1 files changed, 70 insertions, 0 deletions
diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
new file mode 100644
index 00000000000..68c097077ef
--- /dev/null
+++ b/include/linux/shrinker.h
@@ -0,0 +1,70 @@
+#ifndef _LINUX_SHRINKER_H
+#define _LINUX_SHRINKER_H
+
+/*
+ * This struct is used to pass information from page reclaim to the shrinkers.
+ * We consolidate the values for easier extention later.
+ *
+ * The 'gfpmask' refers to the allocation we are currently trying to
+ * fulfil.
+ */
+struct shrink_control {
+	gfp_t gfp_mask;
+
+	/*
+	 * How many objects scan_objects should scan and try to reclaim.
+	 * This is reset before every call, so it is safe for callees
+	 * to modify.
+	 */
+	unsigned long nr_to_scan;
+
+	/* shrink from these nodes */
+	nodemask_t nodes_to_scan;
+	/* current node being shrunk (for NUMA aware shrinkers) */
+	int nid;
+};
+
+#define SHRINK_STOP (~0UL)
+/*
+ * A callback you can register to apply pressure to ageable caches.
+ *
+ * @count_objects should return the number of freeable items in the cache. If
+ * there are no objects to free or the number of freeable items cannot be
+ * determined, it should return 0. No deadlock checks should be done during the
+ * count callback - the shrinker relies on aggregating scan counts that couldn't
+ * be executed due to potential deadlocks to be run at a later call when the
+ * deadlock condition is no longer pending.
+ *
+ * @scan_objects will only be called if @count_objects returned a non-zero
+ * value for the number of freeable objects. The callout should scan the cache
+ * and attempt to free items from the cache. It should then return the number
+ * of objects freed during the scan, or SHRINK_STOP if progress cannot be made
+ * due to potential deadlocks. If SHRINK_STOP is returned, then no further
+ * attempts to call the @scan_objects will be made from the current reclaim
+ * context.
+ *
+ * @flags determine the shrinker abilities, like numa awareness
+ */
+struct shrinker {
+	unsigned long (*count_objects)(struct shrinker *,
+				       struct shrink_control *sc);
+	unsigned long (*scan_objects)(struct shrinker *,
+				      struct shrink_control *sc);
+
+	int seeks;	/* seeks to recreate an obj */
+	long batch;	/* reclaim batch size, 0 = default */
+	unsigned long flags;
+
+	/* These are for internal use */
+	struct list_head list;
+	/* objs pending delete, per node */
+	atomic_long_t *nr_deferred;
+};
+#define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
+
+/* Flags */
+#define SHRINKER_NUMA_AWARE (1 << 0)
+
+extern int register_shrinker(struct shrinker *);
+extern void unregister_shrinker(struct shrinker *);
+#endif