[Qemu-devel] [PATCH v2 kernel 1/7] virtio-balloon: rework deflate to add page to a list

[Liang Li]

will allow faster notifications using a bitmap down the road.
balloon_pfn_to_page() can be removed because it's useless.

Signed-off-by: Liang Li <address@hidden>
Signed-off-by: Michael S. Tsirkin <address@hidden>
Cc: Paolo Bonzini <address@hidden>
Cc: Cornelia Huck <address@hidden>
Cc: Amit Shah <address@hidden>
---
 drivers/virtio/virtio_balloon.c | 22 ++++++++--------------
 1 file changed, 8 insertions(+), 14 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 476c0e3..8d649a2 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -98,12 +98,6 @@ static u32 page_to_balloon_pfn(struct page *page)
        return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
 }
 
-static struct page *balloon_pfn_to_page(u32 pfn)
-{
-       BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE);
-       return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE);
-}
-
 static void balloon_ack(struct virtqueue *vq)
 {
        struct virtio_balloon *vb = vq->vdev->priv;
@@ -176,18 +170,16 @@ static unsigned fill_balloon(struct virtio_balloon *vb, 
size_t num)
        return num_allocated_pages;
 }
 
-static void release_pages_balloon(struct virtio_balloon *vb)
+static void release_pages_balloon(struct virtio_balloon *vb,
+                                struct list_head *pages)
 {
-       unsigned int i;
-       struct page *page;
+       struct page *page, *next;
 
-       /* Find pfns pointing at start of each page, get pages and free them. */
-       for (i = 0; i < vb->num_pfns; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
-               page = balloon_pfn_to_page(virtio32_to_cpu(vb->vdev,
-                                                          vb->pfns[i]));
+       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 */
        }
 }
@@ -197,6 +189,7 @@ 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));
@@ -208,6 +201,7 @@ static unsigned leak_balloon(struct virtio_balloon *vb, 
size_t num)
                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;
        }
 
@@ -219,7 +213,7 @@ static unsigned leak_balloon(struct virtio_balloon *vb, 
size_t num)
         */
        if (vb->num_pfns != 0)
                tell_host(vb, vb->deflate_vq);
-       release_pages_balloon(vb);
+       release_pages_balloon(vb, &pages);
        mutex_unlock(&vb->balloon_lock);
        return num_freed_pages;
 }
-- 
1.8.3.1