+ * Due to frequent changes in the shrinker API the following
+ * compatibility wrappers should be used. They are as follows:
+ *
+ * SPL_SHRINKER_DECLARE is used to declare the shrinker which is
+ * passed to spl_register_shrinker()/spl_unregister_shrinker(). Use
+ * shrinker_name to set the shrinker variable name, shrinker_callback
+ * to set the callback function, and seek_cost to define the cost of
+ * reclaiming an object.
+ *
+ * SPL_SHRINKER_DECLARE(shrinker_name, shrinker_callback, seek_cost);
+ *
+ * SPL_SHRINKER_CALLBACK_FWD_DECLARE is used when a forward declaration
+ * of the shrinker callback function is required. Only the callback
+ * function needs to be passed.
+ *
+ * SPL_SHRINKER_CALLBACK_FWD_DECLARE(shrinker_callback);
+ *
+ * SPL_SHRINKER_CALLBACK_WRAPPER is used to declare the callback function
+ * which is registered with the shrinker. This function will call your
+ * custom shrinker which must use the following prototype. Notice the
+ * leading __'s, these must be appended to the callback_function name.
+ *
+ * int __shrinker_callback(struct shrinker *, struct shrink_control *)
+ * SPL_SHRINKER_CALLBACK_WRAPPER(shrinker_callback);a
+ *
+ *
+ * Example:
+ *
+ * SPL_SHRINKER_CALLBACK_FWD_DECLARE(my_shrinker_fn);
+ * SPL_SHRINKER_DECLARE(my_shrinker, my_shrinker_fn, 1);
+ *
+ * static int
+ * __my_shrinker_fn(struct shrinker *shrink, struct shrink_control *sc)
+ * {
+ * if (sc->nr_to_scan) {
+ * ...scan objects in the cache and reclaim them...
+ * }
+ *
+ * ...calculate number of objects in the cache...
+ *
+ * return (number of objects in the cache);
+ * }
+ * SPL_SHRINKER_CALLBACK_WRAPPER(my_shrinker_fn);