[PATCH 11/29] virtio_balloon: dynamically allocate the virtio-balloon shrinker

Qi Zheng
2023-06-22T08:42:42Z

we need 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>
---
drivers/virtio/virtio_balloon.c | 26 ++++++++++++++++----------
1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 5b15936a5214..fa051bff8d90 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 +845,24 @@ static int virtio_balloon_oom_notify(struct notifier_block *nb,

static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
{
- unregister_shrinker(&vb->shrinker);
+ unregister_and_free_shrinker(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;
+ int ret;
+
+ vb->shrinker = shrinker_alloc_and_init(virtio_balloon_shrinker_count,
+ virtio_balloon_shrinker_scan,
+ 0, DEFAULT_SEEKS, 0, vb);
+ if (!vb->shrinker)
+ return -ENOMEM;
+
+ ret = register_shrinker(vb->shrinker, "virtio-balloon");
+ if (ret)
+ shrinker_free(vb->shrinker);

- return register_shrinker(&vb->shrinker, "virtio-balloon");
+ return ret;
}

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