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1 | #ifndef CEPH_CRUSH_MAPPER_H |
2 | #define CEPH_CRUSH_MAPPER_H | |
3 | ||
4 | /* | |
5 | * CRUSH functions for find rules and then mapping an input to an | |
6 | * output set. | |
7 | * | |
11fdf7f2 | 8 | * LGPL2.1 |
7c673cae FG |
9 | */ |
10 | ||
11 | #include "crush.h" | |
12 | ||
13 | extern int crush_find_rule(const struct crush_map *map, int ruleset, int type, int size); | |
14 | /** @ingroup API | |
15 | * | |
16 | * Map __x__ to __result_max__ items and store them in the __result__ | |
17 | * array. The mapping is done by following each step of the rule | |
18 | * __ruleno__. See crush_make_rule(), crush_rule_set_step() and | |
19 | * crush_add_rule() for more information on how the rules are created, | |
20 | * populated and added to the crush __map__. | |
21 | * | |
22 | * The return value is the the number of items in the __result__ | |
23 | * array. If the caller asked for __result_max__ items and the return | |
24 | * value is X where X < __result_max__, the content of __result[0,X[__ | |
25 | * is defined but the content of __result[X,result_max[__ is | |
26 | * undefined. For example: | |
27 | * | |
28 | * crush_do_rule(map, ruleno=1, x=1, result, result_max=3,...) == 1 | |
29 | * result[0] is set | |
30 | * result[1] is undefined | |
31 | * result[2] is undefined | |
32 | * | |
33 | * An entry in the __result__ array is either an item in the crush | |
34 | * __map__ or ::CRUSH_ITEM_NONE if no item was found. For example: | |
35 | * | |
36 | * crush_do_rule(map, ruleno=1, x=1, result, result_max=4,...) == 2 | |
37 | * result[0] is CRUSH_ITEM_NONE | |
38 | * result[1] is item number 5 | |
39 | * result[2] is undefined | |
40 | * result[3] is undefined | |
41 | * | |
42 | * The __weight__ array contains the probabilities that a leaf is | |
43 | * ignored even if it is selected. It is a 16.16 fixed point | |
44 | * number in the range [0x00000,0x10000]. The lower the value, the | |
45 | * more often the leaf is ignored. For instance: | |
46 | * | |
47 | * - weight[leaf] == 0x00000 == 0.0 always ignore | |
48 | * - weight[leaf] == 0x10000 == 1.0 never ignore | |
49 | * - weight[leaf] == 0x08000 == 0.5 ignore 50% of the time | |
50 | * - weight[leaf] == 0x04000 == 0.25 ignore 75% of the time | |
51 | * - etc. | |
52 | * | |
53 | * During mapping, each leaf is checked against the __weight__ array, | |
54 | * using the leaf as an index. If there is no entry in __weight__ for | |
55 | * the leaf, it is ignored. If there is an entry, the leaf will be | |
56 | * ignored some of the time, depending on the probability. | |
57 | * | |
58 | * The __cwin__ argument must be set as follows: | |
59 | * | |
60 | * char __cwin__[crush_work_size(__map__, __result_max__)]; | |
61 | * crush_init_workspace(__map__, __cwin__); | |
62 | * | |
63 | * @param map the crush_map | |
64 | * @param ruleno a positive integer < __CRUSH_MAX_RULES__ | |
65 | * @param x the value to map to __result_max__ items | |
66 | * @param result an array of items of size __result_max__ | |
67 | * @param result_max the size of the __result__ array | |
68 | * @param weights an array of weights of size __weight_max__ | |
69 | * @param weight_max the size of the __weights__ array | |
70 | * @param cwin must be an char array initialized by crush_init_workspace | |
71 | * @param choose_args weights and ids for each known bucket | |
72 | * | |
73 | * @return 0 on error or the size of __result__ on success | |
74 | */ | |
75 | extern int crush_do_rule(const struct crush_map *map, | |
76 | int ruleno, | |
77 | int x, int *result, int result_max, | |
78 | const __u32 *weights, int weight_max, | |
79 | void *cwin, const struct crush_choose_arg *choose_args); | |
80 | ||
81 | /* Returns the exact amount of workspace that will need to be used | |
82 | for a given combination of crush_map and result_max. The caller can | |
83 | then allocate this much on its own, either on the stack, in a | |
84 | per-thread long-lived buffer, or however it likes. */ | |
85 | ||
86 | static inline size_t crush_work_size(const struct crush_map *map, | |
87 | int result_max) { | |
88 | return map->working_size + result_max * 3 * sizeof(__u32); | |
89 | } | |
90 | ||
91 | extern void crush_init_workspace(const struct crush_map *m, void *v); | |
92 | ||
93 | #endif |