lockref: Add lockref_put_not_zero

Put a lockref unless the lockref is dead or its count would become zero.
This is the same as lockref_put_or_lock except that the lock is never
left held.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>

diff --git a/include/linux/lockref.h b/include/linux/lockref.h
index 2eac32095113177ba60493b956f44b97e525d471..99f17cc8e16300e89c23a95403b2a0712939a771 100644 (file)
--- a/include/linux/lockref.h
+++ b/include/linux/lockref.h
@@ -37,6 +37,7 @@ struct lockref {
 extern void lockref_get(struct lockref *);
 extern int lockref_put_return(struct lockref *);
 extern int lockref_get_not_zero(struct lockref *);
+extern int lockref_put_not_zero(struct lockref *);
 extern int lockref_get_or_lock(struct lockref *);
 extern int lockref_put_or_lock(struct lockref *);
 

diff --git a/lib/lockref.c b/lib/lockref.c
index 47169ed7e964f53dbc7735a3ad5b19c492878f45..3d468b53d4c931de6d76d0f51be6a07b3a066ecf 100644 (file)
--- a/lib/lockref.c
+++ b/lib/lockref.c
@@ -80,6 +80,34 @@ int lockref_get_not_zero(struct lockref *lockref)
 }
 EXPORT_SYMBOL(lockref_get_not_zero);
 
+/**
+ * lockref_put_not_zero - Decrements count unless count <= 1 before decrement
+ * @lockref: pointer to lockref structure
+ * Return: 1 if count updated successfully or 0 if count would become zero
+ */
+int lockref_put_not_zero(struct lockref *lockref)
+{
+       int retval;
+
+       CMPXCHG_LOOP(
+               new.count--;
+               if (old.count <= 1)
+                       return 0;
+       ,
+               return 1;
+       );
+
+       spin_lock(&lockref->lock);
+       retval = 0;
+       if (lockref->count > 1) {
+               lockref->count--;
+               retval = 1;
+       }
+       spin_unlock(&lockref->lock);
+       return retval;
+}
+EXPORT_SYMBOL(lockref_put_not_zero);
+
 /**
  * lockref_get_or_lock - Increments count unless the count is 0 or dead
  * @lockref: pointer to lockref structure