ceph: factor out libceph from Ceph file system
This factors out protocol and low-level storage parts of ceph into a
separate libceph module living in net/ceph and include/linux/ceph. This
is mostly a matter of moving files around. However, a few key pieces
of the interface change as well:
- ceph_client becomes ceph_fs_client and ceph_client, where the latter
captures the mon and osd clients, and the fs_client gets the mds client
and file system specific pieces.
- Mount option parsing and debugfs setup is correspondingly broken into
two pieces.
- The mon client gets a generic handler callback for otherwise unknown
messages (mds map, in this case).
- The basic supported/required feature bits can be expanded (and are by
ceph_fs_client).
No functional change, aside from some subtle error handling cases that got
cleaned up in the refactoring process.
Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/net/ceph/crush/crush.c b/net/ceph/crush/crush.c
new file mode 100644
index 0000000..d6ebb13
--- /dev/null
+++ b/net/ceph/crush/crush.c
@@ -0,0 +1,151 @@
+
+#ifdef __KERNEL__
+# include <linux/slab.h>
+#else
+# include <stdlib.h>
+# include <assert.h>
+# define kfree(x) do { if (x) free(x); } while (0)
+# define BUG_ON(x) assert(!(x))
+#endif
+
+#include <linux/crush/crush.h>
+
+const char *crush_bucket_alg_name(int alg)
+{
+ switch (alg) {
+ case CRUSH_BUCKET_UNIFORM: return "uniform";
+ case CRUSH_BUCKET_LIST: return "list";
+ case CRUSH_BUCKET_TREE: return "tree";
+ case CRUSH_BUCKET_STRAW: return "straw";
+ default: return "unknown";
+ }
+}
+
+/**
+ * crush_get_bucket_item_weight - Get weight of an item in given bucket
+ * @b: bucket pointer
+ * @p: item index in bucket
+ */
+int crush_get_bucket_item_weight(struct crush_bucket *b, int p)
+{
+ if (p >= b->size)
+ return 0;
+
+ switch (b->alg) {
+ case CRUSH_BUCKET_UNIFORM:
+ return ((struct crush_bucket_uniform *)b)->item_weight;
+ case CRUSH_BUCKET_LIST:
+ return ((struct crush_bucket_list *)b)->item_weights[p];
+ case CRUSH_BUCKET_TREE:
+ if (p & 1)
+ return ((struct crush_bucket_tree *)b)->node_weights[p];
+ return 0;
+ case CRUSH_BUCKET_STRAW:
+ return ((struct crush_bucket_straw *)b)->item_weights[p];
+ }
+ return 0;
+}
+
+/**
+ * crush_calc_parents - Calculate parent vectors for the given crush map.
+ * @map: crush_map pointer
+ */
+void crush_calc_parents(struct crush_map *map)
+{
+ int i, b, c;
+
+ for (b = 0; b < map->max_buckets; b++) {
+ if (map->buckets[b] == NULL)
+ continue;
+ for (i = 0; i < map->buckets[b]->size; i++) {
+ c = map->buckets[b]->items[i];
+ BUG_ON(c >= map->max_devices ||
+ c < -map->max_buckets);
+ if (c >= 0)
+ map->device_parents[c] = map->buckets[b]->id;
+ else
+ map->bucket_parents[-1-c] = map->buckets[b]->id;
+ }
+ }
+}
+
+void crush_destroy_bucket_uniform(struct crush_bucket_uniform *b)
+{
+ kfree(b->h.perm);
+ kfree(b->h.items);
+ kfree(b);
+}
+
+void crush_destroy_bucket_list(struct crush_bucket_list *b)
+{
+ kfree(b->item_weights);
+ kfree(b->sum_weights);
+ kfree(b->h.perm);
+ kfree(b->h.items);
+ kfree(b);
+}
+
+void crush_destroy_bucket_tree(struct crush_bucket_tree *b)
+{
+ kfree(b->node_weights);
+ kfree(b);
+}
+
+void crush_destroy_bucket_straw(struct crush_bucket_straw *b)
+{
+ kfree(b->straws);
+ kfree(b->item_weights);
+ kfree(b->h.perm);
+ kfree(b->h.items);
+ kfree(b);
+}
+
+void crush_destroy_bucket(struct crush_bucket *b)
+{
+ switch (b->alg) {
+ case CRUSH_BUCKET_UNIFORM:
+ crush_destroy_bucket_uniform((struct crush_bucket_uniform *)b);
+ break;
+ case CRUSH_BUCKET_LIST:
+ crush_destroy_bucket_list((struct crush_bucket_list *)b);
+ break;
+ case CRUSH_BUCKET_TREE:
+ crush_destroy_bucket_tree((struct crush_bucket_tree *)b);
+ break;
+ case CRUSH_BUCKET_STRAW:
+ crush_destroy_bucket_straw((struct crush_bucket_straw *)b);
+ break;
+ }
+}
+
+/**
+ * crush_destroy - Destroy a crush_map
+ * @map: crush_map pointer
+ */
+void crush_destroy(struct crush_map *map)
+{
+ int b;
+
+ /* buckets */
+ if (map->buckets) {
+ for (b = 0; b < map->max_buckets; b++) {
+ if (map->buckets[b] == NULL)
+ continue;
+ crush_destroy_bucket(map->buckets[b]);
+ }
+ kfree(map->buckets);
+ }
+
+ /* rules */
+ if (map->rules) {
+ for (b = 0; b < map->max_rules; b++)
+ kfree(map->rules[b]);
+ kfree(map->rules);
+ }
+
+ kfree(map->bucket_parents);
+ kfree(map->device_parents);
+ kfree(map);
+}
+
+
diff --git a/net/ceph/crush/hash.c b/net/ceph/crush/hash.c
new file mode 100644
index 0000000..5bb63e3
--- /dev/null
+++ b/net/ceph/crush/hash.c
@@ -0,0 +1,149 @@
+
+#include <linux/types.h>
+#include <linux/crush/hash.h>
+
+/*
+ * Robert Jenkins' function for mixing 32-bit values
+ * http://burtleburtle.net/bob/hash/evahash.html
+ * a, b = random bits, c = input and output
+ */
+#define crush_hashmix(a, b, c) do { \
+ a = a-b; a = a-c; a = a^(c>>13); \
+ b = b-c; b = b-a; b = b^(a<<8); \
+ c = c-a; c = c-b; c = c^(b>>13); \
+ a = a-b; a = a-c; a = a^(c>>12); \
+ b = b-c; b = b-a; b = b^(a<<16); \
+ c = c-a; c = c-b; c = c^(b>>5); \
+ a = a-b; a = a-c; a = a^(c>>3); \
+ b = b-c; b = b-a; b = b^(a<<10); \
+ c = c-a; c = c-b; c = c^(b>>15); \
+ } while (0)
+
+#define crush_hash_seed 1315423911
+
+static __u32 crush_hash32_rjenkins1(__u32 a)
+{
+ __u32 hash = crush_hash_seed ^ a;
+ __u32 b = a;
+ __u32 x = 231232;
+ __u32 y = 1232;
+ crush_hashmix(b, x, hash);
+ crush_hashmix(y, a, hash);
+ return hash;
+}
+
+static __u32 crush_hash32_rjenkins1_2(__u32 a, __u32 b)
+{
+ __u32 hash = crush_hash_seed ^ a ^ b;
+ __u32 x = 231232;
+ __u32 y = 1232;
+ crush_hashmix(a, b, hash);
+ crush_hashmix(x, a, hash);
+ crush_hashmix(b, y, hash);
+ return hash;
+}
+
+static __u32 crush_hash32_rjenkins1_3(__u32 a, __u32 b, __u32 c)
+{
+ __u32 hash = crush_hash_seed ^ a ^ b ^ c;
+ __u32 x = 231232;
+ __u32 y = 1232;
+ crush_hashmix(a, b, hash);
+ crush_hashmix(c, x, hash);
+ crush_hashmix(y, a, hash);
+ crush_hashmix(b, x, hash);
+ crush_hashmix(y, c, hash);
+ return hash;
+}
+
+static __u32 crush_hash32_rjenkins1_4(__u32 a, __u32 b, __u32 c, __u32 d)
+{
+ __u32 hash = crush_hash_seed ^ a ^ b ^ c ^ d;
+ __u32 x = 231232;
+ __u32 y = 1232;
+ crush_hashmix(a, b, hash);
+ crush_hashmix(c, d, hash);
+ crush_hashmix(a, x, hash);
+ crush_hashmix(y, b, hash);
+ crush_hashmix(c, x, hash);
+ crush_hashmix(y, d, hash);
+ return hash;
+}
+
+static __u32 crush_hash32_rjenkins1_5(__u32 a, __u32 b, __u32 c, __u32 d,
+ __u32 e)
+{
+ __u32 hash = crush_hash_seed ^ a ^ b ^ c ^ d ^ e;
+ __u32 x = 231232;
+ __u32 y = 1232;
+ crush_hashmix(a, b, hash);
+ crush_hashmix(c, d, hash);
+ crush_hashmix(e, x, hash);
+ crush_hashmix(y, a, hash);
+ crush_hashmix(b, x, hash);
+ crush_hashmix(y, c, hash);
+ crush_hashmix(d, x, hash);
+ crush_hashmix(y, e, hash);
+ return hash;
+}
+
+
+__u32 crush_hash32(int type, __u32 a)
+{
+ switch (type) {
+ case CRUSH_HASH_RJENKINS1:
+ return crush_hash32_rjenkins1(a);
+ default:
+ return 0;
+ }
+}
+
+__u32 crush_hash32_2(int type, __u32 a, __u32 b)
+{
+ switch (type) {
+ case CRUSH_HASH_RJENKINS1:
+ return crush_hash32_rjenkins1_2(a, b);
+ default:
+ return 0;
+ }
+}
+
+__u32 crush_hash32_3(int type, __u32 a, __u32 b, __u32 c)
+{
+ switch (type) {
+ case CRUSH_HASH_RJENKINS1:
+ return crush_hash32_rjenkins1_3(a, b, c);
+ default:
+ return 0;
+ }
+}
+
+__u32 crush_hash32_4(int type, __u32 a, __u32 b, __u32 c, __u32 d)
+{
+ switch (type) {
+ case CRUSH_HASH_RJENKINS1:
+ return crush_hash32_rjenkins1_4(a, b, c, d);
+ default:
+ return 0;
+ }
+}
+
+__u32 crush_hash32_5(int type, __u32 a, __u32 b, __u32 c, __u32 d, __u32 e)
+{
+ switch (type) {
+ case CRUSH_HASH_RJENKINS1:
+ return crush_hash32_rjenkins1_5(a, b, c, d, e);
+ default:
+ return 0;
+ }
+}
+
+const char *crush_hash_name(int type)
+{
+ switch (type) {
+ case CRUSH_HASH_RJENKINS1:
+ return "rjenkins1";
+ default:
+ return "unknown";
+ }
+}
diff --git a/net/ceph/crush/mapper.c b/net/ceph/crush/mapper.c
new file mode 100644
index 0000000..42599e3
--- /dev/null
+++ b/net/ceph/crush/mapper.c
@@ -0,0 +1,609 @@
+
+#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;
+ 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;
+}
+
+