[RFC][PATCH 5/7] kref: Implement kref_put_lock()

[Peter Zijlstra]

Because home-rolling your own is _awesome_, stop doing it. Provide
kref_put_lock(), just like kref_put_mutex() but for a spinlock.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 include/linux/kref.h |   21 +++++++++++++++------
 net/sunrpc/svcauth.c |   15 ++++++++++-----
 2 files changed, 25 insertions(+), 11 deletions(-)

--- a/include/linux/kref.h
+++ b/include/linux/kref.h
@@ -86,12 +86,21 @@ static inline int kref_put_mutex(struct
 				 struct mutex *lock)
 {
 	WARN_ON(release == NULL);
-	if (unlikely(!atomic_add_unless(&kref->refcount, -1, 1))) {
-		mutex_lock(lock);
-		if (unlikely(!atomic_dec_and_test(&kref->refcount))) {
-			mutex_unlock(lock);
-			return 0;
-		}
+
+	if (atomic_dec_and_mutex_lock(&kref->refcount, lock)) {
+		release(kref);
+		return 1;
+	}
+	return 0;
+}
+
+static inline int kref_put_lock(struct kref *kref,
+				void (*release)(struct kref *kref),
+				spinlock_t *lock)
+{
+	WARN_ON(release == NULL);
+
+	if (atomic_dec_and_lock(&kref->refcount, lock)) {
 		release(kref);
 		return 1;
 	}
--- a/net/sunrpc/svcauth.c
+++ b/net/sunrpc/svcauth.c
@@ -127,13 +127,18 @@ static struct hlist_head	auth_domain_tab
 static spinlock_t	auth_domain_lock =
 	__SPIN_LOCK_UNLOCKED(auth_domain_lock);
 
+static void auth_domain_release(struct kref *kref)
+{
+	struct auth_domain *dom = container_of(kref, struct auth_domain, ref);
+
+	hlist_del(&dom->hash);
+	dom->flavour->domain_release(dom);
+	spin_unlock(&auth_domain_lock);
+}
+
 void auth_domain_put(struct auth_domain *dom)
 {
-	if (atomic_dec_and_lock(&dom->ref.refcount, &auth_domain_lock)) {
-		hlist_del(&dom->hash);
-		dom->flavour->domain_release(dom);
-		spin_unlock(&auth_domain_lock);
-	}
+	kref_put_lock(&dom->ref, auth_domain_release, &auth_domain_lock);
 }
 EXPORT_SYMBOL_GPL(auth_domain_put);