#ifndef CEPH_CRUSH_MAPPER_H #define CEPH_CRUSH_MAPPER_H /* * CRUSH functions for find rules and then mapping an input to an * output set. * * LGPL-2.1 or LGPL-3.0 */ #include "crush.h" /** @ingroup API * * Map __x__ to __result_max__ items and store them in the __result__ * array. The mapping is done by following each step of the rule * __ruleno__. See crush_make_rule(), crush_rule_set_step() and * crush_add_rule() for more information on how the rules are created, * populated and added to the crush __map__. * * The return value is the the number of items in the __result__ * array. If the caller asked for __result_max__ items and the return * value is X where X < __result_max__, the content of __result[0,X[__ * is defined but the content of __result[X,result_max[__ is * undefined. For example: * * crush_do_rule(map, ruleno=1, x=1, result, result_max=3,...) == 1 * result[0] is set * result[1] is undefined * result[2] is undefined * * An entry in the __result__ array is either an item in the crush * __map__ or ::CRUSH_ITEM_NONE if no item was found. For example: * * crush_do_rule(map, ruleno=1, x=1, result, result_max=4,...) == 2 * result[0] is CRUSH_ITEM_NONE * result[1] is item number 5 * result[2] is undefined * result[3] is undefined * * The __weight__ array contains the probabilities that a leaf is * ignored even if it is selected. It is a 16.16 fixed point * number in the range [0x00000,0x10000]. The lower the value, the * more often the leaf is ignored. For instance: * * - weight[leaf] == 0x00000 == 0.0 always ignore * - weight[leaf] == 0x10000 == 1.0 never ignore * - weight[leaf] == 0x08000 == 0.5 ignore 50% of the time * - weight[leaf] == 0x04000 == 0.25 ignore 75% of the time * - etc. * * During mapping, each leaf is checked against the __weight__ array, * using the leaf as an index. If there is no entry in __weight__ for * the leaf, it is ignored. If there is an entry, the leaf will be * ignored some of the time, depending on the probability. * * The __cwin__ argument must be set as follows: * * char __cwin__[crush_work_size(__map__, __result_max__)]; * crush_init_workspace(__map__, __cwin__); * * @param map the crush_map * @param ruleno a positive integer < __CRUSH_MAX_RULES__ * @param x the value to map to __result_max__ items * @param result an array of items of size __result_max__ * @param result_max the size of the __result__ array * @param weights an array of weights of size __weight_max__ * @param weight_max the size of the __weights__ array * @param cwin must be an char array initialized by crush_init_workspace * @param choose_args weights and ids for each known bucket * * @return 0 on error or the size of __result__ on success */ extern int crush_do_rule(const struct crush_map *map, int ruleno, int x, int *result, int result_max, const __u32 *weights, int weight_max, void *cwin, const struct crush_choose_arg *choose_args); /* Returns the exact amount of workspace that will need to be used for a given combination of crush_map and result_max. The caller can then allocate this much on its own, either on the stack, in a per-thread long-lived buffer, or however it likes. */ static inline size_t crush_work_size(const struct crush_map *map, int result_max) { return map->working_size + result_max * 3 * sizeof(__u32); } extern void crush_init_workspace(const struct crush_map *m, void *v); #endif