FREE_PAGE,
VIRTIO_BALLOON_VQ_REPORTING,
VIRTIO_BALLOON_VQ_INFLATE_CONT,
+ VIRTIO_BALLOON_VQ_DEFLATE_CONT,
VIRTIO_BALLOON_VQ_MAX
};
@@ -65,7 +67,8 @@ enum virtio_balloon_config_read {
struct virtio_balloon {
struct virtio_device *vdev;
- struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq, *inflate_cont_vq;
+ struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq,
+ *inflate_cont_vq, *deflate_cont_vq;
/* Balloon's own wq for cpu-intensive work items */
struct workqueue_struct *balloon_wq;
@@ -215,6 +218,16 @@ static void set_page_pfns(struct virtio_balloon *vb,
page_to_balloon_pfn(page) + i);
}
+static void set_page_pfns_size(struct virtio_balloon *vb,
+ __virtio32 pfns[], struct page *page,
+ size_t size)
+{
+ /* Set the first pfn of the continuous pages. */
+ pfns[0] = cpu_to_virtio32(vb->vdev, page_to_balloon_pfn(page));
+ /* Set the size of the continuous pages. */
+ pfns[1] = (__virtio32) size;
+}
+
static void set_page_pfns_order(struct virtio_balloon *vb,
__virtio32 pfns[], struct page *page,
unsigned int order)
@@ -222,10 +235,7 @@ static void set_page_pfns_order(struct virtio_balloon *vb,
if (order == 0)
return set_page_pfns(vb, pfns, page);
- /* Set the first pfn of the continuous pages. */
- pfns[0] = cpu_to_virtio32(vb->vdev, page_to_balloon_pfn(page));
- /* Set the size of the continuous pages. */
- pfns[1] = PAGE_SIZE << order;
+ set_page_pfns_size(vb, pfns, page, PAGE_SIZE << order);
}
static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
@@ -367,6 +377,42 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
return num_freed_pages;
}
+static unsigned int leak_balloon_cont(struct virtio_balloon *vb, size_t num)
+{
+ unsigned int num_freed_pages;
+ struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
+ LIST_HEAD(pages);
+ size_t num_pages;
+
+ mutex_lock(&vb->balloon_lock);
+ for (vb->num_pfns = 0, num_freed_pages = 0;
+ vb->num_pfns < ARRAY_SIZE(vb->pfns) && num_freed_pages < num;
+ vb->num_pfns += 2,
+ num_freed_pages += num_pages << (PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT)) {
+ struct page *page;
+
+ num_pages = balloon_page_list_dequeue_cont(vb_dev_info, &pages, &page,
+ min_t(size_t,
+ VIRTIO_BALLOON_DEFLATE_MAX_PAGES_NUM,
+ num - num_freed_pages));
+ if (!num_pages)
+ break;
+ set_page_pfns_size(vb, vb->pfns + vb->num_pfns, page, num_pages << PAGE_SHIFT);
+ }
+ vb->num_pages -= num_freed_pages;
+
+ /*
+ * 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_cont_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)
{
@@ -551,8 +597,12 @@ static void update_balloon_size_func(struct work_struct *work)
if (diff > 0)
diff -= fill_balloon(vb, diff);
- else
- diff += leak_balloon(vb, -diff);
+ else {
+ if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_CONT_PAGES))
+ diff += leak_balloon_cont(vb, -diff);
+ else
+ diff += leak_balloon(vb, -diff);
+ }
update_balloon_size(vb);
if (diff)
@@ -587,6 +637,8 @@ static int init_vqs(struct virtio_balloon *vb)
names[VIRTIO_BALLOON_VQ_REPORTING] = NULL;
names[VIRTIO_BALLOON_VQ_INFLATE_CONT] = NULL;
callbacks[VIRTIO_BALLOON_VQ_INFLATE_CONT] = NULL;
+ names[VIRTIO_BALLOON_VQ_DEFLATE_CONT] = NULL;
+ callbacks[VIRTIO_BALLOON_VQ_DEFLATE_CONT] = NULL;
if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
names[VIRTIO_BALLOON_VQ_STATS] = "stats";
@@ -606,6 +658,8 @@ static int init_vqs(struct virtio_balloon *vb)
if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_CONT_PAGES)) {
names[VIRTIO_BALLOON_VQ_INFLATE_CONT] = "inflate_cont";
callbacks[VIRTIO_BALLOON_VQ_INFLATE_CONT] = balloon_ack;
+ names[VIRTIO_BALLOON_VQ_DEFLATE_CONT] = "deflate_cont";
+ callbacks[VIRTIO_BALLOON_VQ_DEFLATE_CONT] = balloon_ack;
}
err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX,
@@ -643,9 +697,12 @@ static int init_vqs(struct virtio_balloon *vb)
if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
vb->reporting_vq = vqs[VIRTIO_BALLOON_VQ_REPORTING];
- if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_CONT_PAGES))
+ if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_CONT_PAGES)) {
vb->inflate_cont_vq
= vqs[VIRTIO_BALLOON_VQ_INFLATE_CONT];
+ vb->deflate_cont_vq
+ = vqs[VIRTIO_BALLOON_VQ_DEFLATE_CONT];
+ }
return 0;
}
diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h
index 8180bbf..7cb2a75 100644
--- a/include/linux/balloon_compaction.h
+++ b/include/linux/balloon_compaction.h
@@ -70,6 +70,9 @@ extern size_t balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info,
struct list_head *pages);
extern size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info,
struct list_head *pages, size_t n_req_pages);
+extern size_t balloon_page_list_dequeue_cont(struct balloon_dev_info *b_dev_info,
+ struct list_head *pages, struct page **first_page,
+ size_t max_req_pages);
static inline struct page *balloon_page_alloc(void)
{
diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
index 397d0b9..ea7d91f 100644
--- a/mm/balloon_compaction.c
+++ b/mm/balloon_compaction.c
@@ -111,6 +111,82 @@ size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info,
}
EXPORT_SYMBOL_GPL(balloon_page_list_dequeue);
+/**
+ * balloon_page_list_dequeue_cont() - removes continuous pages from balloon's page list
+ * and returns a list of the continuous pages.
+ * @b_dev_info: balloon device decriptor where we will grab a page from.
+ * @pages: pointer to the list of pages that would be returned to the caller.
+ * @max_req_pages: max number of requested pages.
+ *
+ * Driver must call this function to properly de-allocate a previous enlisted
+ * balloon pages before definitively releasing it back to the guest system.
+ * This function tries to remove @max_req_pages continuous pages from the ballooned
+ * pages and return them to the caller in the @pages list.
+ *
+ * Note that this function may fail to dequeue some pages even if the balloon
+ * isn't empty - since the page list can be temporarily empty due to compaction
+ * of isolated pages.
+ *
+ * Return: number of pages that were added to the @pages list.
+ */
+size_t balloon_page_list_dequeue_cont(struct balloon_dev_info *b_dev_info,
+ struct list_head *pages, struct page **first_page,
+ size_t max_req_pages)
+{
+ struct page *page, *tmp;
+ unsigned long flags, tail_pfn;
+ size_t n_pages = 0;
+ bool got_first = false;
+
+ spin_lock_irqsave(&b_dev_info->pages_lock, flags);
+ list_for_each_entry_safe_reverse(page, tmp, &b_dev_info->pages, lru) {
+ unsigned long pfn;
+
+ if (n_pages == max_req_pages)
+ break;
+
+ pfn = page_to_pfn(page);
+
+ if (got_first && pfn != tail_pfn + 1)
+ break;
+
+ /*
+ * Block others from accessing the 'page' while we get around to
+ * establishing additional references and preparing the 'page'
+ * to be released by the balloon driver.
+ */
+ if (!trylock_page(page)) {
+ if (!got_first)
+ continue;
+ else
+ break;
+ }
+
+ if (IS_ENABLED(CONFIG_BALLOON_COMPACTION) && PageIsolated(page)) {
+ /* raced with isolation */
+ unlock_page(page);
+ if (!got_first)
+ continue;
+ else
+ break;
+ }
+ balloon_page_delete(page);
+ __count_vm_event(BALLOON_DEFLATE);
+ list_add(&page->lru, pages);
+ unlock_page(page);
+ n_pages++;
+ tail_pfn = pfn;
+ if (!got_first) {
+ got_first = true;
+ *first_page = page;
+ }
+ }
+ spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
+
+ return n_pages;
+}
+EXPORT_SYMBOL_GPL(balloon_page_list_dequeue_cont);
+
/*
* balloon_pages_alloc - allocates a new page for insertion into the balloon
* page list.
--
2.7.4
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