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Linux/lib/objagg.c

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  1 // SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
  2 /* Copyright (c) 2018 Mellanox Technologies. All rights reserved */
  3 
  4 #include <linux/module.h>
  5 #include <linux/slab.h>
  6 #include <linux/rhashtable.h>
  7 #include <linux/idr.h>
  8 #include <linux/list.h>
  9 #include <linux/sort.h>
 10 #include <linux/objagg.h>
 11 
 12 #define CREATE_TRACE_POINTS
 13 #include <trace/events/objagg.h>
 14 
 15 struct objagg_hints {
 16         struct rhashtable node_ht;
 17         struct rhashtable_params ht_params;
 18         struct list_head node_list;
 19         unsigned int node_count;
 20         unsigned int root_count;
 21         unsigned int refcount;
 22         const struct objagg_ops *ops;
 23 };
 24 
 25 struct objagg_hints_node {
 26         struct rhash_head ht_node; /* member of objagg_hints->node_ht */
 27         struct list_head list; /* member of objagg_hints->node_list */
 28         struct objagg_hints_node *parent;
 29         unsigned int root_id;
 30         struct objagg_obj_stats_info stats_info;
 31         unsigned long obj[];
 32 };
 33 
 34 static struct objagg_hints_node *
 35 objagg_hints_lookup(struct objagg_hints *objagg_hints, void *obj)
 36 {
 37         if (!objagg_hints)
 38                 return NULL;
 39         return rhashtable_lookup_fast(&objagg_hints->node_ht, obj,
 40                                       objagg_hints->ht_params);
 41 }
 42 
 43 struct objagg {
 44         const struct objagg_ops *ops;
 45         void *priv;
 46         struct rhashtable obj_ht;
 47         struct rhashtable_params ht_params;
 48         struct list_head obj_list;
 49         unsigned int obj_count;
 50         struct ida root_ida;
 51         struct objagg_hints *hints;
 52 };
 53 
 54 struct objagg_obj {
 55         struct rhash_head ht_node; /* member of objagg->obj_ht */
 56         struct list_head list; /* member of objagg->obj_list */
 57         struct objagg_obj *parent; /* if the object is nested, this
 58                                     * holds pointer to parent, otherwise NULL
 59                                     */
 60         union {
 61                 void *delta_priv; /* user delta private */
 62                 void *root_priv; /* user root private */
 63         };
 64         unsigned int root_id;
 65         unsigned int refcount; /* counts number of users of this object
 66                                 * including nested objects
 67                                 */
 68         struct objagg_obj_stats stats;
 69         unsigned long obj[];
 70 };
 71 
 72 static unsigned int objagg_obj_ref_inc(struct objagg_obj *objagg_obj)
 73 {
 74         return ++objagg_obj->refcount;
 75 }
 76 
 77 static unsigned int objagg_obj_ref_dec(struct objagg_obj *objagg_obj)
 78 {
 79         return --objagg_obj->refcount;
 80 }
 81 
 82 static void objagg_obj_stats_inc(struct objagg_obj *objagg_obj)
 83 {
 84         objagg_obj->stats.user_count++;
 85         objagg_obj->stats.delta_user_count++;
 86         if (objagg_obj->parent)
 87                 objagg_obj->parent->stats.delta_user_count++;
 88 }
 89 
 90 static void objagg_obj_stats_dec(struct objagg_obj *objagg_obj)
 91 {
 92         objagg_obj->stats.user_count--;
 93         objagg_obj->stats.delta_user_count--;
 94         if (objagg_obj->parent)
 95                 objagg_obj->parent->stats.delta_user_count--;
 96 }
 97 
 98 static bool objagg_obj_is_root(const struct objagg_obj *objagg_obj)
 99 {
100         /* Nesting is not supported, so we can use ->parent
101          * to figure out if the object is root.
102          */
103         return !objagg_obj->parent;
104 }
105 
106 /**
107  * objagg_obj_root_priv - obtains root private for an object
108  * @objagg_obj: objagg object instance
109  *
110  * Note: all locking must be provided by the caller.
111  *
112  * Either the object is root itself when the private is returned
113  * directly, or the parent is root and its private is returned
114  * instead.
115  *
116  * Returns a user private root pointer.
117  */
118 const void *objagg_obj_root_priv(const struct objagg_obj *objagg_obj)
119 {
120         if (objagg_obj_is_root(objagg_obj))
121                 return objagg_obj->root_priv;
122         WARN_ON(!objagg_obj_is_root(objagg_obj->parent));
123         return objagg_obj->parent->root_priv;
124 }
125 EXPORT_SYMBOL(objagg_obj_root_priv);
126 
127 /**
128  * objagg_obj_delta_priv - obtains delta private for an object
129  * @objagg_obj: objagg object instance
130  *
131  * Note: all locking must be provided by the caller.
132  *
133  * Returns user private delta pointer or NULL in case the passed
134  * object is root.
135  */
136 const void *objagg_obj_delta_priv(const struct objagg_obj *objagg_obj)
137 {
138         if (objagg_obj_is_root(objagg_obj))
139                 return NULL;
140         return objagg_obj->delta_priv;
141 }
142 EXPORT_SYMBOL(objagg_obj_delta_priv);
143 
144 /**
145  * objagg_obj_raw - obtains object user private pointer
146  * @objagg_obj: objagg object instance
147  *
148  * Note: all locking must be provided by the caller.
149  *
150  * Returns user private pointer as was passed to objagg_obj_get() by "obj" arg.
151  */
152 const void *objagg_obj_raw(const struct objagg_obj *objagg_obj)
153 {
154         return objagg_obj->obj;
155 }
156 EXPORT_SYMBOL(objagg_obj_raw);
157 
158 static struct objagg_obj *objagg_obj_lookup(struct objagg *objagg, void *obj)
159 {
160         return rhashtable_lookup_fast(&objagg->obj_ht, obj, objagg->ht_params);
161 }
162 
163 static int objagg_obj_parent_assign(struct objagg *objagg,
164                                     struct objagg_obj *objagg_obj,
165                                     struct objagg_obj *parent,
166                                     bool take_parent_ref)
167 {
168         void *delta_priv;
169 
170         delta_priv = objagg->ops->delta_create(objagg->priv, parent->obj,
171                                                objagg_obj->obj);
172         if (IS_ERR(delta_priv))
173                 return PTR_ERR(delta_priv);
174 
175         /* User returned a delta private, that means that
176          * our object can be aggregated into the parent.
177          */
178         objagg_obj->parent = parent;
179         objagg_obj->delta_priv = delta_priv;
180         if (take_parent_ref)
181                 objagg_obj_ref_inc(objagg_obj->parent);
182         trace_objagg_obj_parent_assign(objagg, objagg_obj,
183                                        parent,
184                                        parent->refcount);
185         return 0;
186 }
187 
188 static int objagg_obj_parent_lookup_assign(struct objagg *objagg,
189                                            struct objagg_obj *objagg_obj)
190 {
191         struct objagg_obj *objagg_obj_cur;
192         int err;
193 
194         list_for_each_entry(objagg_obj_cur, &objagg->obj_list, list) {
195                 /* Nesting is not supported. In case the object
196                  * is not root, it cannot be assigned as parent.
197                  */
198                 if (!objagg_obj_is_root(objagg_obj_cur))
199                         continue;
200                 err = objagg_obj_parent_assign(objagg, objagg_obj,
201                                                objagg_obj_cur, true);
202                 if (!err)
203                         return 0;
204         }
205         return -ENOENT;
206 }
207 
208 static void __objagg_obj_put(struct objagg *objagg,
209                              struct objagg_obj *objagg_obj);
210 
211 static void objagg_obj_parent_unassign(struct objagg *objagg,
212                                        struct objagg_obj *objagg_obj)
213 {
214         trace_objagg_obj_parent_unassign(objagg, objagg_obj,
215                                          objagg_obj->parent,
216                                          objagg_obj->parent->refcount);
217         objagg->ops->delta_destroy(objagg->priv, objagg_obj->delta_priv);
218         __objagg_obj_put(objagg, objagg_obj->parent);
219 }
220 
221 static int objagg_obj_root_id_alloc(struct objagg *objagg,
222                                     struct objagg_obj *objagg_obj,
223                                     struct objagg_hints_node *hnode)
224 {
225         unsigned int min, max;
226         int root_id;
227 
228         /* In case there are no hints available, the root id is invalid. */
229         if (!objagg->hints) {
230                 objagg_obj->root_id = OBJAGG_OBJ_ROOT_ID_INVALID;
231                 return 0;
232         }
233 
234         if (hnode) {
235                 min = hnode->root_id;
236                 max = hnode->root_id;
237         } else {
238                 /* For objects with no hint, start after the last
239                  * hinted root_id.
240                  */
241                 min = objagg->hints->root_count;
242                 max = ~0;
243         }
244 
245         root_id = ida_alloc_range(&objagg->root_ida, min, max, GFP_KERNEL);
246 
247         if (root_id < 0)
248                 return root_id;
249         objagg_obj->root_id = root_id;
250         return 0;
251 }
252 
253 static void objagg_obj_root_id_free(struct objagg *objagg,
254                                     struct objagg_obj *objagg_obj)
255 {
256         if (!objagg->hints)
257                 return;
258         ida_free(&objagg->root_ida, objagg_obj->root_id);
259 }
260 
261 static int objagg_obj_root_create(struct objagg *objagg,
262                                   struct objagg_obj *objagg_obj,
263                                   struct objagg_hints_node *hnode)
264 {
265         int err;
266 
267         err = objagg_obj_root_id_alloc(objagg, objagg_obj, hnode);
268         if (err)
269                 return err;
270         objagg_obj->root_priv = objagg->ops->root_create(objagg->priv,
271                                                          objagg_obj->obj,
272                                                          objagg_obj->root_id);
273         if (IS_ERR(objagg_obj->root_priv)) {
274                 err = PTR_ERR(objagg_obj->root_priv);
275                 goto err_root_create;
276         }
277         trace_objagg_obj_root_create(objagg, objagg_obj);
278         return 0;
279 
280 err_root_create:
281         objagg_obj_root_id_free(objagg, objagg_obj);
282         return err;
283 }
284 
285 static void objagg_obj_root_destroy(struct objagg *objagg,
286                                     struct objagg_obj *objagg_obj)
287 {
288         trace_objagg_obj_root_destroy(objagg, objagg_obj);
289         objagg->ops->root_destroy(objagg->priv, objagg_obj->root_priv);
290         objagg_obj_root_id_free(objagg, objagg_obj);
291 }
292 
293 static struct objagg_obj *__objagg_obj_get(struct objagg *objagg, void *obj);
294 
295 static int objagg_obj_init_with_hints(struct objagg *objagg,
296                                       struct objagg_obj *objagg_obj,
297                                       bool *hint_found)
298 {
299         struct objagg_hints_node *hnode;
300         struct objagg_obj *parent;
301         int err;
302 
303         hnode = objagg_hints_lookup(objagg->hints, objagg_obj->obj);
304         if (!hnode) {
305                 *hint_found = false;
306                 return 0;
307         }
308         *hint_found = true;
309 
310         if (!hnode->parent)
311                 return objagg_obj_root_create(objagg, objagg_obj, hnode);
312 
313         parent = __objagg_obj_get(objagg, hnode->parent->obj);
314         if (IS_ERR(parent))
315                 return PTR_ERR(parent);
316 
317         err = objagg_obj_parent_assign(objagg, objagg_obj, parent, false);
318         if (err) {
319                 *hint_found = false;
320                 err = 0;
321                 goto err_parent_assign;
322         }
323 
324         return 0;
325 
326 err_parent_assign:
327         objagg_obj_put(objagg, parent);
328         return err;
329 }
330 
331 static int objagg_obj_init(struct objagg *objagg,
332                            struct objagg_obj *objagg_obj)
333 {
334         bool hint_found;
335         int err;
336 
337         /* First, try to use hints if they are available and
338          * if they provide result.
339          */
340         err = objagg_obj_init_with_hints(objagg, objagg_obj, &hint_found);
341         if (err)
342                 return err;
343 
344         if (hint_found)
345                 return 0;
346 
347         /* Try to find if the object can be aggregated under an existing one. */
348         err = objagg_obj_parent_lookup_assign(objagg, objagg_obj);
349         if (!err)
350                 return 0;
351         /* If aggregation is not possible, make the object a root. */
352         return objagg_obj_root_create(objagg, objagg_obj, NULL);
353 }
354 
355 static void objagg_obj_fini(struct objagg *objagg,
356                             struct objagg_obj *objagg_obj)
357 {
358         if (!objagg_obj_is_root(objagg_obj))
359                 objagg_obj_parent_unassign(objagg, objagg_obj);
360         else
361                 objagg_obj_root_destroy(objagg, objagg_obj);
362 }
363 
364 static struct objagg_obj *objagg_obj_create(struct objagg *objagg, void *obj)
365 {
366         struct objagg_obj *objagg_obj;
367         int err;
368 
369         objagg_obj = kzalloc(sizeof(*objagg_obj) + objagg->ops->obj_size,
370                              GFP_KERNEL);
371         if (!objagg_obj)
372                 return ERR_PTR(-ENOMEM);
373         objagg_obj_ref_inc(objagg_obj);
374         memcpy(objagg_obj->obj, obj, objagg->ops->obj_size);
375 
376         err = objagg_obj_init(objagg, objagg_obj);
377         if (err)
378                 goto err_obj_init;
379 
380         err = rhashtable_insert_fast(&objagg->obj_ht, &objagg_obj->ht_node,
381                                      objagg->ht_params);
382         if (err)
383                 goto err_ht_insert;
384         list_add(&objagg_obj->list, &objagg->obj_list);
385         objagg->obj_count++;
386         trace_objagg_obj_create(objagg, objagg_obj);
387 
388         return objagg_obj;
389 
390 err_ht_insert:
391         objagg_obj_fini(objagg, objagg_obj);
392 err_obj_init:
393         kfree(objagg_obj);
394         return ERR_PTR(err);
395 }
396 
397 static struct objagg_obj *__objagg_obj_get(struct objagg *objagg, void *obj)
398 {
399         struct objagg_obj *objagg_obj;
400 
401         /* First, try to find the object exactly as user passed it,
402          * perhaps it is already in use.
403          */
404         objagg_obj = objagg_obj_lookup(objagg, obj);
405         if (objagg_obj) {
406                 objagg_obj_ref_inc(objagg_obj);
407                 return objagg_obj;
408         }
409 
410         return objagg_obj_create(objagg, obj);
411 }
412 
413 /**
414  * objagg_obj_get - gets an object within objagg instance
415  * @objagg:     objagg instance
416  * @obj:        user-specific private object pointer
417  *
418  * Note: all locking must be provided by the caller.
419  *
420  * Size of the "obj" memory is specified in "objagg->ops".
421  *
422  * There are 3 main options this function wraps:
423  * 1) The object according to "obj" already exist. In that case
424  *    the reference counter is incrementes and the object is returned.
425  * 2) The object does not exist, but it can be aggregated within
426  *    another object. In that case, user ops->delta_create() is called
427  *    to obtain delta data and a new object is created with returned
428  *    user-delta private pointer.
429  * 3) The object does not exist and cannot be aggregated into
430  *    any of the existing objects. In that case, user ops->root_create()
431  *    is called to create the root and a new object is created with
432  *    returned user-root private pointer.
433  *
434  * Returns a pointer to objagg object instance in case of success,
435  * otherwise it returns pointer error using ERR_PTR macro.
436  */
437 struct objagg_obj *objagg_obj_get(struct objagg *objagg, void *obj)
438 {
439         struct objagg_obj *objagg_obj;
440 
441         objagg_obj = __objagg_obj_get(objagg, obj);
442         if (IS_ERR(objagg_obj))
443                 return objagg_obj;
444         objagg_obj_stats_inc(objagg_obj);
445         trace_objagg_obj_get(objagg, objagg_obj, objagg_obj->refcount);
446         return objagg_obj;
447 }
448 EXPORT_SYMBOL(objagg_obj_get);
449 
450 static void objagg_obj_destroy(struct objagg *objagg,
451                                struct objagg_obj *objagg_obj)
452 {
453         trace_objagg_obj_destroy(objagg, objagg_obj);
454         --objagg->obj_count;
455         list_del(&objagg_obj->list);
456         rhashtable_remove_fast(&objagg->obj_ht, &objagg_obj->ht_node,
457                                objagg->ht_params);
458         objagg_obj_fini(objagg, objagg_obj);
459         kfree(objagg_obj);
460 }
461 
462 static void __objagg_obj_put(struct objagg *objagg,
463                              struct objagg_obj *objagg_obj)
464 {
465         if (!objagg_obj_ref_dec(objagg_obj))
466                 objagg_obj_destroy(objagg, objagg_obj);
467 }
468 
469 /**
470  * objagg_obj_put - puts an object within objagg instance
471  * @objagg:     objagg instance
472  * @objagg_obj: objagg object instance
473  *
474  * Note: all locking must be provided by the caller.
475  *
476  * Symmetric to objagg_obj_get().
477  */
478 void objagg_obj_put(struct objagg *objagg, struct objagg_obj *objagg_obj)
479 {
480         trace_objagg_obj_put(objagg, objagg_obj, objagg_obj->refcount);
481         objagg_obj_stats_dec(objagg_obj);
482         __objagg_obj_put(objagg, objagg_obj);
483 }
484 EXPORT_SYMBOL(objagg_obj_put);
485 
486 /**
487  * objagg_create - creates a new objagg instance
488  * @ops:                user-specific callbacks
489  * @objagg_hints:       hints, can be NULL
490  * @priv:               pointer to a private data passed to the ops
491  *
492  * Note: all locking must be provided by the caller.
493  *
494  * The purpose of the library is to provide an infrastructure to
495  * aggregate user-specified objects. Library does not care about the type
496  * of the object. User fills-up ops which take care of the specific
497  * user object manipulation.
498  *
499  * As a very stupid example, consider integer numbers. For example
500  * number 8 as a root object. That can aggregate number 9 with delta 1,
501  * number 10 with delta 2, etc. This example is implemented as
502  * a part of a testing module in test_objagg.c file.
503  *
504  * Each objagg instance contains multiple trees. Each tree node is
505  * represented by "an object". In the current implementation there can be
506  * only roots and leafs nodes. Leaf nodes are called deltas.
507  * But in general, this can be easily extended for intermediate nodes.
508  * In that extension, a delta would be associated with all non-root
509  * nodes.
510  *
511  * Returns a pointer to newly created objagg instance in case of success,
512  * otherwise it returns pointer error using ERR_PTR macro.
513  */
514 struct objagg *objagg_create(const struct objagg_ops *ops,
515                              struct objagg_hints *objagg_hints, void *priv)
516 {
517         struct objagg *objagg;
518         int err;
519 
520         if (WARN_ON(!ops || !ops->root_create || !ops->root_destroy ||
521                     !ops->delta_check || !ops->delta_create ||
522                     !ops->delta_destroy))
523                 return ERR_PTR(-EINVAL);
524 
525         objagg = kzalloc(sizeof(*objagg), GFP_KERNEL);
526         if (!objagg)
527                 return ERR_PTR(-ENOMEM);
528         objagg->ops = ops;
529         if (objagg_hints) {
530                 objagg->hints = objagg_hints;
531                 objagg_hints->refcount++;
532         }
533         objagg->priv = priv;
534         INIT_LIST_HEAD(&objagg->obj_list);
535 
536         objagg->ht_params.key_len = ops->obj_size;
537         objagg->ht_params.key_offset = offsetof(struct objagg_obj, obj);
538         objagg->ht_params.head_offset = offsetof(struct objagg_obj, ht_node);
539 
540         err = rhashtable_init(&objagg->obj_ht, &objagg->ht_params);
541         if (err)
542                 goto err_rhashtable_init;
543 
544         ida_init(&objagg->root_ida);
545 
546         trace_objagg_create(objagg);
547         return objagg;
548 
549 err_rhashtable_init:
550         kfree(objagg);
551         return ERR_PTR(err);
552 }
553 EXPORT_SYMBOL(objagg_create);
554 
555 /**
556  * objagg_destroy - destroys a new objagg instance
557  * @objagg:     objagg instance
558  *
559  * Note: all locking must be provided by the caller.
560  */
561 void objagg_destroy(struct objagg *objagg)
562 {
563         trace_objagg_destroy(objagg);
564         ida_destroy(&objagg->root_ida);
565         WARN_ON(!list_empty(&objagg->obj_list));
566         rhashtable_destroy(&objagg->obj_ht);
567         if (objagg->hints)
568                 objagg_hints_put(objagg->hints);
569         kfree(objagg);
570 }
571 EXPORT_SYMBOL(objagg_destroy);
572 
573 static int objagg_stats_info_sort_cmp_func(const void *a, const void *b)
574 {
575         const struct objagg_obj_stats_info *stats_info1 = a;
576         const struct objagg_obj_stats_info *stats_info2 = b;
577 
578         if (stats_info1->is_root != stats_info2->is_root)
579                 return stats_info2->is_root - stats_info1->is_root;
580         if (stats_info1->stats.delta_user_count !=
581             stats_info2->stats.delta_user_count)
582                 return stats_info2->stats.delta_user_count -
583                        stats_info1->stats.delta_user_count;
584         return stats_info2->stats.user_count - stats_info1->stats.user_count;
585 }
586 
587 /**
588  * objagg_stats_get - obtains stats of the objagg instance
589  * @objagg:     objagg instance
590  *
591  * Note: all locking must be provided by the caller.
592  *
593  * The returned structure contains statistics of all object
594  * currently in use, ordered by following rules:
595  * 1) Root objects are always on lower indexes than the rest.
596  * 2) Objects with higher delta user count are always on lower
597  *    indexes.
598  * 3) In case more objects have the same delta user count,
599  *    the objects are ordered by user count.
600  *
601  * Returns a pointer to stats instance in case of success,
602  * otherwise it returns pointer error using ERR_PTR macro.
603  */
604 const struct objagg_stats *objagg_stats_get(struct objagg *objagg)
605 {
606         struct objagg_stats *objagg_stats;
607         struct objagg_obj *objagg_obj;
608         int i;
609 
610         objagg_stats = kzalloc(struct_size(objagg_stats, stats_info,
611                                            objagg->obj_count), GFP_KERNEL);
612         if (!objagg_stats)
613                 return ERR_PTR(-ENOMEM);
614 
615         i = 0;
616         list_for_each_entry(objagg_obj, &objagg->obj_list, list) {
617                 memcpy(&objagg_stats->stats_info[i].stats, &objagg_obj->stats,
618                        sizeof(objagg_stats->stats_info[0].stats));
619                 objagg_stats->stats_info[i].objagg_obj = objagg_obj;
620                 objagg_stats->stats_info[i].is_root =
621                                         objagg_obj_is_root(objagg_obj);
622                 if (objagg_stats->stats_info[i].is_root)
623                         objagg_stats->root_count++;
624                 i++;
625         }
626         objagg_stats->stats_info_count = i;
627 
628         sort(objagg_stats->stats_info, objagg_stats->stats_info_count,
629              sizeof(struct objagg_obj_stats_info),
630              objagg_stats_info_sort_cmp_func, NULL);
631 
632         return objagg_stats;
633 }
634 EXPORT_SYMBOL(objagg_stats_get);
635 
636 /**
637  * objagg_stats_put - puts stats of the objagg instance
638  * @objagg_stats:       objagg instance stats
639  *
640  * Note: all locking must be provided by the caller.
641  */
642 void objagg_stats_put(const struct objagg_stats *objagg_stats)
643 {
644         kfree(objagg_stats);
645 }
646 EXPORT_SYMBOL(objagg_stats_put);
647 
648 static struct objagg_hints_node *
649 objagg_hints_node_create(struct objagg_hints *objagg_hints,
650                          struct objagg_obj *objagg_obj, size_t obj_size,
651                          struct objagg_hints_node *parent_hnode)
652 {
653         unsigned int user_count = objagg_obj->stats.user_count;
654         struct objagg_hints_node *hnode;
655         int err;
656 
657         hnode = kzalloc(sizeof(*hnode) + obj_size, GFP_KERNEL);
658         if (!hnode)
659                 return ERR_PTR(-ENOMEM);
660         memcpy(hnode->obj, &objagg_obj->obj, obj_size);
661         hnode->stats_info.stats.user_count = user_count;
662         hnode->stats_info.stats.delta_user_count = user_count;
663         if (parent_hnode) {
664                 parent_hnode->stats_info.stats.delta_user_count += user_count;
665         } else {
666                 hnode->root_id = objagg_hints->root_count++;
667                 hnode->stats_info.is_root = true;
668         }
669         hnode->stats_info.objagg_obj = objagg_obj;
670 
671         err = rhashtable_insert_fast(&objagg_hints->node_ht, &hnode->ht_node,
672                                      objagg_hints->ht_params);
673         if (err)
674                 goto err_ht_insert;
675 
676         list_add(&hnode->list, &objagg_hints->node_list);
677         hnode->parent = parent_hnode;
678         objagg_hints->node_count++;
679 
680         return hnode;
681 
682 err_ht_insert:
683         kfree(hnode);
684         return ERR_PTR(err);
685 }
686 
687 static void objagg_hints_flush(struct objagg_hints *objagg_hints)
688 {
689         struct objagg_hints_node *hnode, *tmp;
690 
691         list_for_each_entry_safe(hnode, tmp, &objagg_hints->node_list, list) {
692                 list_del(&hnode->list);
693                 rhashtable_remove_fast(&objagg_hints->node_ht, &hnode->ht_node,
694                                        objagg_hints->ht_params);
695                 kfree(hnode);
696         }
697 }
698 
699 struct objagg_tmp_node {
700         struct objagg_obj *objagg_obj;
701         bool crossed_out;
702 };
703 
704 struct objagg_tmp_graph {
705         struct objagg_tmp_node *nodes;
706         unsigned long nodes_count;
707         unsigned long *edges;
708 };
709 
710 static int objagg_tmp_graph_edge_index(struct objagg_tmp_graph *graph,
711                                        int parent_index, int index)
712 {
713         return index * graph->nodes_count + parent_index;
714 }
715 
716 static void objagg_tmp_graph_edge_set(struct objagg_tmp_graph *graph,
717                                       int parent_index, int index)
718 {
719         int edge_index = objagg_tmp_graph_edge_index(graph, index,
720                                                      parent_index);
721 
722         __set_bit(edge_index, graph->edges);
723 }
724 
725 static bool objagg_tmp_graph_is_edge(struct objagg_tmp_graph *graph,
726                                      int parent_index, int index)
727 {
728         int edge_index = objagg_tmp_graph_edge_index(graph, index,
729                                                      parent_index);
730 
731         return test_bit(edge_index, graph->edges);
732 }
733 
734 static unsigned int objagg_tmp_graph_node_weight(struct objagg_tmp_graph *graph,
735                                                  unsigned int index)
736 {
737         struct objagg_tmp_node *node = &graph->nodes[index];
738         unsigned int weight = node->objagg_obj->stats.user_count;
739         int j;
740 
741         /* Node weight is sum of node users and all other nodes users
742          * that this node can represent with delta.
743          */
744 
745         for (j = 0; j < graph->nodes_count; j++) {
746                 if (!objagg_tmp_graph_is_edge(graph, index, j))
747                         continue;
748                 node = &graph->nodes[j];
749                 if (node->crossed_out)
750                         continue;
751                 weight += node->objagg_obj->stats.user_count;
752         }
753         return weight;
754 }
755 
756 static int objagg_tmp_graph_node_max_weight(struct objagg_tmp_graph *graph)
757 {
758         struct objagg_tmp_node *node;
759         unsigned int max_weight = 0;
760         unsigned int weight;
761         int max_index = -1;
762         int i;
763 
764         for (i = 0; i < graph->nodes_count; i++) {
765                 node = &graph->nodes[i];
766                 if (node->crossed_out)
767                         continue;
768                 weight = objagg_tmp_graph_node_weight(graph, i);
769                 if (weight >= max_weight) {
770                         max_weight = weight;
771                         max_index = i;
772                 }
773         }
774         return max_index;
775 }
776 
777 static struct objagg_tmp_graph *objagg_tmp_graph_create(struct objagg *objagg)
778 {
779         unsigned int nodes_count = objagg->obj_count;
780         struct objagg_tmp_graph *graph;
781         struct objagg_tmp_node *node;
782         struct objagg_tmp_node *pnode;
783         struct objagg_obj *objagg_obj;
784         size_t alloc_size;
785         int i, j;
786 
787         graph = kzalloc(sizeof(*graph), GFP_KERNEL);
788         if (!graph)
789                 return NULL;
790 
791         graph->nodes = kcalloc(nodes_count, sizeof(*graph->nodes), GFP_KERNEL);
792         if (!graph->nodes)
793                 goto err_nodes_alloc;
794         graph->nodes_count = nodes_count;
795 
796         alloc_size = BITS_TO_LONGS(nodes_count * nodes_count) *
797                      sizeof(unsigned long);
798         graph->edges = kzalloc(alloc_size, GFP_KERNEL);
799         if (!graph->edges)
800                 goto err_edges_alloc;
801 
802         i = 0;
803         list_for_each_entry(objagg_obj, &objagg->obj_list, list) {
804                 node = &graph->nodes[i++];
805                 node->objagg_obj = objagg_obj;
806         }
807 
808         /* Assemble a temporary graph. Insert edge X->Y in case Y can be
809          * in delta of X.
810          */
811         for (i = 0; i < nodes_count; i++) {
812                 for (j = 0; j < nodes_count; j++) {
813                         if (i == j)
814                                 continue;
815                         pnode = &graph->nodes[i];
816                         node = &graph->nodes[j];
817                         if (objagg->ops->delta_check(objagg->priv,
818                                                      pnode->objagg_obj->obj,
819                                                      node->objagg_obj->obj)) {
820                                 objagg_tmp_graph_edge_set(graph, i, j);
821 
822                         }
823                 }
824         }
825         return graph;
826 
827 err_edges_alloc:
828         kfree(graph->nodes);
829 err_nodes_alloc:
830         kfree(graph);
831         return NULL;
832 }
833 
834 static void objagg_tmp_graph_destroy(struct objagg_tmp_graph *graph)
835 {
836         kfree(graph->edges);
837         kfree(graph->nodes);
838         kfree(graph);
839 }
840 
841 static int
842 objagg_opt_simple_greedy_fillup_hints(struct objagg_hints *objagg_hints,
843                                       struct objagg *objagg)
844 {
845         struct objagg_hints_node *hnode, *parent_hnode;
846         struct objagg_tmp_graph *graph;
847         struct objagg_tmp_node *node;
848         int index;
849         int j;
850         int err;
851 
852         graph = objagg_tmp_graph_create(objagg);
853         if (!graph)
854                 return -ENOMEM;
855 
856         /* Find the nodes from the ones that can accommodate most users
857          * and cross them out of the graph. Save them to the hint list.
858          */
859         while ((index = objagg_tmp_graph_node_max_weight(graph)) != -1) {
860                 node = &graph->nodes[index];
861                 node->crossed_out = true;
862                 hnode = objagg_hints_node_create(objagg_hints,
863                                                  node->objagg_obj,
864                                                  objagg->ops->obj_size,
865                                                  NULL);
866                 if (IS_ERR(hnode)) {
867                         err = PTR_ERR(hnode);
868                         goto out;
869                 }
870                 parent_hnode = hnode;
871                 for (j = 0; j < graph->nodes_count; j++) {
872                         if (!objagg_tmp_graph_is_edge(graph, index, j))
873                                 continue;
874                         node = &graph->nodes[j];
875                         if (node->crossed_out)
876                                 continue;
877                         node->crossed_out = true;
878                         hnode = objagg_hints_node_create(objagg_hints,
879                                                          node->objagg_obj,
880                                                          objagg->ops->obj_size,
881                                                          parent_hnode);
882                         if (IS_ERR(hnode)) {
883                                 err = PTR_ERR(hnode);
884                                 goto out;
885                         }
886                 }
887         }
888 
889         err = 0;
890 out:
891         objagg_tmp_graph_destroy(graph);
892         return err;
893 }
894 
895 struct objagg_opt_algo {
896         int (*fillup_hints)(struct objagg_hints *objagg_hints,
897                             struct objagg *objagg);
898 };
899 
900 static const struct objagg_opt_algo objagg_opt_simple_greedy = {
901         .fillup_hints = objagg_opt_simple_greedy_fillup_hints,
902 };
903 
904 
905 static const struct objagg_opt_algo *objagg_opt_algos[] = {
906         [OBJAGG_OPT_ALGO_SIMPLE_GREEDY] = &objagg_opt_simple_greedy,
907 };
908 
909 static int objagg_hints_obj_cmp(struct rhashtable_compare_arg *arg,
910                                 const void *obj)
911 {
912         struct rhashtable *ht = arg->ht;
913         struct objagg_hints *objagg_hints =
914                         container_of(ht, struct objagg_hints, node_ht);
915         const struct objagg_ops *ops = objagg_hints->ops;
916         const char *ptr = obj;
917 
918         ptr += ht->p.key_offset;
919         return ops->hints_obj_cmp ? ops->hints_obj_cmp(ptr, arg->key) :
920                                     memcmp(ptr, arg->key, ht->p.key_len);
921 }
922 
923 /**
924  * objagg_hints_get - obtains hints instance
925  * @objagg:             objagg instance
926  * @opt_algo_type:      type of hints finding algorithm
927  *
928  * Note: all locking must be provided by the caller.
929  *
930  * According to the algo type, the existing objects of objagg instance
931  * are going to be went-through to assemble an optimal tree. We call this
932  * tree hints. These hints can be later on used for creation of
933  * a new objagg instance. There, the future object creations are going
934  * to be consulted with these hints in order to find out, where exactly
935  * the new object should be put as a root or delta.
936  *
937  * Returns a pointer to hints instance in case of success,
938  * otherwise it returns pointer error using ERR_PTR macro.
939  */
940 struct objagg_hints *objagg_hints_get(struct objagg *objagg,
941                                       enum objagg_opt_algo_type opt_algo_type)
942 {
943         const struct objagg_opt_algo *algo = objagg_opt_algos[opt_algo_type];
944         struct objagg_hints *objagg_hints;
945         int err;
946 
947         objagg_hints = kzalloc(sizeof(*objagg_hints), GFP_KERNEL);
948         if (!objagg_hints)
949                 return ERR_PTR(-ENOMEM);
950 
951         objagg_hints->ops = objagg->ops;
952         objagg_hints->refcount = 1;
953 
954         INIT_LIST_HEAD(&objagg_hints->node_list);
955 
956         objagg_hints->ht_params.key_len = objagg->ops->obj_size;
957         objagg_hints->ht_params.key_offset =
958                                 offsetof(struct objagg_hints_node, obj);
959         objagg_hints->ht_params.head_offset =
960                                 offsetof(struct objagg_hints_node, ht_node);
961         objagg_hints->ht_params.obj_cmpfn = objagg_hints_obj_cmp;
962 
963         err = rhashtable_init(&objagg_hints->node_ht, &objagg_hints->ht_params);
964         if (err)
965                 goto err_rhashtable_init;
966 
967         err = algo->fillup_hints(objagg_hints, objagg);
968         if (err)
969                 goto err_fillup_hints;
970 
971         if (WARN_ON(objagg_hints->node_count != objagg->obj_count)) {
972                 err = -EINVAL;
973                 goto err_node_count_check;
974         }
975 
976         return objagg_hints;
977 
978 err_node_count_check:
979 err_fillup_hints:
980         objagg_hints_flush(objagg_hints);
981         rhashtable_destroy(&objagg_hints->node_ht);
982 err_rhashtable_init:
983         kfree(objagg_hints);
984         return ERR_PTR(err);
985 }
986 EXPORT_SYMBOL(objagg_hints_get);
987 
988 /**
989  * objagg_hints_put - puts hints instance
990  * @objagg_hints:       objagg hints instance
991  *
992  * Note: all locking must be provided by the caller.
993  */
994 void objagg_hints_put(struct objagg_hints *objagg_hints)
995 {
996         if (--objagg_hints->refcount)
997                 return;
998         objagg_hints_flush(objagg_hints);
999         rhashtable_destroy(&objagg_hints->node_ht);
1000         kfree(objagg_hints);
1001 }
1002 EXPORT_SYMBOL(objagg_hints_put);
1003 
1004 /**
1005  * objagg_hints_stats_get - obtains stats of the hints instance
1006  * @objagg_hints:       hints instance
1007  *
1008  * Note: all locking must be provided by the caller.
1009  *
1010  * The returned structure contains statistics of all objects
1011  * currently in use, ordered by following rules:
1012  * 1) Root objects are always on lower indexes than the rest.
1013  * 2) Objects with higher delta user count are always on lower
1014  *    indexes.
1015  * 3) In case multiple objects have the same delta user count,
1016  *    the objects are ordered by user count.
1017  *
1018  * Returns a pointer to stats instance in case of success,
1019  * otherwise it returns pointer error using ERR_PTR macro.
1020  */
1021 const struct objagg_stats *
1022 objagg_hints_stats_get(struct objagg_hints *objagg_hints)
1023 {
1024         struct objagg_stats *objagg_stats;
1025         struct objagg_hints_node *hnode;
1026         int i;
1027 
1028         objagg_stats = kzalloc(struct_size(objagg_stats, stats_info,
1029                                            objagg_hints->node_count),
1030                                GFP_KERNEL);
1031         if (!objagg_stats)
1032                 return ERR_PTR(-ENOMEM);
1033 
1034         i = 0;
1035         list_for_each_entry(hnode, &objagg_hints->node_list, list) {
1036                 memcpy(&objagg_stats->stats_info[i], &hnode->stats_info,
1037                        sizeof(objagg_stats->stats_info[0]));
1038                 if (objagg_stats->stats_info[i].is_root)
1039                         objagg_stats->root_count++;
1040                 i++;
1041         }
1042         objagg_stats->stats_info_count = i;
1043 
1044         sort(objagg_stats->stats_info, objagg_stats->stats_info_count,
1045              sizeof(struct objagg_obj_stats_info),
1046              objagg_stats_info_sort_cmp_func, NULL);
1047 
1048         return objagg_stats;
1049 }
1050 EXPORT_SYMBOL(objagg_hints_stats_get);
1051 
1052 MODULE_LICENSE("Dual BSD/GPL");
1053 MODULE_AUTHOR("Jiri Pirko <jiri@mellanox.com>");
1054 MODULE_DESCRIPTION("Object aggregation manager");
1055 

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