linux-ext4 - [PATCH 11/29] virtio_balloon: dynamically allocate the virtio-balloon shrinker

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Date:   Thu, 22 Jun 2023 08:39:14 +0000
From:   Qi Zheng <qi.zheng@...ux.dev>
To:     akpm@...ux-foundation.org, david@...morbit.com, tkhai@...ru,
        vbabka@...e.cz, roman.gushchin@...ux.dev, djwong@...nel.org,
        brauner@...nel.org, paulmck@...nel.org, tytso@....edu
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        dm-devel@...hat.com, linux-raid@...r.kernel.org,
        linux-bcache@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-nfs@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-btrfs@...r.kernel.org, Qi Zheng <zhengqi.arch@...edance.com>
Subject: [PATCH 11/29] virtio_balloon: dynamically allocate the virtio-balloon shrinker

From: Qi Zheng <zhengqi.arch@...edance.com>

In preparation for implementing lockless slab shrink,
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@...edance.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