#ifndef CEPH_CRUSH_CRUSH_H
#define CEPH_CRUSH_CRUSH_H

#ifdef __KERNEL__
# 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;

        /*
         * cached random permutation: used for uniform bucket and for
         * the linear search fallback for the other bucket types.
         */
        __u32 perm_x;  /* @x for which *perm is defined */
        __u32 perm_n;  /* num elements of *perm that are permuted/defined */
        __u32 *perm;
};

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;

#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;
#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;
}

#endif