libceph, crush: per-pool crush_choose_arg_map for crush_do_rule()

If there is no crush_choose_arg_map for a given pool, a NULL pointer is
passed to preserve existing crush_do_rule() behavior.

Reflects ceph.git commits 55fb91d64071552ea1bc65ab4ea84d3c8b73ab4b,
                          dbe36e08be00c6519a8c89718dd47b0219c20516.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

include/linux/crush/crush.h

@@ -2,6 +2,7 @@
 #define CEPH_CRUSH_CRUSH_H
 
 #ifdef __KERNEL__
+# include <linux/rbtree.h>
 # include <linux/types.h>
 #else
 # include "crush_compat.h"
@@ -190,6 +191,10 @@ struct crush_choose_arg {
  *
  */
 struct crush_choose_arg_map {
+#ifdef __KERNEL__
+	struct rb_node node;
+	u64 choose_args_index;
+#endif
 	struct crush_choose_arg *args; /*!< replacement for each bucket
                                             in the crushmap */
 	__u32 size;                    /*!< size of the __args__ array */
@@ -294,6 +299,9 @@ struct crush_map {
 	__u32 allowed_bucket_algs;
 
 	__u32 *choose_tries;
+#else
+	/* CrushWrapper::choose_args */
+	struct rb_root choose_args;
 #endif
 };