1 files changed, 33 insertions, 13 deletions

diff --git a/lib/kref.c b/lib/kref.c
index 9ecd6e865610..3efb882b11db 100644
--- a/lib/kref.c
+++ b/lib/kref.c
@@ -13,17 +13,7 @@
 
 #include <linux/kref.h>
 #include <linux/module.h>
-
-/**
- * kref_set - initialize object and set refcount to requested number.
- * @kref: object in question.
- * @num: initial reference counter
- */
-void kref_set(struct kref *kref, int num)
-{
-        atomic_set(&kref->refcount, num);
-        smp_mb();
-}
+#include <linux/slab.h>
 
 /**
  * kref_init - initialize object.
@@ -31,7 +21,8 @@ void kref_set(struct kref *kref, int num)
  */
 void kref_init(struct kref *kref)
 {
-        kref_set(kref, 1);
+        atomic_set(&kref->refcount, 1);
+        smp_mb();
 }
 
 /**
@@ -71,7 +62,36 @@ int kref_put(struct kref *kref, void (*release)(struct kref *kref))
         return 0;
 }
 
-EXPORT_SYMBOL(kref_set);
+
+/**
+ * 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.
+ */
+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;
+}
+
 EXPORT_SYMBOL(kref_init);
 EXPORT_SYMBOL(kref_get);
 EXPORT_SYMBOL(kref_put);
+EXPORT_SYMBOL(kref_sub);