1 files changed, 43 insertions, 0 deletions

diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
new file mode 100644
index 00000000000..a83833a1f7a
--- /dev/null
+++ b/include/linux/shrinker.h
@@ -0,0 +1,43 @@
+#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.
+ */
+struct shrink_control {
+        gfp_t gfp_mask;
+
+        /* How many slab objects shrinker() should scan and try to reclaim */
+        unsigned long nr_to_scan;
+};
+
+/*
+ * A callback you can register to apply pressure to ageable caches.
+ *
+ * 'sc' is passed shrink_control which includes a count 'nr_to_scan'
+ * and a 'gfpmask'.  It should look through the least-recently-used
+ * 'nr_to_scan' entries and attempt to free them up.  It should return
+ * the number of objects which remain in the cache.  If it returns -1, it means
+ * it cannot do any scanning at this time (eg. there is a risk of deadlock).
+ * The callback must not return -1 if nr_to_scan is zero.
+ *
+ * The 'gfpmask' refers to the allocation we are currently trying to
+ * fulfil.
+ *
+ * Note that 'shrink' will be passed nr_to_scan == 0 when the VM is
+ * querying the cache size, so a fastpath for that case is appropriate.
+ */
+struct shrinker {
+        int (*shrink)(struct shrinker *, struct shrink_control *sc);
+        int seeks;      /* seeks to recreate an obj */
+        long batch;     /* reclaim batch size, 0 = default */
+
+        /* These are for internal use */
+        struct list_head list;
+        long nr;        /* objs pending delete */
+};
+#define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
+extern void register_shrinker(struct shrinker *);
+extern void unregister_shrinker(struct shrinker *);
+#endif