linux-kernel - [PATCH V8 5/8] percpu-refcount: introduce __percpu_ref_tryget

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Date:   Tue,  3 Oct 2017 22:04:03 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Jens Axboe <axboe@...com>, linux-block@...r.kernel.org,
        Christoph Hellwig <hch@...radead.org>,
        linux-scsi@...r.kernel.org,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>
Cc:     Bart Van Assche <bart.vanassche@...disk.com>,
        Oleksandr Natalenko <oleksandr@...alenko.name>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        Cathy Avery <cavery@...hat.com>,
        Martin Steigerwald <martin@...htvoll.de>,
        linux-kernel@...r.kernel.org, Hannes Reinecke <hare@...e.com>,
        Ming Lei <ming.lei@...hat.com>,
        Bart Van Assche <Bart.VanAssche@....com>,
        Tejun Heo <tj@...nel.org>
Subject: [PATCH V8 5/8] percpu-refcount: introduce __percpu_ref_tryget_live

Block layer need to call this function after holding
rcu lock in a real hot path, so introduce this helper.

Cc: Bart Van Assche <Bart.VanAssche@....com>
Cc: Tejun Heo <tj@...nel.org>
Signed-off-by: Ming Lei <ming.lei@...hat.com>
---
 include/linux/percpu-refcount.h | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
index c13dceb87b60..a0f22586a28d 100644
--- a/include/linux/percpu-refcount.h
+++ b/include/linux/percpu-refcount.h
@@ -221,6 +221,21 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref)
 	return ret;
 }
 
+static inline bool __percpu_ref_tryget_live(struct percpu_ref *ref)
+{
+	unsigned long __percpu *percpu_count;
+	bool ret = false;
+
+	if (__ref_is_percpu(ref, &percpu_count)) {
+		this_cpu_inc(*percpu_count);
+		ret = true;
+	} else if (!(ref->percpu_count_ptr & __PERCPU_REF_DEAD)) {
+		ret = atomic_long_inc_not_zero(&ref->count);
+	}
+
+	return ret;
+}
+
 /**
  * percpu_ref_tryget_live - try to increment a live percpu refcount
  * @ref: percpu_ref to try-get
@@ -238,18 +253,10 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref)
  */
 static inline bool percpu_ref_tryget_live(struct percpu_ref *ref)
 {
-	unsigned long __percpu *percpu_count;
-	bool ret = false;
+	bool ret;
 
 	rcu_read_lock_sched();
-
-	if (__ref_is_percpu(ref, &percpu_count)) {
-		this_cpu_inc(*percpu_count);
-		ret = true;
-	} else if (!(ref->percpu_count_ptr & __PERCPU_REF_DEAD)) {
-		ret = atomic_long_inc_not_zero(&ref->count);
-	}
-
+	ret = __percpu_ref_tryget_live(ref);
 	rcu_read_unlock_sched();
 
 	return ret;
-- 
2.9.5