[PATCH 2/2] virtio_balloon: divide/multiply instead of shifts

Michael S. Tsirkin
2019-11-19T10:29:41Z

We managed to get confused about the shift direction at least once.
Let's switch to division/multiplcation instead. Add a number of pages
macro for this purpose. We still keep the order macro around too since
this is what alloc/free pages want.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
drivers/virtio/virtio_balloon.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index b6a95cd28d9f..dc1ebd638e9b 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -36,6 +36,7 @@
/* The size of a free page block in bytes */
#define VIRTIO_BALLOON_HINT_BLOCK_BYTES \
(1 << (VIRTIO_BALLOON_HINT_BLOCK_ORDER + PAGE_SHIFT))
+#define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER)

#ifdef CONFIG_BALLOON_COMPACTION
static struct vfsmount *balloon_mnt;
@@ -765,11 +766,11 @@ static unsigned long shrink_free_pages(struct virtio_balloon *vb,
unsigned long blocks_to_free, blocks_freed;

pages_to_free = round_up(pages_to_free,
- 1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER);
- blocks_to_free = pages_to_free >> VIRTIO_BALLOON_HINT_BLOCK_ORDER;
+ VIRTIO_BALLOON_HINT_BLOCK_PAGES);
+ blocks_to_free = pages_to_free / VIRTIO_BALLOON_HINT_BLOCK_PAGES;
blocks_freed = return_free_pages_to_mm(vb, blocks_to_free);

- return blocks_freed << VIRTIO_BALLOON_HINT_BLOCK_ORDER;
+ return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
}

static unsigned long leak_balloon_pages(struct virtio_balloon *vb,
@@ -825,7 +826,7 @@ static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
unsigned long count;

count = vb->num_pages / VIRTIO_BALLOON_PAGES_PER_PAGE;
- count += vb->num_free_page_blocks << VIRTIO_BALLOON_HINT_BLOCK_ORDER;
+ count += vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES;

return count;
}
--
MST