crush: add SET_CHOOSELEAF_VARY_R step

This lets you adjust the vary_r tunable on a per-rule basis.

Reflects ceph.git commit f944ccc20aee60a7d8da7e405ec75ad1cd449fac.
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

include/linux/crush/crush.h

@@ -51,6 +51,7 @@ enum {
 	CRUSH_RULE_SET_CHOOSELEAF_TRIES = 9, /* override chooseleaf_descend_once */
 	CRUSH_RULE_SET_CHOOSE_LOCAL_TRIES = 10,
 	CRUSH_RULE_SET_CHOOSE_LOCAL_FALLBACK_TRIES = 11,
+	CRUSH_RULE_SET_CHOOSELEAF_VARY_R = 12
 };
 
 /*

net/ceph/crush/mapper.c

@@ -709,6 +709,11 @@ int crush_do_rule(const struct crush_map *map,
 				choose_local_fallback_retries = curstep->arg1;
 			break;
 
+		case CRUSH_RULE_SET_CHOOSELEAF_VARY_R:
+			if (curstep->arg1 >= 0)
+				vary_r = curstep->arg1;
+			break;
+
 		case CRUSH_RULE_CHOOSELEAF_FIRSTN:
 		case CRUSH_RULE_CHOOSE_FIRSTN:
 			firstn = 1;