246 lines
7.0 KiB
C
246 lines
7.0 KiB
C
#ifndef CEPH_CRUSH_CRUSH_H
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#define CEPH_CRUSH_CRUSH_H
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#ifdef __KERNEL__
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# include <linux/types.h>
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#else
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# include "crush_compat.h"
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#endif
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/*
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* CRUSH is a pseudo-random data distribution algorithm that
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* efficiently distributes input values (typically, data objects)
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* across a heterogeneous, structured storage cluster.
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*
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* The algorithm was originally described in detail in this paper
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* (although the algorithm has evolved somewhat since then):
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*
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* http://www.ssrc.ucsc.edu/Papers/weil-sc06.pdf
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*
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* LGPL2
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*/
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#define CRUSH_MAGIC 0x00010000ul /* for detecting algorithm revisions */
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#define CRUSH_MAX_DEPTH 10 /* max crush hierarchy depth */
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#define CRUSH_MAX_RULESET (1<<8) /* max crush ruleset number */
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#define CRUSH_MAX_RULES CRUSH_MAX_RULESET /* should be the same as max rulesets */
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#define CRUSH_MAX_DEVICE_WEIGHT (100u * 0x10000u)
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#define CRUSH_MAX_BUCKET_WEIGHT (65535u * 0x10000u)
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#define CRUSH_ITEM_UNDEF 0x7ffffffe /* undefined result (internal use only) */
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#define CRUSH_ITEM_NONE 0x7fffffff /* no result */
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/*
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* CRUSH uses user-defined "rules" to describe how inputs should be
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* mapped to devices. A rule consists of sequence of steps to perform
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* to generate the set of output devices.
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*/
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struct crush_rule_step {
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__u32 op;
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__s32 arg1;
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__s32 arg2;
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};
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/* step op codes */
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enum {
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CRUSH_RULE_NOOP = 0,
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CRUSH_RULE_TAKE = 1, /* arg1 = value to start with */
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CRUSH_RULE_CHOOSE_FIRSTN = 2, /* arg1 = num items to pick */
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/* arg2 = type */
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CRUSH_RULE_CHOOSE_INDEP = 3, /* same */
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CRUSH_RULE_EMIT = 4, /* no args */
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CRUSH_RULE_CHOOSELEAF_FIRSTN = 6,
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CRUSH_RULE_CHOOSELEAF_INDEP = 7,
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CRUSH_RULE_SET_CHOOSE_TRIES = 8, /* override choose_total_tries */
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CRUSH_RULE_SET_CHOOSELEAF_TRIES = 9, /* override chooseleaf_descend_once */
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CRUSH_RULE_SET_CHOOSE_LOCAL_TRIES = 10,
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CRUSH_RULE_SET_CHOOSE_LOCAL_FALLBACK_TRIES = 11,
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CRUSH_RULE_SET_CHOOSELEAF_VARY_R = 12
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};
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/*
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* for specifying choose num (arg1) relative to the max parameter
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* passed to do_rule
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*/
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#define CRUSH_CHOOSE_N 0
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#define CRUSH_CHOOSE_N_MINUS(x) (-(x))
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/*
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* The rule mask is used to describe what the rule is intended for.
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* Given a ruleset and size of output set, we search through the
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* rule list for a matching rule_mask.
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*/
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struct crush_rule_mask {
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__u8 ruleset;
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__u8 type;
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__u8 min_size;
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__u8 max_size;
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};
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struct crush_rule {
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__u32 len;
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struct crush_rule_mask mask;
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struct crush_rule_step steps[0];
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};
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#define crush_rule_size(len) (sizeof(struct crush_rule) + \
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(len)*sizeof(struct crush_rule_step))
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/*
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* A bucket is a named container of other items (either devices or
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* other buckets). Items within a bucket are chosen using one of a
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* few different algorithms. The table summarizes how the speed of
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* each option measures up against mapping stability when items are
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* added or removed.
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*
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* Bucket Alg Speed Additions Removals
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* ------------------------------------------------
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* uniform O(1) poor poor
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* list O(n) optimal poor
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* tree O(log n) good good
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* straw O(n) better better
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* straw2 O(n) optimal optimal
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*/
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enum {
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CRUSH_BUCKET_UNIFORM = 1,
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CRUSH_BUCKET_LIST = 2,
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CRUSH_BUCKET_TREE = 3,
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CRUSH_BUCKET_STRAW = 4,
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CRUSH_BUCKET_STRAW2 = 5,
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};
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extern const char *crush_bucket_alg_name(int alg);
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/*
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* although tree was a legacy algorithm, it has been buggy, so
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* exclude it.
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*/
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#define CRUSH_LEGACY_ALLOWED_BUCKET_ALGS ( \
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(1 << CRUSH_BUCKET_UNIFORM) | \
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(1 << CRUSH_BUCKET_LIST) | \
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(1 << CRUSH_BUCKET_STRAW))
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struct crush_bucket {
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__s32 id; /* this'll be negative */
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__u16 type; /* non-zero; type=0 is reserved for devices */
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__u8 alg; /* one of CRUSH_BUCKET_* */
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__u8 hash; /* which hash function to use, CRUSH_HASH_* */
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__u32 weight; /* 16-bit fixed point */
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__u32 size; /* num items */
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__s32 *items;
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/*
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* cached random permutation: used for uniform bucket and for
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* the linear search fallback for the other bucket types.
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*/
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__u32 perm_x; /* @x for which *perm is defined */
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__u32 perm_n; /* num elements of *perm that are permuted/defined */
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__u32 *perm;
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};
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struct crush_bucket_uniform {
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struct crush_bucket h;
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__u32 item_weight; /* 16-bit fixed point; all items equally weighted */
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};
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struct crush_bucket_list {
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struct crush_bucket h;
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__u32 *item_weights; /* 16-bit fixed point */
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__u32 *sum_weights; /* 16-bit fixed point. element i is sum
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of weights 0..i, inclusive */
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};
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struct crush_bucket_tree {
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struct crush_bucket h; /* note: h.size is _tree_ size, not number of
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actual items */
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__u8 num_nodes;
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__u32 *node_weights;
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};
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struct crush_bucket_straw {
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struct crush_bucket h;
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__u32 *item_weights; /* 16-bit fixed point */
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__u32 *straws; /* 16-bit fixed point */
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};
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struct crush_bucket_straw2 {
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struct crush_bucket h;
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__u32 *item_weights; /* 16-bit fixed point */
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};
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/*
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* CRUSH map includes all buckets, rules, etc.
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*/
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struct crush_map {
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struct crush_bucket **buckets;
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struct crush_rule **rules;
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__s32 max_buckets;
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__u32 max_rules;
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__s32 max_devices;
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/* choose local retries before re-descent */
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__u32 choose_local_tries;
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/* choose local attempts using a fallback permutation before
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* re-descent */
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__u32 choose_local_fallback_tries;
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/* choose attempts before giving up */
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__u32 choose_total_tries;
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/* attempt chooseleaf inner descent once for firstn mode; on
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* reject retry outer descent. Note that this does *not*
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* apply to a collision: in that case we will retry as we used
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* to. */
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__u32 chooseleaf_descend_once;
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/* if non-zero, feed r into chooseleaf, bit-shifted right by (r-1)
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* bits. a value of 1 is best for new clusters. for legacy clusters
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* that want to limit reshuffling, a value of 3 or 4 will make the
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* mappings line up a bit better with previous mappings. */
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__u8 chooseleaf_vary_r;
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#ifndef __KERNEL__
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/*
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* version 0 (original) of straw_calc has various flaws. version 1
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* fixes a few of them.
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*/
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__u8 straw_calc_version;
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/*
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* allowed bucket algs is a bitmask, here the bit positions
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* are CRUSH_BUCKET_*. note that these are *bits* and
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* CRUSH_BUCKET_* values are not, so we need to or together (1
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* << CRUSH_BUCKET_WHATEVER). The 0th bit is not used to
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* minimize confusion (bucket type values start at 1).
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*/
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__u32 allowed_bucket_algs;
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__u32 *choose_tries;
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#endif
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};
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/* crush.c */
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extern int crush_get_bucket_item_weight(const struct crush_bucket *b, int pos);
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extern void crush_destroy_bucket_uniform(struct crush_bucket_uniform *b);
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extern void crush_destroy_bucket_list(struct crush_bucket_list *b);
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extern void crush_destroy_bucket_tree(struct crush_bucket_tree *b);
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extern void crush_destroy_bucket_straw(struct crush_bucket_straw *b);
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extern void crush_destroy_bucket_straw2(struct crush_bucket_straw2 *b);
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extern void crush_destroy_bucket(struct crush_bucket *b);
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extern void crush_destroy_rule(struct crush_rule *r);
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extern void crush_destroy(struct crush_map *map);
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static inline int crush_calc_tree_node(int i)
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{
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return ((i+1) << 1)-1;
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}
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#endif
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