text: 
  #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 <linux/crush/crush.h>
  #include <linux/crush/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(" crush_bucket_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] >= 0x10000)
  		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%s bucket %d x %d outpos %d numrep %d\n", recurse_to_leaf ? "_LEAF" : "",
  		bucket->id, x, outpos, numrep);
  
  	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];
  					retry_bucket = 1;
  					continue;
  				}
  
  				/* collision? */
  				for (i = 0; i < outpos; i++) {
  					if (out[i] == item) {
  						collide = 1;
  						break;
  					}
  				}
  
  				reject = 0;
  				if (recurse_to_leaf) {
  					if (item < 0) {
  						if (crush_choose(map,
  							 map->buckets[-1-item],
  							 weight,
  							 x, outpos+1, 0,
  							 out2, outpos,
  							 firstn, 0,
  							 NULL) <= outpos)
  							/* didn't get leaf */
  							reject = 1;
  					} else {
  						/* we already have a leaf! */
  						out2[outpos] = item;
  					}
  				}
  
  				if (!reject) {
  					/* 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;
  
  	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 &&
  	    force < map->max_devices &&
  	    map->device_parents[force] != 0 &&
  	    !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;
  
  			/* find position in force_context/hierarchy */
  			while (force_pos >= 0 &&
  			       force_context[force_pos] != w[0])
  				force_pos--;
  			/* and move past it */
  			if (force_pos >= 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);
  		}
  	}
  	return result_len;
  }
  
  
  