Merge tag 'fscache-fixes-20141013' of git://git.kernel.org/pub/scm/linux/kernel/git...

[sfrench/cifs-2.6.git] / include / linux / kref.h

diff --git a/include/linux/kref.h b/include/linux/kref.h
index e15828fd71f1b589780b933549e3b07c9652c1e9..484604d184be7380807868d9a12edc80e9064db3 100644 (file)
--- 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;
@@ -98,6 +99,38 @@ static inline int kref_put(struct kref *kref, void (*release)(struct kref *kref)
        return kref_sub(kref, 1, release);
 }
 
+/**
+ * kref_put_spinlock_irqsave - 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.
+ * @lock: lock to take in release case
+ *
+ * Behaves identical to kref_put with one exception.  If the reference count
+ * drops to zero, the lock will be taken atomically wrt dropping the reference
+ * count.  The release function has to call spin_unlock() without _irqrestore.
+ */
+static inline int kref_put_spinlock_irqsave(struct kref *kref,
+               void (*release)(struct kref *kref),
+               spinlock_t *lock)
+{
+       unsigned long flags;
+
+       WARN_ON(release == NULL);
+       if (atomic_add_unless(&kref->refcount, -1, 1))
+               return 0;
+       spin_lock_irqsave(lock, flags);
+       if (atomic_dec_and_test(&kref->refcount)) {
+               release(kref);
+               local_irq_restore(flags);
+               return 1;
+       }
+       spin_unlock_irqrestore(lock, flags);
+       return 0;
+}
+
 static inline int kref_put_mutex(struct kref *kref,
                                 void (*release)(struct kref *kref),
                                 struct mutex *lock)