locking/atomic, kref: Implement kref_put_lock()

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@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2 files changed, 26 insertions, 11 deletions

diff --git a/include/linux/kref.h b/include/linux/kref.h
index 31c49a64cdf9..9db9685fed84 100644
--- a/include/linux/kref.h
+++ b/include/linux/kref.h
@@ -19,6 +19,7 @@
 #include <linux/atomic.h>
 #include <linux/kernel.h>
 #include <linux/mutex.h>
+#include <linux/spinlock.h>
 
 struct kref {
         atomic_t refcount;
@@ -86,12 +87,21 @@ static inline int kref_put_mutex(struct kref *kref,
                                  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;
         }
diff --git a/net/sunrpc/svcauth.c b/net/sunrpc/svcauth.c
index e112da8005b5..bb8db3cb8032 100644
--- a/net/sunrpc/svcauth.c
+++ b/net/sunrpc/svcauth.c
@@ -126,13 +126,18 @@ EXPORT_SYMBOL_GPL(svc_auth_unregister);
 static struct hlist_head        auth_domain_table[DN_HASHMAX];
 static DEFINE_SPINLOCK(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);