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