linux-kernel - [PATCH rcu 2/3] rcu/kfree: Fix kfree_rcu_shrink

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Date:   Wed, 31 Aug 2022 11:09:20 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com,
        rostedt@...dmis.org,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Uladzislau Rezki <urezki@...il.com>,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: [PATCH rcu 2/3] rcu/kfree: Fix kfree_rcu_shrink_count() return value

From: "Joel Fernandes (Google)" <joel@...lfernandes.org>

As per the comments in include/linux/shrinker.h, .count_objects callback
should return the number of freeable items, but if there are no objects
to free, SHRINK_EMPTY should be returned. The only time 0 is returned
should be when we are unable to determine the number of objects, or the
cache should be skipped for another reason.

Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@...il.com>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/tree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index eb435941e92fd..3d234d536d4c3 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3372,7 +3372,7 @@ kfree_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
 		atomic_set(&krcp->backoff_page_cache_fill, 1);
 	}
 
-	return count;
+	return count == 0 ? SHRINK_EMPTY : count;
 }
 
 static unsigned long
-- 
2.31.1.189.g2e36527f23