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#ifndef CEPH_CRUSH_CRUSH_H
#define CEPH_CRUSH_CRUSH_H
#include <linux/types.h>
/*
* CRUSH is a pseudo-random data distribution algorithm that
* efficiently distributes input values (typically, data objects)
* across a heterogeneous, structured storage cluster.
*
* The algorithm was originally described in detail in this paper
* (although the algorithm has evolved somewhat since then):
*
* http://www.ssrc.ucsc.edu/Papers/weil-sc06.pdf
*
* LGPL2
*/
#define CRUSH_MAGIC 0x00010000ul /* for detecting algorithm revisions */
#define CRUSH_MAX_DEPTH 10 /* max crush hierarchy depth */
#define CRUSH_MAX_SET 10 /* max size of a mapping result */
/*
* CRUSH uses user-defined "rules" to describe how inputs should be
* mapped to devices. A rule consists of sequence of steps to perform
* to generate the set of output devices.
*/
struct crush_rule_step {
__u32 op;
__s32 arg1;
__s32 arg2;
};
/* step op codes */
enum {
CRUSH_RULE_NOOP = 0,
CRUSH_RULE_TAKE = 1, /* arg1 = value to start with */
CRUSH_RULE_CHOOSE_FIRSTN = 2, /* arg1 = num items to pick */
/* arg2 = type */
CRUSH_RULE_CHOOSE_INDEP = 3, /* same */
CRUSH_RULE_EMIT = 4, /* no args */
CRUSH_RULE_CHOOSE_LEAF_FIRSTN = 6,
CRUSH_RULE_CHOOSE_LEAF_INDEP = 7,
};
/*
* for specifying choose num (arg1) relative to the max parameter
* passed to do_rule
*/
#define CRUSH_CHOOSE_N 0
#define CRUSH_CHOOSE_N_MINUS(x) (-(x))
/*
* The rule mask is used to describe what the rule is intended for.
* Given a ruleset and size of output set, we search through the
* rule list for a matching rule_mask.
*/
struct crush_rule_mask {
__u8 ruleset;
__u8 type;
__u8 min_size;
__u8 max_size;
};
struct crush_rule {
__u32 len;
struct crush_rule_mask mask;
struct crush_rule_step steps[0];
};
#define crush_rule_size(len) (sizeof(struct crush_rule) + \
(len)*sizeof(struct crush_rule_step))
/*
* A bucket is a named container of other items (either devices or
* other buckets). Items within a bucket are chosen using one of a
* few different algorithms. The table summarizes how the speed of
* each option measures up against mapping stability when items are
* added or removed.
*
* Bucket Alg Speed Additions Removals
* ------------------------------------------------
* uniform O(1) poor poor
* list O(n) optimal poor
* tree O(log n) good good
* straw O(n) optimal optimal
*/
enum {
CRUSH_BUCKET_UNIFORM = 1,
CRUSH_BUCKET_LIST = 2,
CRUSH_BUCKET_TREE = 3,
CRUSH_BUCKET_STRAW = 4
};
extern const char *crush_bucket_alg_name(int alg);
struct crush_bucket {
__s32 id; /* this'll be negative */
__u16 type; /* non-zero; type=0 is reserved for devices */
__u8 alg; /* one of CRUSH_BUCKET_* */
__u8 hash; /* which hash function to use, CRUSH_HASH_* */
__u32 weight; /* 16-bit fixed point */
__u32 size; /* num items */
__s32 *items;
/*
* cached random permutation: used for uniform bucket and for
* the linear search fallback for the other bucket types.
*/
__u32 perm_x; /* @x for which *perm is defined */
__u32 perm_n; /* num elements of *perm that are permuted/defined */
__u32 *perm;
};
struct crush_bucket_uniform {
struct crush_bucket h;
__u32 item_weight; /* 16-bit fixed point; all items equally weighted */
};
struct crush_bucket_list {
struct crush_bucket h;
__u32 *item_weights; /* 16-bit fixed point */
__u32 *sum_weights; /* 16-bit fixed point. element i is sum
of weights 0..i, inclusive */
};
struct crush_bucket_tree {
struct crush_bucket h; /* note: h.size is _tree_ size, not number of
actual items */
__u8 num_nodes;
__u32 *node_weights;
};
struct crush_bucket_straw {
struct crush_bucket h;
__u32 *item_weights; /* 16-bit fixed point */
__u32 *straws; /* 16-bit fixed point */
};
/*
* CRUSH map includes all buckets, rules, etc.
*/
struct crush_map {
struct crush_bucket **buckets;
struct crush_rule **rules;
__s32 max_buckets;
__u32 max_rules;
__s32 max_devices;
};
/* crush.c */
extern int crush_get_bucket_item_weight(const struct crush_bucket *b, int pos);
extern void crush_destroy_bucket_uniform(struct crush_bucket_uniform *b);
extern void crush_destroy_bucket_list(struct crush_bucket_list *b);
extern void crush_destroy_bucket_tree(struct crush_bucket_tree *b);
extern void crush_destroy_bucket_straw(struct crush_bucket_straw *b);
extern void crush_destroy_bucket(struct crush_bucket *b);
extern void crush_destroy(struct crush_map *map);
#endif
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