#ifndef CEPH_CRUSH_CRUSH_H
#define CEPH_CRUSH_CRUSH_H
#ifdef __KERNEL__
# include <linux/types.h>
#else
# include "crush_compat.h"
#endif
/*
* 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_RULESET (1<<8) /* max crush ruleset number */
#define CRUSH_MAX_RULES CRUSH_MAX_RULESET /* should be the same as max rulesets */
#define CRUSH_MAX_DEVICE_WEIGHT (100u * 0x10000u)
#define CRUSH_MAX_BUCKET_WEIGHT (65535u * 0x10000u)
#define CRUSH_ITEM_UNDEF 0x7ffffffe /* undefined result (internal use only) */
#define CRUSH_ITEM_NONE 0x7fffffff /* no 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_CHOOSELEAF_FIRSTN = 6,
CRUSH_RULE_CHOOSELEAF_INDEP = 7,
CRUSH_RULE_SET_CHOOSE_TRIES = 8, /* override choose_total_tries */
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,
CRUSH_RULE_SET_CHOOSELEAF_STABLE = 13
};
/*
* 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) better better
* straw2 O(n) optimal optimal
*/
enum {
CRUSH_BUCKET_UNIFORM = 1,
CRUSH_BUCKET_LIST = 2,
CRUSH_BUCKET_TREE = 3,
CRUSH_BUCKET_STRAW = 4,
CRUSH_BUCKET_STRAW2 = 5,
};
extern const char *crush_bucket_alg_name(int alg);
/*
* although tree was a legacy algorithm, it has been buggy, so
* exclude it.
*/
#define CRUSH_LEGACY_ALLOWED_BUCKET_ALGS ( \
(1 << CRUSH_BUCKET_UNIFORM) | \
(1 << CRUSH_BUCKET_LIST) | \
(1 << CRUSH_BUCKET_STRAW))
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;
};
/** @ingroup API
*
* Replacement weights for each item in a bucket. The size of the
* array must be exactly the size of the straw2 bucket, just as the
* item_weights array.
*
*/
struct crush_weight_set {
__u32 *weights; /*!< 16.16 fixed point weights
in the same order as items */
__u32 size; /*!< size of the __weights__ array */
};
/** @ingroup API
*
* Replacement weights and ids for a given straw2 bucket, for
* placement purposes.
*
* When crush_do_rule() chooses the Nth item from a straw2 bucket, the
* replacement weights found at __weight_set[N]__ are used instead of
* the weights from __item_weights__. If __N__ is greater than
* __weight_set_size__, the weights found at __weight_set_size-1__ are
* used instead. For instance if __weight_set__ is:
*
* [ [ 0x10000, 0x20000 ], // position 0
* [ 0x20000, 0x40000 ] ] // position 1
*
* choosing the 0th item will use position 0 weights [ 0x10000, 0x20000 ]
* choosing the 1th item will use position 1 weights [ 0x20000, 0x40000 ]
* choosing the 2th item will use position 1 weights [ 0x20000, 0x40000 ]
* etc.
*
*/
struct crush_choose_arg {
__s32 *ids; /*!< values to use instead of items */
__u32 ids_size; /*!< size of the __ids__ array */
struct crush_weight_set *weight_set; /*!< weight replacements for
a given position */
__u32 weight_set_size; /*!< size of the __weight_set__ array */
};
/** @ingroup API
*
* Replacement weights and ids for each bucket in the crushmap. The
* __size__ of the __args__ array must be exactly the same as the
* __map->max_buckets__.
*
* The __crush_choose_arg__ at index N will be used when choosing
* an item from the bucket __map->buckets[N]__ bucket, provided it
* is a straw2 bucket.
*
*/
struct crush_choose_arg_map {
struct crush_choose_arg *args; /*!< replacement for each bucket
in the crushmap */
__u32 size; /*!< size of the __args__ array */
};
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 */
};
struct crush_bucket_straw2 {
struct crush_bucket h;
__u32 *item_weights; /* 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;
/* choose local retries before re-descent */
__u32 choose_local_tries;
/* choose local attempts using a fallback permutation before
* re-descent */
__u32 choose_local_fallback_tries;
/* choose attempts before giving up */
__u32 choose_total_tries;
/* attempt chooseleaf inner descent once for firstn mode; on
* reject retry outer descent. Note that this does *not*
* apply to a collision: in that case we will retry as we used
* to. */
__u32 chooseleaf_descend_once;
/* if non-zero, feed r into chooseleaf, bit-shifted right by (r-1)
* bits. a value of 1 is best for new clusters. for legacy clusters
* that want to limit reshuffling, a value of 3 or 4 will make the
* mappings line up a bit better with previous mappings. */
__u8 chooseleaf_vary_r;
/* if true, it makes chooseleaf firstn to return stable results (if
* no local retry) so that data migrations would be optimal when some
* device fails. */
__u8 chooseleaf_stable;
/*
* This value is calculated after decode or construction by
* the builder. It is exposed here (rather than having a
* 'build CRUSH working space' function) so that callers can
* reserve a static buffer, allocate space on the stack, or
* otherwise avoid calling into the heap allocator if they
* want to. The size of the working space depends on the map,
* while the size of the scratch vector passed to the mapper
* depends on the size of the desired result set.
*
* Nothing stops the caller from allocating both in one swell
* foop and passing in two points, though.
*/
size_t working_size;
#ifndef __KERNEL__
/*
* version 0 (original) of straw_calc has various flaws. version 1
* fixes a few of them.
*/
__u8 straw_calc_version;
/*
* allowed bucket algs is a bitmask, here the bit positions
* are CRUSH_BUCKET_*. note that these are *bits* and
* CRUSH_BUCKET_* values are not, so we need to or together (1
* << CRUSH_BUCKET_WHATEVER). The 0th bit is not used to
* minimize confusion (bucket type values start at 1).
*/
__u32 allowed_bucket_algs;
__u32 *choose_tries;
#endif
};
/* 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_straw2(struct crush_bucket_straw2 *b);
extern void crush_destroy_bucket(struct crush_bucket *b);
extern void crush_destroy_rule(struct crush_rule *r);
extern void crush_destroy(struct crush_map *map);
static inline int crush_calc_tree_node(int i)
{
return ((i+1) << 1)-1;
}
/*
* These data structures are private to the CRUSH implementation. They
* are exposed in this header file because builder needs their
* definitions to calculate the total working size.
*
* Moving this out of the crush map allow us to treat the CRUSH map as
* immutable within the mapper and removes the requirement for a CRUSH
* map lock.
*/
struct crush_work_bucket {
__u32 perm_x; /* @x for which *perm is defined */
__u32 perm_n; /* num elements of *perm that are permuted/defined */
__u32 *perm; /* Permutation of the bucket's items */
};
struct crush_work {
struct crush_work_bucket **work; /* Per-bucket working store */
};
#endif
