linux-kernel - [PATCHv2 2/2] kref: introduce __kref_put

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Date:   Mon, 13 Nov 2023 15:48:09 -0500
From:   Alexander Aring <aahringo@...hat.com>
To:     peterz@...radead.org
Cc:     will@...nel.org, gfs2@...ts.linux.dev, aahringo@...hat.com,
        boqun.feng@...il.com, mark.rutland@....com,
        linux-kernel@...r.kernel.org
Subject: [PATCHv2 2/2] kref: introduce __kref_put_lock macro

This patch introduce the __kref_put_lock macro to easily write a
kref_put_lock functionality based on refcount_dec_and_lock functions.
Existing per lock type specific kref_put_lock functionality are updated
to use the new __kref_put_lock macro.

Co-developed: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Alexander Aring <aahringo@...hat.com>
---
 include/linux/kref.h | 37 +++++++++++++++++++++++++++----------
 1 file changed, 27 insertions(+), 10 deletions(-)

diff --git a/include/linux/kref.h b/include/linux/kref.h
index d32e21a2538c..d8e26ac1d54f 100644
--- a/include/linux/kref.h
+++ b/include/linux/kref.h
@@ -68,26 +68,43 @@ static inline int kref_put(struct kref *kref, void (*release)(struct kref *kref)
 	return 0;
 }
 
+/**
+ * __kref_dec_and_lock - macro to create code to holding a lock and call the
+ *                       release callback if being able to decremnt refcount
+ *                       to 0
+ * @kref: the kref
+ * @_release: callback for the release function
+ * @_ref_dec_and_lock: ref_and_lock lock specific function call code
+ *
+ * The result will be directly returned as a right operand operation. Uusally
+ * the caller use it directly after a return statement.
+ */
+#define __kref_put_lock(_kref, _release, _ref_dec_and_lock)	\
+({								\
+	int _ret = 0;						\
+								\
+	if (_ref_dec_and_lock) {				\
+		_release(kref);					\
+		_ret = 1;					\
+	}							\
+								\
+	_ret;							\
+})
+
 static inline int kref_put_mutex(struct kref *kref,
 				 void (*release)(struct kref *kref),
 				 struct mutex *lock)
 {
-	if (refcount_dec_and_mutex_lock(&kref->refcount, lock)) {
-		release(kref);
-		return 1;
-	}
-	return 0;
+	return __kref_put_lock(kref, release,
+			       refcount_dec_and_mutex_lock(&kref->refcount, lock));
 }
 
 static inline int kref_put_lock(struct kref *kref,
 				void (*release)(struct kref *kref),
 				spinlock_t *lock)
 {
-	if (refcount_dec_and_lock(&kref->refcount, lock)) {
-		release(kref);
-		return 1;
-	}
-	return 0;
+	return __kref_put_lock(kref, release,
+			       refcount_dec_and_lock(&kref->refcount, lock));
 }
 
 /**
-- 
2.39.3