include/linux/crush/crush.h

   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  *     http://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[0];
  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         /* CrushWrapper::choose_args */
 305         struct rb_root choose_args;
 306 #endif
 307 };
 308
 309
 310 /* crush.c */
 311 extern int crush_get_bucket_item_weight(const struct crush_bucket *b, int pos);
 312 extern void crush_destroy_bucket_uniform(struct crush_bucket_uniform *b);
 313 extern void crush_destroy_bucket_list(struct crush_bucket_list *b);
 314 extern void crush_destroy_bucket_tree(struct crush_bucket_tree *b);
 315 extern void crush_destroy_bucket_straw(struct crush_bucket_straw *b);
 316 extern void crush_destroy_bucket_straw2(struct crush_bucket_straw2 *b);
 317 extern void crush_destroy_bucket(struct crush_bucket *b);
 318 extern void crush_destroy_rule(struct crush_rule *r);
 319 extern void crush_destroy(struct crush_map *map);
 320
 321 static inline int crush_calc_tree_node(int i)
 322 {
 323         return ((i+1) << 1)-1;
 324 }
 325
 326 /*
 327  * These data structures are private to the CRUSH implementation. They
 328  * are exposed in this header file because builder needs their
 329  * definitions to calculate the total working size.
 330  *
 331  * Moving this out of the crush map allow us to treat the CRUSH map as
 332  * immutable within the mapper and removes the requirement for a CRUSH
 333  * map lock.
 334  */
 335 struct crush_work_bucket {
 336         __u32 perm_x; /* @x for which *perm is defined */
 337         __u32 perm_n; /* num elements of *perm that are permuted/defined */
 338         __u32 *perm;  /* Permutation of the bucket's items */
 339 };
 340
 341 struct crush_work {
 342         struct crush_work_bucket **work; /* Per-bucket working store */
 343 };
 344
 345 #endif