Received-SPF: pass (google.com: domain of linux-ext4-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Qi Zheng <zhengqi.arch@bytedance.com>
To:     akpm@linux-foundation.org, david@fromorbit.com, tkhai@ya.ru,
        vbabka@suse.cz, roman.gushchin@linux.dev, djwong@kernel.org,
        brauner@kernel.org, paulmck@kernel.org, tytso@mit.edu,
        steven.price@arm.com, cel@kernel.org, senozhatsky@chromium.org,
        yujie.liu@intel.com, gregkh@linuxfoundation.org,
        muchun.song@linux.dev
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org,
        kvm@vger.kernel.org, xen-devel@lists.xenproject.org,
        linux-erofs@lists.ozlabs.org,
        linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com,
        linux-nfs@vger.kernel.org, linux-mtd@lists.infradead.org,
        rcu@vger.kernel.org, netdev@vger.kernel.org,
        dri-devel@lists.freedesktop.org, linux-arm-msm@vger.kernel.org,
        dm-devel@redhat.com, linux-raid@vger.kernel.org,
        linux-bcache@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
        linux-xfs@vger.kernel.org, linux-btrfs@vger.kernel.org,
        Qi Zheng <zhengqi.arch@bytedance.com>
Subject: [PATCH v2 30/47] virtio_balloon: dynamically allocate the virtio-balloon shrinker
Date:   Mon, 24 Jul 2023 17:43:37 +0800
Message-Id: <20230724094354.90817-31-zhengqi.arch@bytedance.com>
In-Reply-To: <20230724094354.90817-1-zhengqi.arch@bytedance.com>
References: <20230724094354.90817-1-zhengqi.arch@bytedance.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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>
---
 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..d773860c3b18 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_unregister(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