[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) <pet...@infradead.org>
---
 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);