linux-kernel - [PATCH 1/4] percpu-refcount: move zeroing of percpu part into percpu_ref_switch_to_atomic

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Message-Id: <20180918101946.13329-2-ming.lei@redhat.com>
Date:   Tue, 18 Sep 2018 18:19:43 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Ming Lei <ming.lei@...hat.com>, Tejun Heo <tj@...nel.org>,
        Jianchao Wang <jianchao.w.wang@...cle.com>,
        Kent Overstreet <kent.overstreet@...il.com>,
        linux-block@...r.kernel.org
Subject: [PATCH 1/4] percpu-refcount: move zeroing of percpu part into percpu_ref_switch_to_atomic_rcu

The percpu parts are added to atomic part in percpu_ref_switch_to_atomic_rcu(),
so it is readable & reasonable to clear them there.

Cc: Tejun Heo <tj@...nel.org>
Cc: Jianchao Wang <jianchao.w.wang@...cle.com>
Cc: Kent Overstreet <kent.overstreet@...il.com>
Cc: linux-block@...r.kernel.org
Signed-off-by: Ming Lei <ming.lei@...hat.com>
---
 lib/percpu-refcount.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c
index 9f96fa7bc000..a220b717f6bb 100644
--- a/lib/percpu-refcount.c
+++ b/lib/percpu-refcount.c
@@ -130,8 +130,10 @@ static void percpu_ref_switch_to_atomic_rcu(struct rcu_head *rcu)
 	unsigned long count = 0;
 	int cpu;
 
-	for_each_possible_cpu(cpu)
+	for_each_possible_cpu(cpu) {
 		count += *per_cpu_ptr(percpu_count, cpu);
+		*per_cpu_ptr(percpu_count, cpu) = 0;
+	}
 
 	pr_debug("global %ld percpu %ld",
 		 atomic_long_read(&ref->count), (long)count);
@@ -187,7 +189,6 @@ static void __percpu_ref_switch_to_atomic(struct percpu_ref *ref,
 static void __percpu_ref_switch_to_percpu(struct percpu_ref *ref)
 {
 	unsigned long __percpu *percpu_count = percpu_count_ptr(ref);
-	int cpu;
 
 	BUG_ON(!percpu_count);
 
@@ -202,9 +203,6 @@ static void __percpu_ref_switch_to_percpu(struct percpu_ref *ref)
 	 * zeroing is visible to all percpu accesses which can see the
 	 * following __PERCPU_REF_ATOMIC clearing.
 	 */
-	for_each_possible_cpu(cpu)
-		*per_cpu_ptr(percpu_count, cpu) = 0;
-
 	smp_store_release(&ref->percpu_count_ptr,
 			  ref->percpu_count_ptr & ~__PERCPU_REF_ATOMIC);
 }
-- 
2.9.5