1 files changed, 75 insertions, 5 deletions

diff --git a/include/linux/kref.h b/include/linux/kref.h
index d4a62ab2ee5e..1cbae9f2ef77 100644
--- a/include/linux/kref.h
+++ b/include/linux/kref.h
@@ -16,15 +16,85 @@
 #define _KREF_H_
 
 #include <linux/types.h>
+#include <linux/slab.h>
 
 struct kref {
         atomic_t refcount;
 };
 
-void kref_init(struct kref *kref);
-void kref_get(struct kref *kref);
-int kref_put(struct kref *kref, void (*release) (struct kref *kref));
-int kref_sub(struct kref *kref, unsigned int count,
-             void (*release) (struct kref *kref));
+/**
+ * kref_init - initialize object.
+ * @kref: object in question.
+ */
+static inline void kref_init(struct kref *kref)
+{
+        atomic_set(&kref->refcount, 1);
+        smp_mb();
+}
+
+/**
+ * kref_get - increment refcount for object.
+ * @kref: object.
+ */
+static inline void kref_get(struct kref *kref)
+{
+        WARN_ON(!atomic_read(&kref->refcount));
+        atomic_inc(&kref->refcount);
+        smp_mb__after_atomic_inc();
+}
+
+/**
+ * kref_put - decrement refcount for object.
+ * @kref: object.
+ * @release: pointer to the function that will clean up the object when the
+ *           last reference to the object is released.
+ *           This pointer is required, and it is not acceptable to pass kfree
+ *           in as this function.
+ *
+ * Decrement the refcount, and if 0, call release().
+ * Return 1 if the object was removed, otherwise return 0.  Beware, if this
+ * function returns 0, you still can not count on the kref from remaining in
+ * memory.  Only use the return value if you want to see if the kref is now
+ * gone, not present.
+ */
+static inline int kref_put(struct kref *kref, void (*release)(struct kref *kref))
+{
+        WARN_ON(release == NULL);
+        WARN_ON(release == (void (*)(struct kref *))kfree);
+
+        if (atomic_dec_and_test(&kref->refcount)) {
+                release(kref);
+                return 1;
+        }
+        return 0;
+}
+
+
+/**
+ * kref_sub - subtract a number of refcounts for object.
+ * @kref: object.
+ * @count: Number of recounts to subtract.
+ * @release: pointer to the function that will clean up the object when the
+ *           last reference to the object is released.
+ *           This pointer is required, and it is not acceptable to pass kfree
+ *           in as this function.
+ *
+ * Subtract @count from the refcount, and if 0, call release().
+ * Return 1 if the object was removed, otherwise return 0.  Beware, if this
+ * function returns 0, you still can not count on the kref from remaining in
+ * memory.  Only use the return value if you want to see if the kref is now
+ * gone, not present.
+ */
+static inline int kref_sub(struct kref *kref, unsigned int count,
+             void (*release)(struct kref *kref))
+{
+        WARN_ON(release == NULL);
+        WARN_ON(release == (void (*)(struct kref *))kfree);
 
+        if (atomic_sub_and_test((int) count, &kref->refcount)) {
+                release(kref);
+                return 1;
+        }
+        return 0;
+}
 #endif /* _KREF_H_ */