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From:   Qi Zheng <zhengqi.arch@bytedance.com>
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        linux-btrfs@vger.kernel.org, Qi Zheng <zhengqi.arch@bytedance.com>
Subject: [PATCH 10/29] vmw_balloon: dynamically allocate the vmw-balloon shrinker
Date:   Thu, 22 Jun 2023 16:53:16 +0800
Message-Id: <20230622085335.77010-11-zhengqi.arch@bytedance.com>
In-Reply-To: <20230622085335.77010-1-zhengqi.arch@bytedance.com>
References: <20230622085335.77010-1-zhengqi.arch@bytedance.com>
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In preparation for implementing lockless slab shrink,
we need to dynamically allocate the vmw-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 vmballoon.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
 drivers/misc/vmw_balloon.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
index 9ce9b9e0e9b6..2f86f666b476 100644
--- a/drivers/misc/vmw_balloon.c
+++ b/drivers/misc/vmw_balloon.c
@@ -380,7 +380,7 @@ struct vmballoon {
 	/**
 	 * @shrinker: shrinker interface that is used to avoid over-inflation.
 	 */
-	struct shrinker shrinker;
+	struct shrinker *shrinker;
 
 	/**
 	 * @shrinker_registered: whether the shrinker was registered.
@@ -1569,7 +1569,7 @@ static unsigned long vmballoon_shrinker_count(struct shrinker *shrinker,
 static void vmballoon_unregister_shrinker(struct vmballoon *b)
 {
 	if (b->shrinker_registered)
-		unregister_shrinker(&b->shrinker);
+		unregister_and_free_shrinker(b->shrinker);
 	b->shrinker_registered = false;
 }
 
@@ -1581,14 +1581,18 @@ static int vmballoon_register_shrinker(struct vmballoon *b)
 	if (!vmwballoon_shrinker_enable)
 		return 0;
 
-	b->shrinker.scan_objects = vmballoon_shrinker_scan;
-	b->shrinker.count_objects = vmballoon_shrinker_count;
-	b->shrinker.seeks = DEFAULT_SEEKS;
+	b->shrinker = shrinker_alloc_and_init(vmballoon_shrinker_count,
+					      vmballoon_shrinker_scan,
+					      0, DEFAULT_SEEKS, 0, b);
+	if (!b->shrinker)
+		return -ENOMEM;
 
-	r = register_shrinker(&b->shrinker, "vmw-balloon");
+	r = register_shrinker(b->shrinker, "vmw-balloon");
 
 	if (r == 0)
 		b->shrinker_registered = true;
+	else
+		shrinker_free(b->shrinker);
 
 	return r;
 }
-- 
2.30.2