[linux-2.6-block.git] / net / 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 <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 int pr = r % bucket->size;
	unsigned int 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 int 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 int 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;
}
Commit	Line	Data
5ecc0a0f SW	1
	2	#ifdef __KERNEL__
	3	# include <linux/string.h>
	4	# include <linux/slab.h>
	5	# include <linux/bug.h>
	6	# include <linux/kernel.h>
	7	# ifndef dprintk
	8	# define dprintk(args...)
	9	# endif
	10	#else
	11	# include <string.h>
	12	# include <stdio.h>
	13	# include <stdlib.h>
	14	# include <assert.h>
	15	# define BUG_ON(x) assert(!(x))
	16	# define dprintk(args...) /* printf(args) */
	17	# define kmalloc(x, f) malloc(x)
	18	# define kfree(x) free(x)
	19	#endif
	20
3d14c5d2 YS	21	#include <linux/crush/crush.h>
3d14c5d2 YS	22	#include <linux/crush/hash.h>
5ecc0a0f SW	23
	24	/*
	25	* Implement the core CRUSH mapping algorithm.
	26	*/
	27
	28	/**
	29	* crush_find_rule - find a crush_rule id for a given ruleset, type, and size.
	30	* @map: the crush_map
	31	* @ruleset: the storage ruleset id (user defined)
	32	* @type: storage ruleset type (user defined)
	33	* @size: output set size
	34	*/
	35	int crush_find_rule(struct crush_map *map, int ruleset, int type, int size)
	36	{
	37	int i;
	38
	39	for (i = 0; i < map->max_rules; i++) {
	40	if (map->rules[i] &&
	41	map->rules[i]->mask.ruleset == ruleset &&
	42	map->rules[i]->mask.type == type &&
	43	map->rules[i]->mask.min_size <= size &&
	44	map->rules[i]->mask.max_size >= size)
	45	return i;
	46	}
	47	return -1;
	48	}
	49
	50
	51	/*
	52	* bucket choose methods
	53	*
	54	* For each bucket algorithm, we have a "choose" method that, given a
	55	* crush input @x and replica position (usually, position in output set) @r,
	56	* will produce an item in the bucket.
	57	*/
	58
	59	/*
	60	* Choose based on a random permutation of the bucket.
	61	*
	62	* We used to use some prime number arithmetic to do this, but it
	63	* wasn't very random, and had some other bad behaviors. Instead, we
	64	* calculate an actual random permutation of the bucket members.
	65	* Since this is expensive, we optimize for the r=0 case, which
	66	* captures the vast majority of calls.
	67	*/
	68	static int bucket_perm_choose(struct crush_bucket *bucket,
	69	int x, int r)
	70	{
95c96174 ED	71	unsigned int pr = r % bucket->size;
95c96174 ED	72	unsigned int i, s;
5ecc0a0f SW	73
	74	/* start a new permutation if @x has changed */
	75	if (bucket->perm_x != x \|\| bucket->perm_n == 0) {
	76	dprintk("bucket %d new x=%d\n", bucket->id, x);
	77	bucket->perm_x = x;
	78
	79	/* optimize common r=0 case */
	80	if (pr == 0) {
fb690390	81	s = crush_hash32_3(bucket->hash, x, bucket->id, 0) %
5ecc0a0f SW	82	bucket->size;
	83	bucket->perm[0] = s;
	84	bucket->perm_n = 0xffff; /* magic value, see below */
	85	goto out;
	86	}
	87
	88	for (i = 0; i < bucket->size; i++)
	89	bucket->perm[i] = i;
	90	bucket->perm_n = 0;
	91	} else if (bucket->perm_n == 0xffff) {
	92	/* clean up after the r=0 case above */
	93	for (i = 1; i < bucket->size; i++)
	94	bucket->perm[i] = i;
	95	bucket->perm[bucket->perm[0]] = 0;
	96	bucket->perm_n = 1;
	97	}
	98
	99	/* calculate permutation up to pr */
	100	for (i = 0; i < bucket->perm_n; i++)
	101	dprintk(" perm_choose have %d: %d\n", i, bucket->perm[i]);
	102	while (bucket->perm_n <= pr) {
95c96174	103	unsigned int p = bucket->perm_n;
5ecc0a0f SW	104	/* no point in swapping the final entry */
5ecc0a0f SW	105	if (p < bucket->size - 1) {
fb690390	106	i = crush_hash32_3(bucket->hash, x, bucket->id, p) %
5ecc0a0f SW	107	(bucket->size - p);
5ecc0a0f SW	108	if (i) {
95c96174	109	unsigned int t = bucket->perm[p + i];
5ecc0a0f SW	110	bucket->perm[p + i] = bucket->perm[p];
	111	bucket->perm[p] = t;
	112	}
	113	dprintk(" perm_choose swap %d with %d\n", p, p+i);
	114	}
	115	bucket->perm_n++;
	116	}
	117	for (i = 0; i < bucket->size; i++)
	118	dprintk(" perm_choose %d: %d\n", i, bucket->perm[i]);
	119
	120	s = bucket->perm[pr];
	121	out:
	122	dprintk(" perm_choose %d sz=%d x=%d r=%d (%d) s=%d\n", bucket->id,
	123	bucket->size, x, r, pr, s);
	124	return bucket->items[s];
	125	}
	126
	127	/* uniform */
	128	static int bucket_uniform_choose(struct crush_bucket_uniform *bucket,
	129	int x, int r)
	130	{
	131	return bucket_perm_choose(&bucket->h, x, r);
	132	}
	133
	134	/* list */
	135	static int bucket_list_choose(struct crush_bucket_list *bucket,
	136	int x, int r)
	137	{
	138	int i;
	139
	140	for (i = bucket->h.size-1; i >= 0; i--) {
fb690390 SW	141	__u64 w = crush_hash32_4(bucket->h.hash,x, bucket->h.items[i],
fb690390 SW	142	r, bucket->h.id);
5ecc0a0f SW	143	w &= 0xffff;
	144	dprintk("list_choose i=%d x=%d r=%d item %d weight %x "
	145	"sw %x rand %llx",
	146	i, x, r, bucket->h.items[i], bucket->item_weights[i],
	147	bucket->sum_weights[i], w);
	148	w *= bucket->sum_weights[i];
	149	w = w >> 16;
	150	/dprintk(" scaled %llx\n", w);/
	151	if (w < bucket->item_weights[i])
	152	return bucket->h.items[i];
	153	}
	154
	155	BUG_ON(1);
	156	return 0;
	157	}
	158
	159
	160	/* (binary) tree */
	161	static int height(int n)
	162	{
	163	int h = 0;
	164	while ((n & 1) == 0) {
	165	h++;
	166	n = n >> 1;
	167	}
	168	return h;
	169	}
	170
	171	static int left(int x)
	172	{
	173	int h = height(x);
	174	return x - (1 << (h-1));
	175	}
	176
	177	static int right(int x)
	178	{
	179	int h = height(x);
	180	return x + (1 << (h-1));
	181	}
	182
	183	static int terminal(int x)
	184	{
	185	return x & 1;
	186	}
	187
	188	static int bucket_tree_choose(struct crush_bucket_tree *bucket,
	189	int x, int r)
	190	{
	191	int n, l;
	192	__u32 w;
	193	__u64 t;
	194
	195	/* start at root */
	196	n = bucket->num_nodes >> 1;
	197
	198	while (!terminal(n)) {
	199	/* pick point in [0, w) */
	200	w = bucket->node_weights[n];
fb690390 SW	201	t = (__u64)crush_hash32_4(bucket->h.hash, x, n, r,
fb690390 SW	202	bucket->h.id) * (__u64)w;
5ecc0a0f SW	203	t = t >> 32;
	204
	205	/* descend to the left or right? */
	206	l = left(n);
	207	if (t < bucket->node_weights[l])
	208	n = l;
	209	else
	210	n = right(n);
	211	}
	212
	213	return bucket->h.items[n >> 1];
	214	}
	215
	216
	217	/* straw */
	218
	219	static int bucket_straw_choose(struct crush_bucket_straw *bucket,
	220	int x, int r)
	221	{
	222	int i;
	223	int high = 0;
	224	__u64 high_draw = 0;
	225	__u64 draw;
	226
	227	for (i = 0; i < bucket->h.size; i++) {
fb690390	228	draw = crush_hash32_3(bucket->h.hash, x, bucket->h.items[i], r);
5ecc0a0f SW	229	draw &= 0xffff;
	230	draw *= bucket->straws[i];
	231	if (i == 0 \|\| draw > high_draw) {
	232	high = i;
	233	high_draw = draw;
	234	}
	235	}
	236	return bucket->h.items[high];
	237	}
	238
	239	static int crush_bucket_choose(struct crush_bucket *in, int x, int r)
	240	{
a1a31e73	241	dprintk(" crush_bucket_choose %d x=%d r=%d\n", in->id, x, r);
5ecc0a0f SW	242	switch (in->alg) {
	243	case CRUSH_BUCKET_UNIFORM:
	244	return bucket_uniform_choose((struct crush_bucket_uniform *)in,
	245	x, r);
	246	case CRUSH_BUCKET_LIST:
	247	return bucket_list_choose((struct crush_bucket_list *)in,
	248	x, r);
	249	case CRUSH_BUCKET_TREE:
	250	return bucket_tree_choose((struct crush_bucket_tree *)in,
	251	x, r);
	252	case CRUSH_BUCKET_STRAW:
	253	return bucket_straw_choose((struct crush_bucket_straw *)in,
	254	x, r);
	255	default:
	256	BUG_ON(1);
50b885b9	257	return in->items[0];
5ecc0a0f SW	258	}
	259	}
	260
	261	/*
	262	* true if device is marked "out" (failed, fully offloaded)
	263	* of the cluster
	264	*/
	265	static int is_out(struct crush_map map, __u32 weight, int item, int x)
	266	{
153a1093	267	if (weight[item] >= 0x10000)
5ecc0a0f SW	268	return 0;
	269	if (weight[item] == 0)
	270	return 1;
fb690390 SW	271	if ((crush_hash32_2(CRUSH_HASH_RJENKINS1, x, item) & 0xffff)
fb690390 SW	272	< weight[item])
5ecc0a0f SW	273	return 0;
	274	return 1;
	275	}
	276
	277	/**
	278	* crush_choose - choose numrep distinct items of given type
	279	* @map: the crush_map
	280	* @bucket: the bucket we are choose an item from
	281	* @x: crush input value
	282	* @numrep: the number of items to choose
	283	* @type: the type of item to choose
	284	* @out: pointer to output vector
	285	* @outpos: our position in that vector
	286	* @firstn: true if choosing "first n" items, false if choosing "indep"
	287	* @recurse_to_leaf: true if we want one device under each item of given type
	288	* @out2: second output vector for leaf items (if @recurse_to_leaf)
	289	*/
	290	static int crush_choose(struct crush_map *map,
	291	struct crush_bucket *bucket,
	292	__u32 *weight,
	293	int x, int numrep, int type,
	294	int *out, int outpos,
	295	int firstn, int recurse_to_leaf,
	296	int *out2)
	297	{
	298	int rep;
	299	int ftotal, flocal;
	300	int retry_descent, retry_bucket, skip_rep;
	301	struct crush_bucket *in = bucket;
	302	int r;
	303	int i;
b28813a6	304	int item = 0;
5ecc0a0f SW	305	int itemtype;
	306	int collide, reject;
	307	const int orig_tries = 5; /* attempts before we fall back to search */
a1a31e73 SW	308
	309	dprintk("CHOOSE%s bucket %d x %d outpos %d numrep %d\n", recurse_to_leaf ? "_LEAF" : "",
	310	bucket->id, x, outpos, numrep);
5ecc0a0f SW	311
	312	for (rep = outpos; rep < numrep; rep++) {
	313	/* keep trying until we get a non-out, non-colliding item */
	314	ftotal = 0;
	315	skip_rep = 0;
	316	do {
	317	retry_descent = 0;
	318	in = bucket; /* initial bucket */
	319
	320	/* choose through intervening buckets */
	321	flocal = 0;
	322	do {
b28813a6	323	collide = 0;
5ecc0a0f SW	324	retry_bucket = 0;
	325	r = rep;
	326	if (in->alg == CRUSH_BUCKET_UNIFORM) {
	327	/* be careful */
	328	if (firstn \|\| numrep >= in->size)
	329	/* r' = r + f_total */
	330	r += ftotal;
	331	else if (in->size % numrep == 0)
	332	/* r'=r+(n+1)f_local /
	333	r += (numrep+1) *
	334	(flocal+ftotal);
	335	else
	336	/* r' = r + nf_local /
	337	r += numrep * (flocal+ftotal);
	338	} else {
	339	if (firstn)
	340	/* r' = r + f_total */
	341	r += ftotal;
	342	else
	343	/* r' = r + nf_local /
	344	r += numrep * (flocal+ftotal);
	345	}
	346
	347	/* bucket choose */
b28813a6 SW	348	if (in->size == 0) {
	349	reject = 1;
	350	goto reject;
	351	}
5ecc0a0f SW	352	if (flocal >= (in->size>>1) &&
	353	flocal > orig_tries)
	354	item = bucket_perm_choose(in, x, r);
	355	else
	356	item = crush_bucket_choose(in, x, r);
	357	BUG_ON(item >= map->max_devices);
	358
	359	/* desired type? */
	360	if (item < 0)
	361	itemtype = map->buckets[-1-item]->type;
	362	else
	363	itemtype = 0;
	364	dprintk(" item %d type %d\n", item, itemtype);
	365
	366	/* keep going? */
	367	if (itemtype != type) {
	368	BUG_ON(item >= 0 \|\|
	369	(-1-item) >= map->max_buckets);
	370	in = map->buckets[-1-item];
55bda7aa	371	retry_bucket = 1;
5ecc0a0f SW	372	continue;
	373	}
	374
	375	/* collision? */
5ecc0a0f SW	376	for (i = 0; i < outpos; i++) {
	377	if (out[i] == item) {
	378	collide = 1;
	379	break;
	380	}
	381	}
	382
a1a31e73 SW	383	reject = 0;
	384	if (recurse_to_leaf) {
	385	if (item < 0) {
	386	if (crush_choose(map,
	387	map->buckets[-1-item],
	388	weight,
	389	x, outpos+1, 0,
	390	out2, outpos,
	391	firstn, 0,
	392	NULL) <= outpos)
	393	/* didn't get leaf */
	394	reject = 1;
	395	} else {
	396	/* we already have a leaf! */
	397	out2[outpos] = item;
	398	}
	399	}
	400
	401	if (!reject) {
5ecc0a0f SW	402	/* out? */
	403	if (itemtype == 0)
	404	reject = is_out(map, weight,
	405	item, x);
	406	else
	407	reject = 0;
	408	}
	409
b28813a6	410	reject:
5ecc0a0f SW	411	if (reject \|\| collide) {
	412	ftotal++;
	413	flocal++;
	414
	415	if (collide && flocal < 3)
	416	/* retry locally a few times */
	417	retry_bucket = 1;
	418	else if (flocal < in->size + orig_tries)
	419	/* exhaustive bucket search */
	420	retry_bucket = 1;
	421	else if (ftotal < 20)
	422	/* then retry descent */
	423	retry_descent = 1;
	424	else
	425	/* else give up */
	426	skip_rep = 1;
	427	dprintk(" reject %d collide %d "
	428	"ftotal %d flocal %d\n",
	429	reject, collide, ftotal,
	430	flocal);
	431	}
	432	} while (retry_bucket);
	433	} while (retry_descent);
	434
	435	if (skip_rep) {
	436	dprintk("skip rep\n");
	437	continue;
	438	}
	439
a1a31e73	440	dprintk("CHOOSE got %d\n", item);
5ecc0a0f SW	441	out[outpos] = item;
	442	outpos++;
	443	}
	444
a1a31e73	445	dprintk("CHOOSE returns %d\n", outpos);
5ecc0a0f SW	446	return outpos;
	447	}
	448
	449
	450	/**
	451	* crush_do_rule - calculate a mapping with the given input and rule
	452	* @map: the crush_map
	453	* @ruleno: the rule id
	454	* @x: hash input
	455	* @result: pointer to result vector
	456	* @result_max: maximum result size
	457	* @force: force initial replica choice; -1 for none
	458	*/
	459	int crush_do_rule(struct crush_map *map,
	460	int ruleno, int x, int *result, int result_max,
	461	int force, __u32 *weight)
	462	{
	463	int result_len;
	464	int force_context[CRUSH_MAX_DEPTH];
	465	int force_pos = -1;
	466	int a[CRUSH_MAX_SET];
	467	int b[CRUSH_MAX_SET];
	468	int c[CRUSH_MAX_SET];
	469	int recurse_to_leaf;
	470	int *w;
	471	int wsize = 0;
	472	int *o;
	473	int osize;
	474	int *tmp;
	475	struct crush_rule *rule;
	476	int step;
	477	int i, j;
	478	int numrep;
	479	int firstn;
5ecc0a0f SW	480
	481	BUG_ON(ruleno >= map->max_rules);
	482
	483	rule = map->rules[ruleno];
	484	result_len = 0;
	485	w = a;
	486	o = b;
	487
	488	/*
	489	* determine hierarchical context of force, if any. note
	490	* that this may or may not correspond to the specific types
	491	* referenced by the crush rule.
	492	*/
f1932fc1 SW	493	if (force >= 0 &&
	494	force < map->max_devices &&
	495	map->device_parents[force] != 0 &&
	496	!is_out(map, weight, force, x)) {
	497	while (1) {
	498	force_context[++force_pos] = force;
	499	if (force >= 0)
	500	force = map->device_parents[force];
	501	else
	502	force = map->bucket_parents[-1-force];
	503	if (force == 0)
	504	break;
5ecc0a0f SW	505	}
	506	}
	507
	508	for (step = 0; step < rule->len; step++) {
	509	firstn = 0;
	510	switch (rule->steps[step].op) {
	511	case CRUSH_RULE_TAKE:
	512	w[0] = rule->steps[step].arg1;
e11b05d3 SW	513
	514	/* find position in force_context/hierarchy */
	515	while (force_pos >= 0 &&
	516	force_context[force_pos] != w[0])
5ecc0a0f	517	force_pos--;
e11b05d3 SW	518	/* and move past it */
	519	if (force_pos >= 0)
	520	force_pos--;
	521
5ecc0a0f SW	522	wsize = 1;
	523	break;
	524
	525	case CRUSH_RULE_CHOOSE_LEAF_FIRSTN:
	526	case CRUSH_RULE_CHOOSE_FIRSTN:
	527	firstn = 1;
	528	case CRUSH_RULE_CHOOSE_LEAF_INDEP:
	529	case CRUSH_RULE_CHOOSE_INDEP:
	530	BUG_ON(wsize == 0);
	531
	532	recurse_to_leaf =
	533	rule->steps[step].op ==
	534	CRUSH_RULE_CHOOSE_LEAF_FIRSTN \|\|
	535	rule->steps[step].op ==
	536	CRUSH_RULE_CHOOSE_LEAF_INDEP;
	537
	538	/* reset output */
	539	osize = 0;
	540
	541	for (i = 0; i < wsize; i++) {
	542	/*
	543	* see CRUSH_N, CRUSH_N_MINUS macros.
	544	* basically, numrep <= 0 means relative to
	545	* the provided result_max
	546	*/
	547	numrep = rule->steps[step].arg1;
	548	if (numrep <= 0) {
	549	numrep += result_max;
	550	if (numrep <= 0)
	551	continue;
	552	}
	553	j = 0;
	554	if (osize == 0 && force_pos >= 0) {
	555	/* skip any intermediate types */
	556	while (force_pos &&
	557	force_context[force_pos] < 0 &&
	558	rule->steps[step].arg2 !=
	559	map->buckets[-1 -
	560	force_context[force_pos]]->type)
	561	force_pos--;
	562	o[osize] = force_context[force_pos];
	563	if (recurse_to_leaf)
	564	c[osize] = force_context[0];
	565	j++;
	566	force_pos--;
	567	}
	568	osize += crush_choose(map,
	569	map->buckets[-1-w[i]],
	570	weight,
	571	x, numrep,
	572	rule->steps[step].arg2,
	573	o+osize, j,
	574	firstn,
	575	recurse_to_leaf, c+osize);
	576	}
	577
	578	if (recurse_to_leaf)
	579	/* copy final _leaf_ values to output set */
	580	memcpy(o, c, osizesizeof(o));
	581
	582	/* swap t and w arrays */
	583	tmp = o;
	584	o = w;
	585	w = tmp;
586	wsize = osize;
587	break;
588
589
590	case CRUSH_RULE_EMIT:
591	for (i = 0; i < wsize && result_len < result_max; i++) {
592	result[result_len] = w[i];
593	result_len++;
594	}
595	wsize = 0;
596	break;
597
598	default:
599	BUG_ON(1);
600	}
601	}
f1932fc1	602	return result_len;
5ecc0a0f SW	603	}
	604
	605