Adding upstream version 16.2.11+ds.upstream/16.2.11+dsupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1105 insertions, 0 deletions

diff --git a/src/crush/mapper.c b/src/crush/mapper.c
new file mode 100644
index 000000000..4ac572627
--- /dev/null
+++ b/src/crush/mapper.c
@@ -0,0 +1,1105 @@
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2015 Intel Corporation All Rights Reserved
+ *
+ * This is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software
+ * Foundation.  See file COPYING.
+ *
+ */
+
+#ifdef __KERNEL__
+# include <linux/string.h>
+# include <linux/slab.h>
+# include <linux/bug.h>
+# include <linux/kernel.h>
+# include <linux/crush/crush.h>
+# include <linux/crush/hash.h>
+#else
+# include "crush_compat.h"
+# include "crush.h"
+# include "hash.h"
+#endif
+#include "crush_ln_table.h"
+#include "mapper.h"
+
+#define dprintk(args...) /* printf(args) */
+
+/*
+ * 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(const struct crush_map *map, int ruleset, int type, int size)
+{
+	__u32 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(const struct crush_bucket *bucket,
+			      struct crush_work_bucket *work,
+			      int x, int r)
+{
+	unsigned int pr = r % bucket->size;
+	unsigned int i, s;
+
+	/* start a new permutation if @x has changed */
+	if (work->perm_x != (__u32)x || work->perm_n == 0) {
+		dprintk("bucket %d new x=%d\n", bucket->id, x);
+		work->perm_x = x;
+
+		/* optimize common r=0 case */
+		if (pr == 0) {
+			s = crush_hash32_3(bucket->hash, x, bucket->id, 0) %
+				bucket->size;
+			work->perm[0] = s;
+			work->perm_n = 0xffff;   /* magic value, see below */
+			goto out;
+		}
+
+		for (i = 0; i < bucket->size; i++)
+			work->perm[i] = i;
+		work->perm_n = 0;
+	} else if (work->perm_n == 0xffff) {
+		/* clean up after the r=0 case above */
+		for (i = 1; i < bucket->size; i++)
+			work->perm[i] = i;
+		work->perm[work->perm[0]] = 0;
+		work->perm_n = 1;
+	}
+
+	/* calculate permutation up to pr */
+	for (i = 0; i < work->perm_n; i++)
+		dprintk(" perm_choose have %d: %d\n", i, work->perm[i]);
+	while (work->perm_n <= pr) {
+		unsigned int p = work->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 = work->perm[p + i];
+				work->perm[p + i] = work->perm[p];
+				work->perm[p] = t;
+			}
+			dprintk(" perm_choose swap %d with %d\n", p, p+i);
+		}
+		work->perm_n++;
+	}
+	for (i = 0; i < bucket->size; i++)
+		dprintk(" perm_choose  %d: %d\n", i, work->perm[i]);
+
+	s = work->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(const struct crush_bucket_uniform *bucket,
+				 struct crush_work_bucket *work, int x, int r)
+{
+	return bucket_perm_choose(&bucket->h, work, x, r);
+}
+
+/* list */
+static int bucket_list_choose(const 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];
+		}
+	}
+
+	dprintk("bad list sums for bucket %d\n", bucket->h.id);
+	return bucket->h.items[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(const struct crush_bucket_tree *bucket,
+			      int x, int r)
+{
+	int n;
+	__u32 w;
+	__u64 t;
+
+	/* start at root */
+	n = bucket->num_nodes >> 1;
+
+	while (!terminal(n)) {
+		int l;
+		/* 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(const struct crush_bucket_straw *bucket,
+			       int x, int r)
+{
+	__u32 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];
+}
+
+/* compute 2^44*log2(input+1) */
+static __u64 crush_ln(unsigned int xin)
+{
+	unsigned int x = xin;
+	int iexpon, index1, index2;
+	__u64 RH, LH, LL, xl64, result;
+
+	x++;
+
+	/* normalize input */
+	iexpon = 15;
+
+	// figure out number of bits we need to shift and
+	// do it in one step instead of iteratively
+	if (!(x & 0x18000)) {
+	  int bits = __builtin_clz(x & 0x1FFFF) - 16;
+	  x <<= bits;
+	  iexpon = 15 - bits;
+	}
+
+	index1 = (x >> 8) << 1;
+	/* RH ~ 2^56/index1 */
+	RH = __RH_LH_tbl[index1 - 256];
+	/* LH ~ 2^48 * log2(index1/256) */
+	LH = __RH_LH_tbl[index1 + 1 - 256];
+
+	/* RH*x ~ 2^48 * (2^15 + xf), xf<2^8 */
+	xl64 = (__s64)x * RH;
+	xl64 >>= 48;
+
+	result = iexpon;
+	result <<= (12 + 32);
+
+	index2 = xl64 & 0xff;
+	/* LL ~ 2^48*log2(1.0+index2/2^15) */
+	LL = __LL_tbl[index2];
+
+	LH = LH + LL;
+
+	LH >>= (48 - 12 - 32);
+	result += LH;
+
+	return result;
+}
+
+
+/*
+ * straw2
+ *
+ * Suppose we have two osds: osd.0 and osd.1, with weight 8 and 4 respectively, It means:
+ *   a). For osd.0, the time interval between each io request apply to exponential distribution 
+ *       with lamba equals 8
+ *   b). For osd.1, the time interval between each io request apply to exponential distribution 
+ *       with lamba equals 4
+ *   c). If we apply to each osd's exponential random variable, then the total pgs on each osd
+ *       is proportional to its weight.
+ *
+ * for reference, see:
+ *
+ * http://en.wikipedia.org/wiki/Exponential_distribution#Distribution_of_the_minimum_of_exponential_random_variables
+ */
+
+static inline __u32 *get_choose_arg_weights(const struct crush_bucket_straw2 *bucket,
+                                            const struct crush_choose_arg *arg,
+                                            int position)
+{
+	if ((arg == NULL) || (arg->weight_set == NULL))
+		return bucket->item_weights;
+	if (position >= arg->weight_set_positions)
+		position = arg->weight_set_positions - 1;
+	return arg->weight_set[position].weights;
+}
+
+static inline __s32 *get_choose_arg_ids(const struct crush_bucket_straw2 *bucket,
+					const struct crush_choose_arg *arg)
+{
+	if ((arg == NULL) || (arg->ids == NULL))
+		return bucket->h.items;
+	return arg->ids;
+}
+
+/*
+ * Compute exponential random variable using inversion method.
+ *
+ * for reference, see the exponential distribution example at:  
+ * https://en.wikipedia.org/wiki/Inverse_transform_sampling#Examples
+ */
+static inline __s64 generate_exponential_distribution(int type, int x, int y, int z, 
+                                                      int weight)
+{
+	unsigned int u = crush_hash32_3(type, x, y, z);
+	u &= 0xffff;
+
+	/*
+	 * for some reason slightly less than 0x10000 produces
+	 * a slightly more accurate distribution... probably a
+	 * rounding effect.
+	 *
+	 * the natural log lookup table maps [0,0xffff]
+	 * (corresponding to real numbers [1/0x10000, 1] to
+	 * [0, 0xffffffffffff] (corresponding to real numbers
+	 * [-11.090355,0]).
+	 */
+	__s64 ln = crush_ln(u) - 0x1000000000000ll;
+
+	/*
+	 * divide by 16.16 fixed-point weight.  note
+	 * that the ln value is negative, so a larger
+	 * weight means a larger (less negative) value
+	 * for draw.
+	 */
+	return div64_s64(ln, weight);
+}
+
+static int bucket_straw2_choose(const struct crush_bucket_straw2 *bucket,
+				int x, int r, const struct crush_choose_arg *arg,
+                                int position)
+{
+	unsigned int i, high = 0;
+	__s64 draw, high_draw = 0;
+        __u32 *weights = get_choose_arg_weights(bucket, arg, position);
+        __s32 *ids = get_choose_arg_ids(bucket, arg);
+	for (i = 0; i < bucket->h.size; i++) {
+                dprintk("weight 0x%x item %d\n", weights[i], ids[i]);
+		if (weights[i]) {
+			draw = generate_exponential_distribution(bucket->h.hash, x, ids[i], r, weights[i]);
+		} else {
+			draw = S64_MIN;
+		}
+
+		if (i == 0 || draw > high_draw) {
+			high = i;
+			high_draw = draw;
+		}
+	}
+
+	return bucket->h.items[high];
+}
+
+
+static int crush_bucket_choose(const struct crush_bucket *in,
+			       struct crush_work_bucket *work,
+			       int x, int r,
+                               const struct crush_choose_arg *arg,
+                               int position)
+{
+	dprintk(" crush_bucket_choose %d x=%d r=%d\n", in->id, x, r);
+	BUG_ON(in->size == 0);
+	switch (in->alg) {
+	case CRUSH_BUCKET_UNIFORM:
+		return bucket_uniform_choose(
+			(const struct crush_bucket_uniform *)in,
+			work, x, r);
+	case CRUSH_BUCKET_LIST:
+		return bucket_list_choose((const struct crush_bucket_list *)in,
+					  x, r);
+	case CRUSH_BUCKET_TREE:
+		return bucket_tree_choose((const struct crush_bucket_tree *)in,
+					  x, r);
+	case CRUSH_BUCKET_STRAW:
+		return bucket_straw_choose(
+			(const struct crush_bucket_straw *)in,
+			x, r);
+	case CRUSH_BUCKET_STRAW2:
+		return bucket_straw2_choose(
+			(const struct crush_bucket_straw2 *)in,
+			x, r, arg, position);
+	default:
+		dprintk("unknown bucket %d alg %d\n", in->id, in->alg);
+		return in->items[0];
+	}
+}
+
+/*
+ * true if device is marked "out" (failed, fully offloaded)
+ * of the cluster
+ */
+static int is_out(const struct crush_map *map,
+		  const __u32 *weight, int weight_max,
+		  int item, int x)
+{
+	if (item >= weight_max)
+		return 1;
+	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_firstn - 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
+ * @out_size: size of the out vector
+ * @tries: number of attempts to make
+ * @recurse_tries: number of attempts to have recursive chooseleaf make
+ * @local_retries: localized retries
+ * @local_fallback_retries: localized fallback retries
+ * @recurse_to_leaf: true if we want one device under each item of given type (chooseleaf instead of choose)
+ * @stable: stable mode starts rep=0 in the recursive call for all replicas
+ * @vary_r: pass r to recursive calls
+ * @out2: second output vector for leaf items (if @recurse_to_leaf)
+ * @parent_r: r value passed from the parent
+ */
+static int crush_choose_firstn(const struct crush_map *map,
+			       struct crush_work *work,
+			       const struct crush_bucket *bucket,
+			       const __u32 *weight, int weight_max,
+			       int x, int numrep, int type,
+			       int *out, int outpos,
+			       int out_size,
+			       unsigned int tries,
+			       unsigned int recurse_tries,
+			       unsigned int local_retries,
+			       unsigned int local_fallback_retries,
+			       int recurse_to_leaf,
+			       unsigned int vary_r,
+			       unsigned int stable,
+			       int *out2,
+			       int parent_r,
+                               const struct crush_choose_arg *choose_args)
+{
+	int rep;
+	unsigned int ftotal, flocal;
+	int retry_descent, retry_bucket, skip_rep;
+	const struct crush_bucket *in = bucket;
+	int r;
+	int i;
+	int item = 0;
+	int itemtype;
+	int collide, reject;
+	int count = out_size;
+
+	dprintk("CHOOSE%s bucket %d x %d outpos %d numrep %d tries %d \
+recurse_tries %d local_retries %d local_fallback_retries %d \
+parent_r %d stable %d\n",
+		recurse_to_leaf ? "_LEAF" : "",
+		bucket->id, x, outpos, numrep,
+		tries, recurse_tries, local_retries, local_fallback_retries,
+		parent_r, stable);
+
+	for (rep = stable ? 0 : outpos; rep < numrep && count > 0 ; 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 + parent_r;
+				/* r' = r + f_total */
+				r += ftotal;
+
+				/* bucket choose */
+				if (in->size == 0) {
+					reject = 1;
+					goto reject;
+				}
+				if (local_fallback_retries > 0 &&
+				    flocal >= (in->size>>1) &&
+				    flocal > local_fallback_retries)
+					item = bucket_perm_choose(
+						in, work->work[-1-in->id],
+						x, r);
+				else
+					item = crush_bucket_choose(
+						in, work->work[-1-in->id],
+						x, r,
+                                                (choose_args ? &choose_args[-1-in->id] : 0),
+                                                outpos);
+				if (item >= map->max_devices) {
+					dprintk("   bad item %d\n", item);
+					skip_rep = 1;
+					break;
+				}
+
+				/* 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) {
+					if (item >= 0 ||
+					    (-1-item) >= map->max_buckets) {
+						dprintk("   bad item type %d\n", type);
+						skip_rep = 1;
+						break;
+					}
+					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 (!collide && recurse_to_leaf) {
+					if (item < 0) {
+						int sub_r;
+						if (vary_r)
+							sub_r = r >> (vary_r-1);
+						else
+							sub_r = 0;
+						if (crush_choose_firstn(
+							    map,
+							    work,
+							    map->buckets[-1-item],
+							    weight, weight_max,
+							    x, stable ? 1 : outpos+1, 0,
+							    out2, outpos, count,
+							    recurse_tries, 0,
+							    local_retries,
+							    local_fallback_retries,
+							    0,
+							    vary_r,
+							    stable,
+							    NULL,
+							    sub_r,
+                                                            choose_args) <= outpos)
+							/* didn't get leaf */
+							reject = 1;
+					} else {
+						/* we already have a leaf! */
+						out2[outpos] = item;
+		                        }
+				}
+
+				if (!reject && !collide) {
+					/* out? */
+					if (itemtype == 0)
+						reject = is_out(map, weight,
+								weight_max,
+								item, x);
+				}
+
+reject:
+				if (reject || collide) {
+					ftotal++;
+					flocal++;
+
+					if (collide && flocal <= local_retries)
+						/* retry locally a few times */
+						retry_bucket = 1;
+					else if (local_fallback_retries > 0 &&
+						 flocal <= in->size + local_fallback_retries)
+						/* exhaustive bucket search */
+						retry_bucket = 1;
+					else if (ftotal < tries)
+						/* then retry descent */
+						retry_descent = 1;
+					else
+						/* else give up */
+						skip_rep = 1;
+					dprintk("  reject %d  collide %d  "
+						"ftotal %u  flocal %u\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++;
+		count--;
+#ifndef __KERNEL__
+		if (map->choose_tries && ftotal <= map->choose_total_tries)
+			map->choose_tries[ftotal]++;
+#endif
+	}
+
+	dprintk("CHOOSE returns %d\n", outpos);
+	return outpos;
+}
+
+
+/**
+ * crush_choose_indep: alternative breadth-first positionally stable mapping
+ *
+ */
+static void crush_choose_indep(const struct crush_map *map,
+			       struct crush_work *work,
+			       const struct crush_bucket *bucket,
+			       const __u32 *weight, int weight_max,
+			       int x, int left, int numrep, int type,
+			       int *out, int outpos,
+			       unsigned int tries,
+			       unsigned int recurse_tries,
+			       int recurse_to_leaf,
+			       int *out2,
+			       int parent_r,
+                               const struct crush_choose_arg *choose_args)
+{
+	const struct crush_bucket *in = bucket;
+	int endpos = outpos + left;
+	int rep;
+	unsigned int ftotal;
+	int r;
+	int i;
+	int item = 0;
+	int itemtype;
+	int collide;
+
+	dprintk("CHOOSE%s INDEP bucket %d x %d outpos %d numrep %d\n", recurse_to_leaf ? "_LEAF" : "",
+		bucket->id, x, outpos, numrep);
+
+	/* initially my result is undefined */
+	for (rep = outpos; rep < endpos; rep++) {
+		out[rep] = CRUSH_ITEM_UNDEF;
+		if (out2)
+			out2[rep] = CRUSH_ITEM_UNDEF;
+	}
+
+	for (ftotal = 0; left > 0 && ftotal < tries; ftotal++) {
+#ifdef DEBUG_INDEP
+		if (out2 && ftotal) {
+			dprintk("%u %d a: ", ftotal, left);
+			for (rep = outpos; rep < endpos; rep++) {
+				dprintk(" %d", out[rep]);
+			}
+			dprintk("\n");
+			dprintk("%u %d b: ", ftotal, left);
+			for (rep = outpos; rep < endpos; rep++) {
+				dprintk(" %d", out2[rep]);
+			}
+			dprintk("\n");
+		}
+#endif
+		for (rep = outpos; rep < endpos; rep++) {
+			if (out[rep] != CRUSH_ITEM_UNDEF)
+				continue;
+
+			in = bucket;  /* initial bucket */
+
+			/* choose through intervening buckets */
+			for (;;) {
+				/* note: we base the choice on the position
+				 * even in the nested call.  that means that
+				 * if the first layer chooses the same bucket
+				 * in a different position, we will tend to
+				 * choose a different item in that bucket.
+				 * this will involve more devices in data
+				 * movement and tend to distribute the load.
+				 */
+				r = rep + parent_r;
+
+				/* be careful */
+				if (in->alg == CRUSH_BUCKET_UNIFORM &&
+				    in->size % numrep == 0)
+					/* r'=r+(n+1)*f_total */
+					r += (numrep+1) * ftotal;
+				else
+					/* r' = r + n*f_total */
+					r += numrep * ftotal;
+
+				/* bucket choose */
+				if (in->size == 0) {
+					dprintk("   empty bucket\n");
+					break;
+				}
+
+				item = crush_bucket_choose(
+					in, work->work[-1-in->id],
+					x, r,
+                                        (choose_args ? &choose_args[-1-in->id] : 0),
+                                        outpos);
+				if (item >= map->max_devices) {
+					dprintk("   bad item %d\n", item);
+					out[rep] = CRUSH_ITEM_NONE;
+					if (out2)
+						out2[rep] = CRUSH_ITEM_NONE;
+					left--;
+					break;
+				}
+
+				/* 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) {
+					if (item >= 0 ||
+					    (-1-item) >= map->max_buckets) {
+						dprintk("   bad item type %d\n", type);
+						out[rep] = CRUSH_ITEM_NONE;
+						if (out2)
+							out2[rep] =
+								CRUSH_ITEM_NONE;
+						left--;
+						break;
+					}
+					in = map->buckets[-1-item];
+					continue;
+				}
+
+				/* collision? */
+				collide = 0;
+				for (i = outpos; i < endpos; i++) {
+					if (out[i] == item) {
+						collide = 1;
+						break;
+					}
+				}
+				if (collide)
+					break;
+
+				if (recurse_to_leaf) {
+					if (item < 0) {
+						crush_choose_indep(
+							map,
+							work,
+							map->buckets[-1-item],
+							weight, weight_max,
+							x, 1, numrep, 0,
+							out2, rep,
+							recurse_tries, 0,
+							0, NULL, r, choose_args);
+						if (out2 && out2[rep] == CRUSH_ITEM_NONE) {
+							/* placed nothing; no leaf */
+							break;
+						}
+					} else if (out2) {
+						/* we already have a leaf! */
+						out2[rep] = item;
+					}
+				}
+
+				/* out? */
+				if (itemtype == 0 &&
+				    is_out(map, weight, weight_max, item, x))
+					break;
+
+				/* yay! */
+				out[rep] = item;
+				left--;
+				break;
+			}
+		}
+	}
+	for (rep = outpos; rep < endpos; rep++) {
+		if (out[rep] == CRUSH_ITEM_UNDEF) {
+			out[rep] = CRUSH_ITEM_NONE;
+		}
+		if (out2 && out2[rep] == CRUSH_ITEM_UNDEF) {
+			out2[rep] = CRUSH_ITEM_NONE;
+		}
+	}
+#ifndef __KERNEL__
+	if (map->choose_tries && ftotal <= map->choose_total_tries)
+		map->choose_tries[ftotal]++;
+#endif
+#ifdef DEBUG_INDEP
+	if (out2) {
+		dprintk("%u %d a: ", ftotal, left);
+		for (rep = outpos; rep < endpos; rep++) {
+			dprintk(" %d", out[rep]);
+		}
+		dprintk("\n");
+		dprintk("%u %d b: ", ftotal, left);
+		for (rep = outpos; rep < endpos; rep++) {
+			dprintk(" %d", out2[rep]);
+		}
+		dprintk("\n");
+	}
+#endif
+}
+
+
+/* This takes a chunk of memory and sets it up to be a shiny new
+   working area for a CRUSH placement computation. It must be called
+   on any newly allocated memory before passing it in to
+   crush_do_rule. It may be used repeatedly after that, so long as the
+   map has not changed. If the map /has/ changed, you must make sure
+   the working size is no smaller than what was allocated and re-run
+   crush_init_workspace.
+
+   If you do retain the working space between calls to crush, make it
+   thread-local. If you reinstitute the locking I've spent so much
+   time getting rid of, I will be very unhappy with you. */
+
+void crush_init_workspace(const struct crush_map *m, void *v) {
+	/* We work by moving through the available space and setting
+	   values and pointers as we go.
+
+	   It's a bit like Forth's use of the 'allot' word since we
+	   set the pointer first and then reserve the space for it to
+	   point to by incrementing the point. */
+	struct crush_work *w = (struct crush_work *)v;
+	char *point = (char *)v;
+	__s32 b;
+	point += sizeof(struct crush_work);
+	w->work = (struct crush_work_bucket **)point;
+	point += m->max_buckets * sizeof(struct crush_work_bucket *);
+	for (b = 0; b < m->max_buckets; ++b) {
+		if (m->buckets[b] == 0)
+			continue;
+
+		w->work[b] = (struct crush_work_bucket *) point;
+		switch (m->buckets[b]->alg) {
+		default:
+			point += sizeof(struct crush_work_bucket);
+			break;
+		}
+		w->work[b]->perm_x = 0;
+		w->work[b]->perm_n = 0;
+		w->work[b]->perm = (__u32 *)point;
+		point += m->buckets[b]->size * sizeof(__u32);
+	}
+	BUG_ON((char *)point - (char *)w != m->working_size);
+}
+
+/**
+ * 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
+ * @weight: weight vector (for map leaves)
+ * @weight_max: size of weight vector
+ * @cwin: Pointer to at least map->working_size bytes of memory or NULL.
+ */
+int crush_do_rule(const struct crush_map *map,
+		  int ruleno, int x, int *result, int result_max,
+		  const __u32 *weight, int weight_max,
+		  void *cwin, const struct crush_choose_arg *choose_args)
+{
+	int result_len;
+	struct crush_work *cw = cwin;
+	int *a = (int *)((char *)cw + map->working_size);
+	int *b = a + result_max;
+	int *c = b + result_max;
+	int *w = a;
+	int *o = b;
+	int recurse_to_leaf;
+	int wsize = 0;
+	int osize;
+	int *tmp;
+	const struct crush_rule *rule;
+	__u32 step;
+	int i, j;
+	int numrep;
+	int out_size;
+	/*
+	 * the original choose_total_tries value was off by one (it
+	 * counted "retries" and not "tries").  add one.
+	 */
+	int choose_tries = map->choose_total_tries + 1;
+	int choose_leaf_tries = 0;
+	/*
+	 * the local tries values were counted as "retries", though,
+	 * and need no adjustment
+	 */
+	int choose_local_retries = map->choose_local_tries;
+	int choose_local_fallback_retries = map->choose_local_fallback_tries;
+
+	int vary_r = map->chooseleaf_vary_r;
+	int stable = map->chooseleaf_stable;
+
+	if ((__u32)ruleno >= map->max_rules) {
+		dprintk(" bad ruleno %d\n", ruleno);
+		return 0;
+	}
+
+	rule = map->rules[ruleno];
+	result_len = 0;
+
+	for (step = 0; step < rule->len; step++) {
+		int firstn = 0;
+		const struct crush_rule_step *curstep = &rule->steps[step];
+
+		switch (curstep->op) {
+		case CRUSH_RULE_TAKE:
+			if ((curstep->arg1 >= 0 &&
+			     curstep->arg1 < map->max_devices) ||
+			    (-1-curstep->arg1 >= 0 &&
+			     -1-curstep->arg1 < map->max_buckets &&
+			     map->buckets[-1-curstep->arg1])) {
+				w[0] = curstep->arg1;
+				wsize = 1;
+			} else {
+				dprintk(" bad take value %d\n", curstep->arg1);
+			}
+			break;
+
+		case CRUSH_RULE_SET_CHOOSE_TRIES:
+			if (curstep->arg1 > 0)
+				choose_tries = curstep->arg1;
+			break;
+
+		case CRUSH_RULE_SET_CHOOSELEAF_TRIES:
+			if (curstep->arg1 > 0)
+				choose_leaf_tries = curstep->arg1;
+			break;
+
+		case CRUSH_RULE_SET_CHOOSE_LOCAL_TRIES:
+			if (curstep->arg1 >= 0)
+				choose_local_retries = curstep->arg1;
+			break;
+
+		case CRUSH_RULE_SET_CHOOSE_LOCAL_FALLBACK_TRIES:
+			if (curstep->arg1 >= 0)
+				choose_local_fallback_retries = curstep->arg1;
+			break;
+
+		case CRUSH_RULE_SET_CHOOSELEAF_VARY_R:
+			if (curstep->arg1 >= 0)
+				vary_r = curstep->arg1;
+			break;
+
+		case CRUSH_RULE_SET_CHOOSELEAF_STABLE:
+			if (curstep->arg1 >= 0)
+				stable = curstep->arg1;
+			break;
+
+		case CRUSH_RULE_CHOOSELEAF_FIRSTN:
+		case CRUSH_RULE_CHOOSE_FIRSTN:
+			firstn = 1;
+			/* fall through */
+		case CRUSH_RULE_CHOOSELEAF_INDEP:
+		case CRUSH_RULE_CHOOSE_INDEP:
+			if (wsize == 0)
+				break;
+
+			recurse_to_leaf =
+				curstep->op ==
+				 CRUSH_RULE_CHOOSELEAF_FIRSTN ||
+				curstep->op ==
+				CRUSH_RULE_CHOOSELEAF_INDEP;
+
+			/* reset output */
+			osize = 0;
+
+			for (i = 0; i < wsize; i++) {
+				int bno;
+				numrep = curstep->arg1;
+				if (numrep <= 0) {
+					numrep += result_max;
+					if (numrep <= 0)
+						continue;
+				}
+				j = 0;
+				/* make sure bucket id is valid */
+				bno = -1 - w[i];
+				if (bno < 0 || bno >= map->max_buckets) {
+					// w[i] is probably CRUSH_ITEM_NONE
+					dprintk("  bad w[i] %d\n", w[i]);
+					continue;
+				}
+				if (firstn) {
+					int recurse_tries;
+					if (choose_leaf_tries)
+						recurse_tries =
+							choose_leaf_tries;
+					else if (map->chooseleaf_descend_once)
+						recurse_tries = 1;
+					else
+						recurse_tries = choose_tries;
+					osize += crush_choose_firstn(
+						map,
+						cw,
+						map->buckets[bno],
+						weight, weight_max,
+						x, numrep,
+						curstep->arg2,
+						o+osize, j,
+						result_max-osize,
+						choose_tries,
+						recurse_tries,
+						choose_local_retries,
+						choose_local_fallback_retries,
+						recurse_to_leaf,
+						vary_r,
+						stable,
+						c+osize,
+						0,
+						choose_args);
+				} else {
+					out_size = ((numrep < (result_max-osize)) ?
+						    numrep : (result_max-osize));
+					crush_choose_indep(
+						map,
+						cw,
+						map->buckets[bno],
+						weight, weight_max,
+						x, out_size, numrep,
+						curstep->arg2,
+						o+osize, j,
+						choose_tries,
+						choose_leaf_tries ?
+						   choose_leaf_tries : 1,
+						recurse_to_leaf,
+						c+osize,
+						0,
+						choose_args);
+					osize += out_size;
+				}
+			}
+
+			if (recurse_to_leaf)
+				/* copy final _leaf_ values to output set */
+				memcpy(o, c, osize*sizeof(*o));
+
+			/* swap o 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:
+			dprintk(" unknown op %d at step %d\n",
+				curstep->op, step);
+			break;
+		}
+	}
+
+	return result_len;
+}