1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef CEPH_CRUSH_CRUSH_H 3 #define CEPH_CRUSH_CRUSH_H 4 5 #ifdef __KERNEL__ 6 # include <linux/rbtree.h> 7 # include <linux/types.h> 8 #else 9 # include "crush_compat.h" 10 #endif 11 12 /* 13 * CRUSH is a pseudo-random data distribution algorithm that 14 * efficiently distributes input values (typically, data objects) 15 * across a heterogeneous, structured storage cluster. 16 * 17 * The algorithm was originally described in detail in this paper 18 * (although the algorithm has evolved somewhat since then): 19 * 20 * https://www.ssrc.ucsc.edu/Papers/weil-sc06.pdf 21 * 22 * LGPL2 23 */ 24 25 26 #define CRUSH_MAGIC 0x00010000ul /* for detecting algorithm revisions */ 27 28 #define CRUSH_MAX_DEPTH 10 /* max crush hierarchy depth */ 29 #define CRUSH_MAX_RULESET (1<<8) /* max crush ruleset number */ 30 #define CRUSH_MAX_RULES CRUSH_MAX_RULESET /* should be the same as max rulesets */ 31 32 #define CRUSH_MAX_DEVICE_WEIGHT (100u * 0x10000u) 33 #define CRUSH_MAX_BUCKET_WEIGHT (65535u * 0x10000u) 34 35 #define CRUSH_ITEM_UNDEF 0x7ffffffe /* undefined result (internal use only) */ 36 #define CRUSH_ITEM_NONE 0x7fffffff /* no result */ 37 38 /* 39 * CRUSH uses user-defined "rules" to describe how inputs should be 40 * mapped to devices. A rule consists of sequence of steps to perform 41 * to generate the set of output devices. 42 */ 43 struct crush_rule_step { 44 __u32 op; 45 __s32 arg1; 46 __s32 arg2; 47 }; 48 49 /* step op codes */ 50 enum { 51 CRUSH_RULE_NOOP = 0, 52 CRUSH_RULE_TAKE = 1, /* arg1 = value to start with */ 53 CRUSH_RULE_CHOOSE_FIRSTN = 2, /* arg1 = num items to pick */ 54 /* arg2 = type */ 55 CRUSH_RULE_CHOOSE_INDEP = 3, /* same */ 56 CRUSH_RULE_EMIT = 4, /* no args */ 57 CRUSH_RULE_CHOOSELEAF_FIRSTN = 6, 58 CRUSH_RULE_CHOOSELEAF_INDEP = 7, 59 60 CRUSH_RULE_SET_CHOOSE_TRIES = 8, /* override choose_total_tries */ 61 CRUSH_RULE_SET_CHOOSELEAF_TRIES = 9, /* override chooseleaf_descend_once */ 62 CRUSH_RULE_SET_CHOOSE_LOCAL_TRIES = 10, 63 CRUSH_RULE_SET_CHOOSE_LOCAL_FALLBACK_TRIES = 11, 64 CRUSH_RULE_SET_CHOOSELEAF_VARY_R = 12, 65 CRUSH_RULE_SET_CHOOSELEAF_STABLE = 13 66 }; 67 68 /* 69 * for specifying choose num (arg1) relative to the max parameter 70 * passed to do_rule 71 */ 72 #define CRUSH_CHOOSE_N 0 73 #define CRUSH_CHOOSE_N_MINUS(x) (-(x)) 74 75 /* 76 * The rule mask is used to describe what the rule is intended for. 77 * Given a ruleset and size of output set, we search through the 78 * rule list for a matching rule_mask. 79 */ 80 struct crush_rule_mask { 81 __u8 ruleset; 82 __u8 type; 83 __u8 min_size; 84 __u8 max_size; 85 }; 86 87 struct crush_rule { 88 __u32 len; 89 struct crush_rule_mask mask; 90 struct crush_rule_step steps[]; 91 }; 92 93 #define crush_rule_size(len) (sizeof(struct crush_rule) + \ 94 (len)*sizeof(struct crush_rule_step)) 95 96 97 98 /* 99 * A bucket is a named container of other items (either devices or 100 * other buckets). Items within a bucket are chosen using one of a 101 * few different algorithms. The table summarizes how the speed of 102 * each option measures up against mapping stability when items are 103 * added or removed. 104 * 105 * Bucket Alg Speed Additions Removals 106 * ------------------------------------------------ 107 * uniform O(1) poor poor 108 * list O(n) optimal poor 109 * tree O(log n) good good 110 * straw O(n) better better 111 * straw2 O(n) optimal optimal 112 */ 113 enum { 114 CRUSH_BUCKET_UNIFORM = 1, 115 CRUSH_BUCKET_LIST = 2, 116 CRUSH_BUCKET_TREE = 3, 117 CRUSH_BUCKET_STRAW = 4, 118 CRUSH_BUCKET_STRAW2 = 5, 119 }; 120 extern const char *crush_bucket_alg_name(int alg); 121 122 /* 123 * although tree was a legacy algorithm, it has been buggy, so 124 * exclude it. 125 */ 126 #define CRUSH_LEGACY_ALLOWED_BUCKET_ALGS ( \ 127 (1 << CRUSH_BUCKET_UNIFORM) | \ 128 (1 << CRUSH_BUCKET_LIST) | \ 129 (1 << CRUSH_BUCKET_STRAW)) 130 131 struct crush_bucket { 132 __s32 id; /* this'll be negative */ 133 __u16 type; /* non-zero; type=0 is reserved for devices */ 134 __u8 alg; /* one of CRUSH_BUCKET_* */ 135 __u8 hash; /* which hash function to use, CRUSH_HASH_* */ 136 __u32 weight; /* 16-bit fixed point */ 137 __u32 size; /* num items */ 138 __s32 *items; 139 140 }; 141 142 /** @ingroup API 143 * 144 * Replacement weights for each item in a bucket. The size of the 145 * array must be exactly the size of the straw2 bucket, just as the 146 * item_weights array. 147 * 148 */ 149 struct crush_weight_set { 150 __u32 *weights; /*!< 16.16 fixed point weights 151 in the same order as items */ 152 __u32 size; /*!< size of the __weights__ array */ 153 }; 154 155 /** @ingroup API 156 * 157 * Replacement weights and ids for a given straw2 bucket, for 158 * placement purposes. 159 * 160 * When crush_do_rule() chooses the Nth item from a straw2 bucket, the 161 * replacement weights found at __weight_set[N]__ are used instead of 162 * the weights from __item_weights__. If __N__ is greater than 163 * __weight_set_size__, the weights found at __weight_set_size-1__ are 164 * used instead. For instance if __weight_set__ is: 165 * 166 * [ [ 0x10000, 0x20000 ], // position 0 167 * [ 0x20000, 0x40000 ] ] // position 1 168 * 169 * choosing the 0th item will use position 0 weights [ 0x10000, 0x20000 ] 170 * choosing the 1th item will use position 1 weights [ 0x20000, 0x40000 ] 171 * choosing the 2th item will use position 1 weights [ 0x20000, 0x40000 ] 172 * etc. 173 * 174 */ 175 struct crush_choose_arg { 176 __s32 *ids; /*!< values to use instead of items */ 177 __u32 ids_size; /*!< size of the __ids__ array */ 178 struct crush_weight_set *weight_set; /*!< weight replacements for 179 a given position */ 180 __u32 weight_set_size; /*!< size of the __weight_set__ array */ 181 }; 182 183 /** @ingroup API 184 * 185 * Replacement weights and ids for each bucket in the crushmap. The 186 * __size__ of the __args__ array must be exactly the same as the 187 * __map->max_buckets__. 188 * 189 * The __crush_choose_arg__ at index N will be used when choosing 190 * an item from the bucket __map->buckets[N]__ bucket, provided it 191 * is a straw2 bucket. 192 * 193 */ 194 struct crush_choose_arg_map { 195 #ifdef __KERNEL__ 196 struct rb_node node; 197 s64 choose_args_index; 198 #endif 199 struct crush_choose_arg *args; /*!< replacement for each bucket 200 in the crushmap */ 201 __u32 size; /*!< size of the __args__ array */ 202 }; 203 204 struct crush_bucket_uniform { 205 struct crush_bucket h; 206 __u32 item_weight; /* 16-bit fixed point; all items equally weighted */ 207 }; 208 209 struct crush_bucket_list { 210 struct crush_bucket h; 211 __u32 *item_weights; /* 16-bit fixed point */ 212 __u32 *sum_weights; /* 16-bit fixed point. element i is sum 213 of weights 0..i, inclusive */ 214 }; 215 216 struct crush_bucket_tree { 217 struct crush_bucket h; /* note: h.size is _tree_ size, not number of 218 actual items */ 219 __u8 num_nodes; 220 __u32 *node_weights; 221 }; 222 223 struct crush_bucket_straw { 224 struct crush_bucket h; 225 __u32 *item_weights; /* 16-bit fixed point */ 226 __u32 *straws; /* 16-bit fixed point */ 227 }; 228 229 struct crush_bucket_straw2 { 230 struct crush_bucket h; 231 __u32 *item_weights; /* 16-bit fixed point */ 232 }; 233 234 235 236 /* 237 * CRUSH map includes all buckets, rules, etc. 238 */ 239 struct crush_map { 240 struct crush_bucket **buckets; 241 struct crush_rule **rules; 242 243 __s32 max_buckets; 244 __u32 max_rules; 245 __s32 max_devices; 246 247 /* choose local retries before re-descent */ 248 __u32 choose_local_tries; 249 /* choose local attempts using a fallback permutation before 250 * re-descent */ 251 __u32 choose_local_fallback_tries; 252 /* choose attempts before giving up */ 253 __u32 choose_total_tries; 254 /* attempt chooseleaf inner descent once for firstn mode; on 255 * reject retry outer descent. Note that this does *not* 256 * apply to a collision: in that case we will retry as we used 257 * to. */ 258 __u32 chooseleaf_descend_once; 259 260 /* if non-zero, feed r into chooseleaf, bit-shifted right by (r-1) 261 * bits. a value of 1 is best for new clusters. for legacy clusters 262 * that want to limit reshuffling, a value of 3 or 4 will make the 263 * mappings line up a bit better with previous mappings. */ 264 __u8 chooseleaf_vary_r; 265 266 /* if true, it makes chooseleaf firstn to return stable results (if 267 * no local retry) so that data migrations would be optimal when some 268 * device fails. */ 269 __u8 chooseleaf_stable; 270 271 /* 272 * This value is calculated after decode or construction by 273 * the builder. It is exposed here (rather than having a 274 * 'build CRUSH working space' function) so that callers can 275 * reserve a static buffer, allocate space on the stack, or 276 * otherwise avoid calling into the heap allocator if they 277 * want to. The size of the working space depends on the map, 278 * while the size of the scratch vector passed to the mapper 279 * depends on the size of the desired result set. 280 * 281 * Nothing stops the caller from allocating both in one swell 282 * foop and passing in two points, though. 283 */ 284 size_t working_size; 285 286 #ifndef __KERNEL__ 287 /* 288 * version 0 (original) of straw_calc has various flaws. version 1 289 * fixes a few of them. 290 */ 291 __u8 straw_calc_version; 292 293 /* 294 * allowed bucket algs is a bitmask, here the bit positions 295 * are CRUSH_BUCKET_*. note that these are *bits* and 296 * CRUSH_BUCKET_* values are not, so we need to or together (1 297 * << CRUSH_BUCKET_WHATEVER). The 0th bit is not used to 298 * minimize confusion (bucket type values start at 1). 299 */ 300 __u32 allowed_bucket_algs; 301 302 __u32 *choose_tries; 303 #else 304 /* device/bucket type id -> type name (CrushWrapper::type_map) */ 305 struct rb_root type_names; 306 307 /* device/bucket id -> name (CrushWrapper::name_map) */ 308 struct rb_root names; 309 310 /* CrushWrapper::choose_args */ 311 struct rb_root choose_args; 312 #endif 313 }; 314 315 316 /* crush.c */ 317 extern int crush_get_bucket_item_weight(const struct crush_bucket *b, int pos); 318 extern void crush_destroy_bucket_uniform(struct crush_bucket_uniform *b); 319 extern void crush_destroy_bucket_list(struct crush_bucket_list *b); 320 extern void crush_destroy_bucket_tree(struct crush_bucket_tree *b); 321 extern void crush_destroy_bucket_straw(struct crush_bucket_straw *b); 322 extern void crush_destroy_bucket_straw2(struct crush_bucket_straw2 *b); 323 extern void crush_destroy_bucket(struct crush_bucket *b); 324 extern void crush_destroy_rule(struct crush_rule *r); 325 extern void crush_destroy(struct crush_map *map); 326 crush_calc_tree_node(int i)327 static inline int crush_calc_tree_node(int i) 328 { 329 return ((i+1) << 1)-1; 330 } 331 332 /* 333 * These data structures are private to the CRUSH implementation. They 334 * are exposed in this header file because builder needs their 335 * definitions to calculate the total working size. 336 * 337 * Moving this out of the crush map allow us to treat the CRUSH map as 338 * immutable within the mapper and removes the requirement for a CRUSH 339 * map lock. 340 */ 341 struct crush_work_bucket { 342 __u32 perm_x; /* @x for which *perm is defined */ 343 __u32 perm_n; /* num elements of *perm that are permuted/defined */ 344 __u32 *perm; /* Permutation of the bucket's items */ 345 }; 346 347 struct crush_work { 348 struct crush_work_bucket **work; /* Per-bucket working store */ 349 #ifdef __KERNEL__ 350 struct list_head item; 351 #endif 352 }; 353 354 #ifdef __KERNEL__ 355 /* osdmap.c */ 356 void clear_crush_names(struct rb_root *root); 357 void clear_choose_args(struct crush_map *c); 358 #endif 359 360 #endif 361