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/include/linux/crush/crush.h

https://github.com/airy09/android_kernel_sony_apq8064
C Header | 180 lines | 91 code | 30 blank | 59 comment | 0 complexity | 04ae34241454646192a49933978e7885 MD5 | raw file
  1#ifndef CEPH_CRUSH_CRUSH_H
  2#define CEPH_CRUSH_CRUSH_H
  3
  4#include <linux/types.h>
  5
  6/*
  7 * CRUSH is a pseudo-random data distribution algorithm that
  8 * efficiently distributes input values (typically, data objects)
  9 * across a heterogeneous, structured storage cluster.
 10 *
 11 * The algorithm was originally described in detail in this paper
 12 * (although the algorithm has evolved somewhat since then):
 13 *
 14 *     http://www.ssrc.ucsc.edu/Papers/weil-sc06.pdf
 15 *
 16 * LGPL2
 17 */
 18
 19
 20#define CRUSH_MAGIC 0x00010000ul   /* for detecting algorithm revisions */
 21
 22
 23#define CRUSH_MAX_DEPTH 10  /* max crush hierarchy depth */
 24#define CRUSH_MAX_SET   10  /* max size of a mapping result */
 25
 26
 27/*
 28 * CRUSH uses user-defined "rules" to describe how inputs should be
 29 * mapped to devices.  A rule consists of sequence of steps to perform
 30 * to generate the set of output devices.
 31 */
 32struct crush_rule_step {
 33	__u32 op;
 34	__s32 arg1;
 35	__s32 arg2;
 36};
 37
 38/* step op codes */
 39enum {
 40	CRUSH_RULE_NOOP = 0,
 41	CRUSH_RULE_TAKE = 1,          /* arg1 = value to start with */
 42	CRUSH_RULE_CHOOSE_FIRSTN = 2, /* arg1 = num items to pick */
 43				      /* arg2 = type */
 44	CRUSH_RULE_CHOOSE_INDEP = 3,  /* same */
 45	CRUSH_RULE_EMIT = 4,          /* no args */
 46	CRUSH_RULE_CHOOSE_LEAF_FIRSTN = 6,
 47	CRUSH_RULE_CHOOSE_LEAF_INDEP = 7,
 48};
 49
 50/*
 51 * for specifying choose num (arg1) relative to the max parameter
 52 * passed to do_rule
 53 */
 54#define CRUSH_CHOOSE_N            0
 55#define CRUSH_CHOOSE_N_MINUS(x)   (-(x))
 56
 57/*
 58 * The rule mask is used to describe what the rule is intended for.
 59 * Given a ruleset and size of output set, we search through the
 60 * rule list for a matching rule_mask.
 61 */
 62struct crush_rule_mask {
 63	__u8 ruleset;
 64	__u8 type;
 65	__u8 min_size;
 66	__u8 max_size;
 67};
 68
 69struct crush_rule {
 70	__u32 len;
 71	struct crush_rule_mask mask;
 72	struct crush_rule_step steps[0];
 73};
 74
 75#define crush_rule_size(len) (sizeof(struct crush_rule) + \
 76			      (len)*sizeof(struct crush_rule_step))
 77
 78
 79
 80/*
 81 * A bucket is a named container of other items (either devices or
 82 * other buckets).  Items within a bucket are chosen using one of a
 83 * few different algorithms.  The table summarizes how the speed of
 84 * each option measures up against mapping stability when items are
 85 * added or removed.
 86 *
 87 *  Bucket Alg     Speed       Additions    Removals
 88 *  ------------------------------------------------
 89 *  uniform         O(1)       poor         poor
 90 *  list            O(n)       optimal      poor
 91 *  tree            O(log n)   good         good
 92 *  straw           O(n)       optimal      optimal
 93 */
 94enum {
 95	CRUSH_BUCKET_UNIFORM = 1,
 96	CRUSH_BUCKET_LIST = 2,
 97	CRUSH_BUCKET_TREE = 3,
 98	CRUSH_BUCKET_STRAW = 4
 99};
100extern const char *crush_bucket_alg_name(int alg);
101
102struct crush_bucket {
103	__s32 id;        /* this'll be negative */
104	__u16 type;      /* non-zero; type=0 is reserved for devices */
105	__u8 alg;        /* one of CRUSH_BUCKET_* */
106	__u8 hash;       /* which hash function to use, CRUSH_HASH_* */
107	__u32 weight;    /* 16-bit fixed point */
108	__u32 size;      /* num items */
109	__s32 *items;
110
111	/*
112	 * cached random permutation: used for uniform bucket and for
113	 * the linear search fallback for the other bucket types.
114	 */
115	__u32 perm_x;  /* @x for which *perm is defined */
116	__u32 perm_n;  /* num elements of *perm that are permuted/defined */
117	__u32 *perm;
118};
119
120struct crush_bucket_uniform {
121	struct crush_bucket h;
122	__u32 item_weight;  /* 16-bit fixed point; all items equally weighted */
123};
124
125struct crush_bucket_list {
126	struct crush_bucket h;
127	__u32 *item_weights;  /* 16-bit fixed point */
128	__u32 *sum_weights;   /* 16-bit fixed point.  element i is sum
129				 of weights 0..i, inclusive */
130};
131
132struct crush_bucket_tree {
133	struct crush_bucket h;  /* note: h.size is _tree_ size, not number of
134				   actual items */
135	__u8 num_nodes;
136	__u32 *node_weights;
137};
138
139struct crush_bucket_straw {
140	struct crush_bucket h;
141	__u32 *item_weights;   /* 16-bit fixed point */
142	__u32 *straws;         /* 16-bit fixed point */
143};
144
145
146
147/*
148 * CRUSH map includes all buckets, rules, etc.
149 */
150struct crush_map {
151	struct crush_bucket **buckets;
152	struct crush_rule **rules;
153
154	/*
155	 * Parent pointers to identify the parent bucket a device or
156	 * bucket in the hierarchy.  If an item appears more than
157	 * once, this is the _last_ time it appeared (where buckets
158	 * are processed in bucket id order, from -1 on down to
159	 * -max_buckets.
160	 */
161	__u32 *bucket_parents;
162	__u32 *device_parents;
163
164	__s32 max_buckets;
165	__u32 max_rules;
166	__s32 max_devices;
167};
168
169
170/* crush.c */
171extern int crush_get_bucket_item_weight(struct crush_bucket *b, int pos);
172extern void crush_calc_parents(struct crush_map *map);
173extern void crush_destroy_bucket_uniform(struct crush_bucket_uniform *b);
174extern void crush_destroy_bucket_list(struct crush_bucket_list *b);
175extern void crush_destroy_bucket_tree(struct crush_bucket_tree *b);
176extern void crush_destroy_bucket_straw(struct crush_bucket_straw *b);
177extern void crush_destroy_bucket(struct crush_bucket *b);
178extern void crush_destroy(struct crush_map *map);
179
180#endif