Edit File: crush.h
#ifndef CEPH_CRUSH_CRUSH_H #define CEPH_CRUSH_CRUSH_H #ifdef __KERNEL__ # include <linux/rbtree.h> # 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 { #ifdef __KERNEL__ struct rb_node node; s64 choose_args_index; #endif 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; #else /* CrushWrapper::choose_args */ struct rb_root choose_args; #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