ceph: CRUSH mapping algorithm
CRUSH is a pseudorandom data distribution function designed to map
inputs onto a dynamic hierarchy of devices, while minimizing the
extent to which inputs are remapped when the devices are added or
removed. It includes some features that are specifically useful for
storage, most notably the ability to map each input onto a set of N
devices that are separated across administrator-defined failure
domains. CRUSH is used to distribute data across the cluster of Ceph
storage nodes.
More information about CRUSH can be found in this paper:
http://www.ssrc.ucsc.edu/Papers/weil-sc06.pdf
Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/fs/ceph/crush/mapper.h b/fs/ceph/crush/mapper.h
new file mode 100644
index 0000000..98e9004
--- /dev/null
+++ b/fs/ceph/crush/mapper.h
@@ -0,0 +1,20 @@
+#ifndef _CRUSH_MAPPER_H
+#define _CRUSH_MAPPER_H
+
+/*
+ * CRUSH functions for find rules and then mapping an input to an
+ * output set.
+ *
+ * LGPL2
+ */
+
+#include "crush.h"
+
+extern int crush_find_rule(struct crush_map *map, int pool, int type, int size);
+extern int crush_do_rule(struct crush_map *map,
+ int ruleno,
+ int x, int *result, int result_max,
+ int forcefeed, /* -1 for none */
+ __u32 *weights);
+
+#endif