staging: iio: Documentation fixes

[zen-stable.git] / fs / ceph / crush / mapper.c

#ifdef __KERNEL__
# include <linux/string.h>
# include <linux/slab.h>
# include <linux/bug.h>
# include <linux/kernel.h>
# ifndef dprintk
#  define dprintk(args...)
# endif
#else
# include <string.h>
# include <stdio.h>
# include <stdlib.h>
# include <assert.h>
# define BUG_ON(x) assert(!(x))
# define dprintk(args...) /* printf(args) */
# define kmalloc(x, f) malloc(x)
# define kfree(x) free(x)
#endif

#include "crush.h"
#include "hash.h"

/*
 * Implement the core CRUSH mapping algorithm.
 */

/**
 * crush_find_rule - find a crush_rule id for a given ruleset, type, and size.
 * @map: the crush_map
 * @ruleset: the storage ruleset id (user defined)
 * @type: storage ruleset type (user defined)
 * @size: output set size
 */
int crush_find_rule(struct crush_map *map, int ruleset, int type, int size)
{
        int i;

        for (i = 0; i < map->max_rules; i++) {
                if (map->rules[i] &&
                    map->rules[i]->mask.ruleset == ruleset &&
                    map->rules[i]->mask.type == type &&
                    map->rules[i]->mask.min_size <= size &&
                    map->rules[i]->mask.max_size >= size)
                        return i;
        }
        return -1;
}


/*
 * bucket choose methods
 *
 * For each bucket algorithm, we have a "choose" method that, given a
 * crush input @x and replica position (usually, position in output set) @r,
 * will produce an item in the bucket.
 */

/*
 * Choose based on a random permutation of the bucket.
 *
 * We used to use some prime number arithmetic to do this, but it
 * wasn't very random, and had some other bad behaviors.  Instead, we
 * calculate an actual random permutation of the bucket members.
 * Since this is expensive, we optimize for the r=0 case, which
 * captures the vast majority of calls.
 */
static int bucket_perm_choose(struct crush_bucket *bucket,
                              int x, int r)
{
        unsigned pr = r % bucket->size;
        unsigned i, s;

        /* start a new permutation if @x has changed */
        if (bucket->perm_x != x || bucket->perm_n == 0) {
                dprintk("bucket %d new x=%d\n", bucket->id, x);
                bucket->perm_x = x;

                /* optimize common r=0 case */
                if (pr == 0) {
                        s = crush_hash32_3(bucket->hash, x, bucket->id, 0) %
                                bucket->size;
                        bucket->perm[0] = s;
                        bucket->perm_n = 0xffff;   /* magic value, see below */
                        goto out;
                }

                for (i = 0; i < bucket->size; i++)
                        bucket->perm[i] = i;
                bucket->perm_n = 0;
        } else if (bucket->perm_n == 0xffff) {
                /* clean up after the r=0 case above */
                for (i = 1; i < bucket->size; i++)
                        bucket->perm[i] = i;
                bucket->perm[bucket->perm[0]] = 0;
                bucket->perm_n = 1;
        }

        /* calculate permutation up to pr */
        for (i = 0; i < bucket->perm_n; i++)
                dprintk(" perm_choose have %d: %d\n", i, bucket->perm[i]);
        while (bucket->perm_n <= pr) {
                unsigned p = bucket->perm_n;
                /* no point in swapping the final entry */
                if (p < bucket->size - 1) {
                        i = crush_hash32_3(bucket->hash, x, bucket->id, p) %
                                (bucket->size - p);
                        if (i) {
                                unsigned t = bucket->perm[p + i];
                                bucket->perm[p + i] = bucket->perm[p];
                                bucket->perm[p] = t;
                        }
                        dprintk(" perm_choose swap %d with %d\n", p, p+i);
                }
                bucket->perm_n++;
        }
        for (i = 0; i < bucket->size; i++)
                dprintk(" perm_choose  %d: %d\n", i, bucket->perm[i]);

        s = bucket->perm[pr];
out:
        dprintk(" perm_choose %d sz=%d x=%d r=%d (%d) s=%d\n", bucket->id,
                bucket->size, x, r, pr, s);
        return bucket->items[s];
}

/* uniform */
static int bucket_uniform_choose(struct crush_bucket_uniform *bucket,
                                 int x, int r)
{
        return bucket_perm_choose(&bucket->h, x, r);
}

/* list */
static int bucket_list_choose(struct crush_bucket_list *bucket,
                              int x, int r)
{
        int i;

        for (i = bucket->h.size-1; i >= 0; i--) {
                __u64 w = crush_hash32_4(bucket->h.hash,x, bucket->h.items[i],
                                         r, bucket->h.id);
                w &= 0xffff;
                dprintk("list_choose i=%d x=%d r=%d item %d weight %x "
                        "sw %x rand %llx",
                        i, x, r, bucket->h.items[i], bucket->item_weights[i],
                        bucket->sum_weights[i], w);
                w *= bucket->sum_weights[i];
                w = w >> 16;
                /*dprintk(" scaled %llx\n", w);*/
                if (w < bucket->item_weights[i])
                        return bucket->h.items[i];
        }

        BUG_ON(1);
        return 0;
}


/* (binary) tree */
static int height(int n)
{
        int h = 0;
        while ((n & 1) == 0) {
                h++;
                n = n >> 1;
        }
        return h;
}

static int left(int x)
{
        int h = height(x);
        return x - (1 << (h-1));
}

static int right(int x)
{
        int h = height(x);
        return x + (1 << (h-1));
}

static int terminal(int x)
{
        return x & 1;
}

static int bucket_tree_choose(struct crush_bucket_tree *bucket,
                              int x, int r)
{
        int n, l;
        __u32 w;
        __u64 t;

        /* start at root */
        n = bucket->num_nodes >> 1;

        while (!terminal(n)) {
                /* pick point in [0, w) */
                w = bucket->node_weights[n];
                t = (__u64)crush_hash32_4(bucket->h.hash, x, n, r,
                                          bucket->h.id) * (__u64)w;
                t = t >> 32;

                /* descend to the left or right? */
                l = left(n);
                if (t < bucket->node_weights[l])
                        n = l;
                else
                        n = right(n);
        }

        return bucket->h.items[n >> 1];
}


/* straw */

static int bucket_straw_choose(struct crush_bucket_straw *bucket,
                               int x, int r)
{
        int i;
        int high = 0;
        __u64 high_draw = 0;
        __u64 draw;

        for (i = 0; i < bucket->h.size; i++) {
                draw = crush_hash32_3(bucket->h.hash, x, bucket->h.items[i], r);
                draw &= 0xffff;
                draw *= bucket->straws[i];
                if (i == 0 || draw > high_draw) {
                        high = i;
                        high_draw = draw;
                }
        }
        return bucket->h.items[high];
}

static int crush_bucket_choose(struct crush_bucket *in, int x, int r)
{
        dprintk("choose %d x=%d r=%d\n", in->id, x, r);
        switch (in->alg) {
        case CRUSH_BUCKET_UNIFORM:
                return bucket_uniform_choose((struct crush_bucket_uniform *)in,
                                          x, r);
        case CRUSH_BUCKET_LIST:
                return bucket_list_choose((struct crush_bucket_list *)in,
                                          x, r);
        case CRUSH_BUCKET_TREE:
                return bucket_tree_choose((struct crush_bucket_tree *)in,
                                          x, r);
        case CRUSH_BUCKET_STRAW:
                return bucket_straw_choose((struct crush_bucket_straw *)in,
                                           x, r);
        default:
                BUG_ON(1);
                return in->items[0];
        }
}

/*
 * true if device is marked "out" (failed, fully offloaded)
 * of the cluster
 */
static int is_out(struct crush_map *map, __u32 *weight, int item, int x)
{
        if (weight[item] >= 0x1000)
                return 0;
        if (weight[item] == 0)
                return 1;
        if ((crush_hash32_2(CRUSH_HASH_RJENKINS1, x, item) & 0xffff)
            < weight[item])
                return 0;
        return 1;
}

/**
 * crush_choose - choose numrep distinct items of given type
 * @map: the crush_map
 * @bucket: the bucket we are choose an item from
 * @x: crush input value
 * @numrep: the number of items to choose
 * @type: the type of item to choose
 * @out: pointer to output vector
 * @outpos: our position in that vector
 * @firstn: true if choosing "first n" items, false if choosing "indep"
 * @recurse_to_leaf: true if we want one device under each item of given type
 * @out2: second output vector for leaf items (if @recurse_to_leaf)
 */
static int crush_choose(struct crush_map *map,
                        struct crush_bucket *bucket,
                        __u32 *weight,
                        int x, int numrep, int type,
                        int *out, int outpos,
                        int firstn, int recurse_to_leaf,
                        int *out2)
{
        int rep;
        int ftotal, flocal;
        int retry_descent, retry_bucket, skip_rep;
        struct crush_bucket *in = bucket;
        int r;
        int i;
        int item = 0;
        int itemtype;
        int collide, reject;
        const int orig_tries = 5; /* attempts before we fall back to search */
        dprintk("choose bucket %d x %d outpos %d\n", bucket->id, x, outpos);

        for (rep = outpos; rep < numrep; rep++) {
                /* keep trying until we get a non-out, non-colliding item */
                ftotal = 0;
                skip_rep = 0;
                do {
                        retry_descent = 0;
                        in = bucket;               /* initial bucket */

                        /* choose through intervening buckets */
                        flocal = 0;
                        do {
                                collide = 0;
                                retry_bucket = 0;
                                r = rep;
                                if (in->alg == CRUSH_BUCKET_UNIFORM) {
                                        /* be careful */
                                        if (firstn || numrep >= in->size)
                                                /* r' = r + f_total */
                                                r += ftotal;
                                        else if (in->size % numrep == 0)
                                                /* r'=r+(n+1)*f_local */
                                                r += (numrep+1) *
                                                        (flocal+ftotal);
                                        else
                                                /* r' = r + n*f_local */
                                                r += numrep * (flocal+ftotal);
                                } else {
                                        if (firstn)
                                                /* r' = r + f_total */
                                                r += ftotal;
                                        else
                                                /* r' = r + n*f_local */
                                                r += numrep * (flocal+ftotal);
                                }

                                /* bucket choose */
                                if (in->size == 0) {
                                        reject = 1;
                                        goto reject;
                                }
                                if (flocal >= (in->size>>1) &&
                                    flocal > orig_tries)
                                        item = bucket_perm_choose(in, x, r);
                                else
                                        item = crush_bucket_choose(in, x, r);
                                BUG_ON(item >= map->max_devices);

                                /* desired type? */
                                if (item < 0)
                                        itemtype = map->buckets[-1-item]->type;
                                else
                                        itemtype = 0;
                                dprintk("  item %d type %d\n", item, itemtype);

                                /* keep going? */
                                if (itemtype != type) {
                                        BUG_ON(item >= 0 ||
                                               (-1-item) >= map->max_buckets);
                                        in = map->buckets[-1-item];
                                        continue;
                                }

                                /* collision? */
                                for (i = 0; i < outpos; i++) {
                                        if (out[i] == item) {
                                                collide = 1;
                                                break;
                                        }
                                }

                                if (recurse_to_leaf &&
                                    item < 0 &&
                                    crush_choose(map, map->buckets[-1-item],
                                                 weight,
                                                 x, outpos+1, 0,
                                                 out2, outpos,
                                                 firstn, 0, NULL) <= outpos) {
                                        reject = 1;
                                } else {
                                        /* out? */
                                        if (itemtype == 0)
                                                reject = is_out(map, weight,
                                                                item, x);
                                        else
                                                reject = 0;
                                }

reject:
                                if (reject || collide) {
                                        ftotal++;
                                        flocal++;

                                        if (collide && flocal < 3)
                                                /* retry locally a few times */
                                                retry_bucket = 1;
                                        else if (flocal < in->size + orig_tries)
                                                /* exhaustive bucket search */
                                                retry_bucket = 1;
                                        else if (ftotal < 20)
                                                /* then retry descent */
                                                retry_descent = 1;
                                        else
                                                /* else give up */
                                                skip_rep = 1;
                                        dprintk("  reject %d  collide %d  "
                                                "ftotal %d  flocal %d\n",
                                                reject, collide, ftotal,
                                                flocal);
                                }
                        } while (retry_bucket);
                } while (retry_descent);

                if (skip_rep) {
                        dprintk("skip rep\n");
                        continue;
                }

                dprintk("choose got %d\n", item);
                out[outpos] = item;
                outpos++;
        }

        dprintk("choose returns %d\n", outpos);
        return outpos;
}


/**
 * crush_do_rule - calculate a mapping with the given input and rule
 * @map: the crush_map
 * @ruleno: the rule id
 * @x: hash input
 * @result: pointer to result vector
 * @result_max: maximum result size
 * @force: force initial replica choice; -1 for none
 */
int crush_do_rule(struct crush_map *map,
                  int ruleno, int x, int *result, int result_max,
                  int force, __u32 *weight)
{
        int result_len;
        int force_context[CRUSH_MAX_DEPTH];
        int force_pos = -1;
        int a[CRUSH_MAX_SET];
        int b[CRUSH_MAX_SET];
        int c[CRUSH_MAX_SET];
        int recurse_to_leaf;
        int *w;
        int wsize = 0;
        int *o;
        int osize;
        int *tmp;
        struct crush_rule *rule;
        int step;
        int i, j;
        int numrep;
        int firstn;
        int rc = -1;

        BUG_ON(ruleno >= map->max_rules);

        rule = map->rules[ruleno];
        result_len = 0;
        w = a;
        o = b;

        /*
         * determine hierarchical context of force, if any.  note
         * that this may or may not correspond to the specific types
         * referenced by the crush rule.
         */
        if (force >= 0) {
                if (force >= map->max_devices ||
                    map->device_parents[force] == 0) {
                        /*dprintk("CRUSH: forcefed device dne\n");*/
                        rc = -1;  /* force fed device dne */
                        goto out;
                }
                if (!is_out(map, weight, force, x)) {
                        while (1) {
                                force_context[++force_pos] = force;
                                if (force >= 0)
                                        force = map->device_parents[force];
                                else
                                        force = map->bucket_parents[-1-force];
                                if (force == 0)
                                        break;
                        }
                }
        }

        for (step = 0; step < rule->len; step++) {
                firstn = 0;
                switch (rule->steps[step].op) {
                case CRUSH_RULE_TAKE:
                        w[0] = rule->steps[step].arg1;
                        if (force_pos >= 0) {
                                BUG_ON(force_context[force_pos] != w[0]);
                                force_pos--;
                        }
                        wsize = 1;
                        break;

                case CRUSH_RULE_CHOOSE_LEAF_FIRSTN:
                case CRUSH_RULE_CHOOSE_FIRSTN:
                        firstn = 1;
                case CRUSH_RULE_CHOOSE_LEAF_INDEP:
                case CRUSH_RULE_CHOOSE_INDEP:
                        BUG_ON(wsize == 0);

                        recurse_to_leaf =
                                rule->steps[step].op ==
                                 CRUSH_RULE_CHOOSE_LEAF_FIRSTN ||
                                rule->steps[step].op ==
                                CRUSH_RULE_CHOOSE_LEAF_INDEP;

                        /* reset output */
                        osize = 0;

                        for (i = 0; i < wsize; i++) {
                                /*
                                 * see CRUSH_N, CRUSH_N_MINUS macros.
                                 * basically, numrep <= 0 means relative to
                                 * the provided result_max
                                 */
                                numrep = rule->steps[step].arg1;
                                if (numrep <= 0) {
                                        numrep += result_max;
                                        if (numrep <= 0)
                                                continue;
                                }
                                j = 0;
                                if (osize == 0 && force_pos >= 0) {
                                        /* skip any intermediate types */
                                        while (force_pos &&
                                               force_context[force_pos] < 0 &&
                                               rule->steps[step].arg2 !=
                                               map->buckets[-1 -
                                               force_context[force_pos]]->type)
                                                force_pos--;
                                        o[osize] = force_context[force_pos];
                                        if (recurse_to_leaf)
                                                c[osize] = force_context[0];
                                        j++;
                                        force_pos--;
                                }
                                osize += crush_choose(map,
                                                      map->buckets[-1-w[i]],
                                                      weight,
                                                      x, numrep,
                                                      rule->steps[step].arg2,
                                                      o+osize, j,
                                                      firstn,
                                                      recurse_to_leaf, c+osize);
                        }

                        if (recurse_to_leaf)
                                /* copy final _leaf_ values to output set */
                                memcpy(o, c, osize*sizeof(*o));

                        /* swap t and w arrays */
                        tmp = o;
                        o = w;
                        w = tmp;
                        wsize = osize;
                        break;


                case CRUSH_RULE_EMIT:
                        for (i = 0; i < wsize && result_len < result_max; i++) {
                                result[result_len] = w[i];
                                result_len++;
                        }
                        wsize = 0;
                        break;

                default:
                        BUG_ON(1);
                }
        }
        rc = result_len;

out:
        return rc;
}