[PATCH v4 31/48] virtio_balloon: dynamically allocate the virtio-balloon shrinker

Qi Zheng
2023-08-07T11:20:48Z

In preparation for implementing lockless slab shrink, use new APIs to
dynamically allocate the virtio-balloon shrinker, so that it can be freed
asynchronously using kfree_rcu(). Then it doesn't need to wait for RCU
read-side critical section when releasing the struct virtio_balloon.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
---
drivers/virtio/virtio_balloon.c | 25 +++++++++++++++----------
1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 5b15936a5214..82e6087073a9 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -111,7 +111,7 @@ struct virtio_balloon {
struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];

/* Shrinker to return free pages - VIRTIO_BALLOON_F_FREE_PAGE_HINT */
- struct shrinker shrinker;
+ struct shrinker *shrinker;

/* OOM notifier to deflate on OOM - VIRTIO_BALLOON_F_DEFLATE_ON_OOM */
struct notifier_block oom_nb;
@@ -816,8 +816,7 @@ static unsigned long shrink_free_pages(struct virtio_balloon *vb,
static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
struct shrink_control *sc)
{
- struct virtio_balloon *vb = container_of(shrinker,
- struct virtio_balloon, shrinker);
+ struct virtio_balloon *vb = shrinker->private_data;

return shrink_free_pages(vb, sc->nr_to_scan);
}
@@ -825,8 +824,7 @@ static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
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);
+ struct virtio_balloon *vb = shrinker->private_data;

return vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
}
@@ -847,16 +845,23 @@ static int virtio_balloon_oom_notify(struct notifier_block *nb,

static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
{
- unregister_shrinker(&vb->shrinker);
+ shrinker_free(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;
+ vb->shrinker = shrinker_alloc(0, "virtio-balloon");
+ if (!vb->shrinker)
+ return -ENOMEM;

- return register_shrinker(&vb->shrinker, "virtio-balloon");
+ vb->shrinker->scan_objects = virtio_balloon_shrinker_scan;
+ vb->shrinker->count_objects = virtio_balloon_shrinker_count;
+ vb->shrinker->seeks = DEFAULT_SEEKS;
+ vb->shrinker->private_data = vb;
+
+ shrinker_register(vb->shrinker);
+
+ return 0;
}

static int virtballoon_probe(struct virtio_device *vdev)
--
2.30.2