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TOMOYO Linux Cross Reference
Linux/lib/rhashtable.c

Version: ~ [ linux-5.1-rc1 ] ~ [ linux-5.0.3 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.30 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.107 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.164 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.176 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.136 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.63 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.39.4 ] ~ [ linux-2.6.38.8 ] ~ [ linux-2.6.37.6 ] ~ [ linux-2.6.36.4 ] ~ [ linux-2.6.35.14 ] ~ [ linux-2.6.34.15 ] ~ [ linux-2.6.33.20 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 /*
  2  * Resizable, Scalable, Concurrent Hash Table
  3  *
  4  * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>
  5  * Copyright (c) 2014-2015 Thomas Graf <tgraf@suug.ch>
  6  * Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net>
  7  *
  8  * Code partially derived from nft_hash
  9  * Rewritten with rehash code from br_multicast plus single list
 10  * pointer as suggested by Josh Triplett
 11  *
 12  * This program is free software; you can redistribute it and/or modify
 13  * it under the terms of the GNU General Public License version 2 as
 14  * published by the Free Software Foundation.
 15  */
 16 
 17 #include <linux/atomic.h>
 18 #include <linux/kernel.h>
 19 #include <linux/init.h>
 20 #include <linux/log2.h>
 21 #include <linux/sched.h>
 22 #include <linux/rculist.h>
 23 #include <linux/slab.h>
 24 #include <linux/vmalloc.h>
 25 #include <linux/mm.h>
 26 #include <linux/jhash.h>
 27 #include <linux/random.h>
 28 #include <linux/rhashtable.h>
 29 #include <linux/err.h>
 30 #include <linux/export.h>
 31 
 32 #define HASH_DEFAULT_SIZE       64UL
 33 #define HASH_MIN_SIZE           4U
 34 #define BUCKET_LOCKS_PER_CPU    32UL
 35 
 36 union nested_table {
 37         union nested_table __rcu *table;
 38         struct rhash_head __rcu *bucket;
 39 };
 40 
 41 static u32 head_hashfn(struct rhashtable *ht,
 42                        const struct bucket_table *tbl,
 43                        const struct rhash_head *he)
 44 {
 45         return rht_head_hashfn(ht, tbl, he, ht->p);
 46 }
 47 
 48 #ifdef CONFIG_PROVE_LOCKING
 49 #define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT))
 50 
 51 int lockdep_rht_mutex_is_held(struct rhashtable *ht)
 52 {
 53         return (debug_locks) ? lockdep_is_held(&ht->mutex) : 1;
 54 }
 55 EXPORT_SYMBOL_GPL(lockdep_rht_mutex_is_held);
 56 
 57 int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash)
 58 {
 59         spinlock_t *lock = rht_bucket_lock(tbl, hash);
 60 
 61         return (debug_locks) ? lockdep_is_held(lock) : 1;
 62 }
 63 EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held);
 64 #else
 65 #define ASSERT_RHT_MUTEX(HT)
 66 #endif
 67 
 68 static void nested_table_free(union nested_table *ntbl, unsigned int size)
 69 {
 70         const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
 71         const unsigned int len = 1 << shift;
 72         unsigned int i;
 73 
 74         ntbl = rcu_dereference_raw(ntbl->table);
 75         if (!ntbl)
 76                 return;
 77 
 78         if (size > len) {
 79                 size >>= shift;
 80                 for (i = 0; i < len; i++)
 81                         nested_table_free(ntbl + i, size);
 82         }
 83 
 84         kfree(ntbl);
 85 }
 86 
 87 static void nested_bucket_table_free(const struct bucket_table *tbl)
 88 {
 89         unsigned int size = tbl->size >> tbl->nest;
 90         unsigned int len = 1 << tbl->nest;
 91         union nested_table *ntbl;
 92         unsigned int i;
 93 
 94         ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
 95 
 96         for (i = 0; i < len; i++)
 97                 nested_table_free(ntbl + i, size);
 98 
 99         kfree(ntbl);
100 }
101 
102 static void bucket_table_free(const struct bucket_table *tbl)
103 {
104         if (tbl->nest)
105                 nested_bucket_table_free(tbl);
106 
107         free_bucket_spinlocks(tbl->locks);
108         kvfree(tbl);
109 }
110 
111 static void bucket_table_free_rcu(struct rcu_head *head)
112 {
113         bucket_table_free(container_of(head, struct bucket_table, rcu));
114 }
115 
116 static union nested_table *nested_table_alloc(struct rhashtable *ht,
117                                               union nested_table __rcu **prev,
118                                               unsigned int shifted,
119                                               unsigned int nhash)
120 {
121         union nested_table *ntbl;
122         int i;
123 
124         ntbl = rcu_dereference(*prev);
125         if (ntbl)
126                 return ntbl;
127 
128         ntbl = kzalloc(PAGE_SIZE, GFP_ATOMIC);
129 
130         if (ntbl && shifted) {
131                 for (i = 0; i < PAGE_SIZE / sizeof(ntbl[0].bucket); i++)
132                         INIT_RHT_NULLS_HEAD(ntbl[i].bucket, ht,
133                                             (i << shifted) | nhash);
134         }
135 
136         rcu_assign_pointer(*prev, ntbl);
137 
138         return ntbl;
139 }
140 
141 static struct bucket_table *nested_bucket_table_alloc(struct rhashtable *ht,
142                                                       size_t nbuckets,
143                                                       gfp_t gfp)
144 {
145         const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
146         struct bucket_table *tbl;
147         size_t size;
148 
149         if (nbuckets < (1 << (shift + 1)))
150                 return NULL;
151 
152         size = sizeof(*tbl) + sizeof(tbl->buckets[0]);
153 
154         tbl = kzalloc(size, gfp);
155         if (!tbl)
156                 return NULL;
157 
158         if (!nested_table_alloc(ht, (union nested_table __rcu **)tbl->buckets,
159                                 0, 0)) {
160                 kfree(tbl);
161                 return NULL;
162         }
163 
164         tbl->nest = (ilog2(nbuckets) - 1) % shift + 1;
165 
166         return tbl;
167 }
168 
169 static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
170                                                size_t nbuckets,
171                                                gfp_t gfp)
172 {
173         struct bucket_table *tbl = NULL;
174         size_t size, max_locks;
175         int i;
176 
177         size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]);
178         if (gfp != GFP_KERNEL)
179                 tbl = kzalloc(size, gfp | __GFP_NOWARN | __GFP_NORETRY);
180         else
181                 tbl = kvzalloc(size, gfp);
182 
183         size = nbuckets;
184 
185         if (tbl == NULL && gfp != GFP_KERNEL) {
186                 tbl = nested_bucket_table_alloc(ht, nbuckets, gfp);
187                 nbuckets = 0;
188         }
189         if (tbl == NULL)
190                 return NULL;
191 
192         tbl->size = size;
193 
194         max_locks = size >> 1;
195         if (tbl->nest)
196                 max_locks = min_t(size_t, max_locks, 1U << tbl->nest);
197 
198         if (alloc_bucket_spinlocks(&tbl->locks, &tbl->locks_mask, max_locks,
199                                    ht->p.locks_mul, gfp) < 0) {
200                 bucket_table_free(tbl);
201                 return NULL;
202         }
203 
204         INIT_LIST_HEAD(&tbl->walkers);
205 
206         tbl->hash_rnd = get_random_u32();
207 
208         for (i = 0; i < nbuckets; i++)
209                 INIT_RHT_NULLS_HEAD(tbl->buckets[i], ht, i);
210 
211         return tbl;
212 }
213 
214 static struct bucket_table *rhashtable_last_table(struct rhashtable *ht,
215                                                   struct bucket_table *tbl)
216 {
217         struct bucket_table *new_tbl;
218 
219         do {
220                 new_tbl = tbl;
221                 tbl = rht_dereference_rcu(tbl->future_tbl, ht);
222         } while (tbl);
223 
224         return new_tbl;
225 }
226 
227 static int rhashtable_rehash_one(struct rhashtable *ht, unsigned int old_hash)
228 {
229         struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
230         struct bucket_table *new_tbl = rhashtable_last_table(ht,
231                 rht_dereference_rcu(old_tbl->future_tbl, ht));
232         struct rhash_head __rcu **pprev = rht_bucket_var(old_tbl, old_hash);
233         int err = -EAGAIN;
234         struct rhash_head *head, *next, *entry;
235         spinlock_t *new_bucket_lock;
236         unsigned int new_hash;
237 
238         if (new_tbl->nest)
239                 goto out;
240 
241         err = -ENOENT;
242 
243         rht_for_each(entry, old_tbl, old_hash) {
244                 err = 0;
245                 next = rht_dereference_bucket(entry->next, old_tbl, old_hash);
246 
247                 if (rht_is_a_nulls(next))
248                         break;
249 
250                 pprev = &entry->next;
251         }
252 
253         if (err)
254                 goto out;
255 
256         new_hash = head_hashfn(ht, new_tbl, entry);
257 
258         new_bucket_lock = rht_bucket_lock(new_tbl, new_hash);
259 
260         spin_lock_nested(new_bucket_lock, SINGLE_DEPTH_NESTING);
261         head = rht_dereference_bucket(new_tbl->buckets[new_hash],
262                                       new_tbl, new_hash);
263 
264         RCU_INIT_POINTER(entry->next, head);
265 
266         rcu_assign_pointer(new_tbl->buckets[new_hash], entry);
267         spin_unlock(new_bucket_lock);
268 
269         rcu_assign_pointer(*pprev, next);
270 
271 out:
272         return err;
273 }
274 
275 static int rhashtable_rehash_chain(struct rhashtable *ht,
276                                     unsigned int old_hash)
277 {
278         struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
279         spinlock_t *old_bucket_lock;
280         int err;
281 
282         old_bucket_lock = rht_bucket_lock(old_tbl, old_hash);
283 
284         spin_lock_bh(old_bucket_lock);
285         while (!(err = rhashtable_rehash_one(ht, old_hash)))
286                 ;
287 
288         if (err == -ENOENT) {
289                 old_tbl->rehash++;
290                 err = 0;
291         }
292         spin_unlock_bh(old_bucket_lock);
293 
294         return err;
295 }
296 
297 static int rhashtable_rehash_attach(struct rhashtable *ht,
298                                     struct bucket_table *old_tbl,
299                                     struct bucket_table *new_tbl)
300 {
301         /* Protect future_tbl using the first bucket lock. */
302         spin_lock_bh(old_tbl->locks);
303 
304         /* Did somebody beat us to it? */
305         if (rcu_access_pointer(old_tbl->future_tbl)) {
306                 spin_unlock_bh(old_tbl->locks);
307                 return -EEXIST;
308         }
309 
310         /* Make insertions go into the new, empty table right away. Deletions
311          * and lookups will be attempted in both tables until we synchronize.
312          */
313         rcu_assign_pointer(old_tbl->future_tbl, new_tbl);
314 
315         spin_unlock_bh(old_tbl->locks);
316 
317         return 0;
318 }
319 
320 static int rhashtable_rehash_table(struct rhashtable *ht)
321 {
322         struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
323         struct bucket_table *new_tbl;
324         struct rhashtable_walker *walker;
325         unsigned int old_hash;
326         int err;
327 
328         new_tbl = rht_dereference(old_tbl->future_tbl, ht);
329         if (!new_tbl)
330                 return 0;
331 
332         for (old_hash = 0; old_hash < old_tbl->size; old_hash++) {
333                 err = rhashtable_rehash_chain(ht, old_hash);
334                 if (err)
335                         return err;
336         }
337 
338         /* Publish the new table pointer. */
339         rcu_assign_pointer(ht->tbl, new_tbl);
340 
341         spin_lock(&ht->lock);
342         list_for_each_entry(walker, &old_tbl->walkers, list)
343                 walker->tbl = NULL;
344         spin_unlock(&ht->lock);
345 
346         /* Wait for readers. All new readers will see the new
347          * table, and thus no references to the old table will
348          * remain.
349          */
350         call_rcu(&old_tbl->rcu, bucket_table_free_rcu);
351 
352         return rht_dereference(new_tbl->future_tbl, ht) ? -EAGAIN : 0;
353 }
354 
355 static int rhashtable_rehash_alloc(struct rhashtable *ht,
356                                    struct bucket_table *old_tbl,
357                                    unsigned int size)
358 {
359         struct bucket_table *new_tbl;
360         int err;
361 
362         ASSERT_RHT_MUTEX(ht);
363 
364         new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
365         if (new_tbl == NULL)
366                 return -ENOMEM;
367 
368         err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
369         if (err)
370                 bucket_table_free(new_tbl);
371 
372         return err;
373 }
374 
375 /**
376  * rhashtable_shrink - Shrink hash table while allowing concurrent lookups
377  * @ht:         the hash table to shrink
378  *
379  * This function shrinks the hash table to fit, i.e., the smallest
380  * size would not cause it to expand right away automatically.
381  *
382  * The caller must ensure that no concurrent resizing occurs by holding
383  * ht->mutex.
384  *
385  * The caller must ensure that no concurrent table mutations take place.
386  * It is however valid to have concurrent lookups if they are RCU protected.
387  *
388  * It is valid to have concurrent insertions and deletions protected by per
389  * bucket locks or concurrent RCU protected lookups and traversals.
390  */
391 static int rhashtable_shrink(struct rhashtable *ht)
392 {
393         struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
394         unsigned int nelems = atomic_read(&ht->nelems);
395         unsigned int size = 0;
396 
397         if (nelems)
398                 size = roundup_pow_of_two(nelems * 3 / 2);
399         if (size < ht->p.min_size)
400                 size = ht->p.min_size;
401 
402         if (old_tbl->size <= size)
403                 return 0;
404 
405         if (rht_dereference(old_tbl->future_tbl, ht))
406                 return -EEXIST;
407 
408         return rhashtable_rehash_alloc(ht, old_tbl, size);
409 }
410 
411 static void rht_deferred_worker(struct work_struct *work)
412 {
413         struct rhashtable *ht;
414         struct bucket_table *tbl;
415         int err = 0;
416 
417         ht = container_of(work, struct rhashtable, run_work);
418         mutex_lock(&ht->mutex);
419 
420         tbl = rht_dereference(ht->tbl, ht);
421         tbl = rhashtable_last_table(ht, tbl);
422 
423         if (rht_grow_above_75(ht, tbl))
424                 err = rhashtable_rehash_alloc(ht, tbl, tbl->size * 2);
425         else if (ht->p.automatic_shrinking && rht_shrink_below_30(ht, tbl))
426                 err = rhashtable_shrink(ht);
427         else if (tbl->nest)
428                 err = rhashtable_rehash_alloc(ht, tbl, tbl->size);
429 
430         if (!err)
431                 err = rhashtable_rehash_table(ht);
432 
433         mutex_unlock(&ht->mutex);
434 
435         if (err)
436                 schedule_work(&ht->run_work);
437 }
438 
439 static int rhashtable_insert_rehash(struct rhashtable *ht,
440                                     struct bucket_table *tbl)
441 {
442         struct bucket_table *old_tbl;
443         struct bucket_table *new_tbl;
444         unsigned int size;
445         int err;
446 
447         old_tbl = rht_dereference_rcu(ht->tbl, ht);
448 
449         size = tbl->size;
450 
451         err = -EBUSY;
452 
453         if (rht_grow_above_75(ht, tbl))
454                 size *= 2;
455         /* Do not schedule more than one rehash */
456         else if (old_tbl != tbl)
457                 goto fail;
458 
459         err = -ENOMEM;
460 
461         new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC);
462         if (new_tbl == NULL)
463                 goto fail;
464 
465         err = rhashtable_rehash_attach(ht, tbl, new_tbl);
466         if (err) {
467                 bucket_table_free(new_tbl);
468                 if (err == -EEXIST)
469                         err = 0;
470         } else
471                 schedule_work(&ht->run_work);
472 
473         return err;
474 
475 fail:
476         /* Do not fail the insert if someone else did a rehash. */
477         if (likely(rcu_dereference_raw(tbl->future_tbl)))
478                 return 0;
479 
480         /* Schedule async rehash to retry allocation in process context. */
481         if (err == -ENOMEM)
482                 schedule_work(&ht->run_work);
483 
484         return err;
485 }
486 
487 static void *rhashtable_lookup_one(struct rhashtable *ht,
488                                    struct bucket_table *tbl, unsigned int hash,
489                                    const void *key, struct rhash_head *obj)
490 {
491         struct rhashtable_compare_arg arg = {
492                 .ht = ht,
493                 .key = key,
494         };
495         struct rhash_head __rcu **pprev;
496         struct rhash_head *head;
497         int elasticity;
498 
499         elasticity = RHT_ELASTICITY;
500         pprev = rht_bucket_var(tbl, hash);
501         rht_for_each_continue(head, *pprev, tbl, hash) {
502                 struct rhlist_head *list;
503                 struct rhlist_head *plist;
504 
505                 elasticity--;
506                 if (!key ||
507                     (ht->p.obj_cmpfn ?
508                      ht->p.obj_cmpfn(&arg, rht_obj(ht, head)) :
509                      rhashtable_compare(&arg, rht_obj(ht, head)))) {
510                         pprev = &head->next;
511                         continue;
512                 }
513 
514                 if (!ht->rhlist)
515                         return rht_obj(ht, head);
516 
517                 list = container_of(obj, struct rhlist_head, rhead);
518                 plist = container_of(head, struct rhlist_head, rhead);
519 
520                 RCU_INIT_POINTER(list->next, plist);
521                 head = rht_dereference_bucket(head->next, tbl, hash);
522                 RCU_INIT_POINTER(list->rhead.next, head);
523                 rcu_assign_pointer(*pprev, obj);
524 
525                 return NULL;
526         }
527 
528         if (elasticity <= 0)
529                 return ERR_PTR(-EAGAIN);
530 
531         return ERR_PTR(-ENOENT);
532 }
533 
534 static struct bucket_table *rhashtable_insert_one(struct rhashtable *ht,
535                                                   struct bucket_table *tbl,
536                                                   unsigned int hash,
537                                                   struct rhash_head *obj,
538                                                   void *data)
539 {
540         struct rhash_head __rcu **pprev;
541         struct bucket_table *new_tbl;
542         struct rhash_head *head;
543 
544         if (!IS_ERR_OR_NULL(data))
545                 return ERR_PTR(-EEXIST);
546 
547         if (PTR_ERR(data) != -EAGAIN && PTR_ERR(data) != -ENOENT)
548                 return ERR_CAST(data);
549 
550         new_tbl = rcu_dereference(tbl->future_tbl);
551         if (new_tbl)
552                 return new_tbl;
553 
554         if (PTR_ERR(data) != -ENOENT)
555                 return ERR_CAST(data);
556 
557         if (unlikely(rht_grow_above_max(ht, tbl)))
558                 return ERR_PTR(-E2BIG);
559 
560         if (unlikely(rht_grow_above_100(ht, tbl)))
561                 return ERR_PTR(-EAGAIN);
562 
563         pprev = rht_bucket_insert(ht, tbl, hash);
564         if (!pprev)
565                 return ERR_PTR(-ENOMEM);
566 
567         head = rht_dereference_bucket(*pprev, tbl, hash);
568 
569         RCU_INIT_POINTER(obj->next, head);
570         if (ht->rhlist) {
571                 struct rhlist_head *list;
572 
573                 list = container_of(obj, struct rhlist_head, rhead);
574                 RCU_INIT_POINTER(list->next, NULL);
575         }
576 
577         rcu_assign_pointer(*pprev, obj);
578 
579         atomic_inc(&ht->nelems);
580         if (rht_grow_above_75(ht, tbl))
581                 schedule_work(&ht->run_work);
582 
583         return NULL;
584 }
585 
586 static void *rhashtable_try_insert(struct rhashtable *ht, const void *key,
587                                    struct rhash_head *obj)
588 {
589         struct bucket_table *new_tbl;
590         struct bucket_table *tbl;
591         unsigned int hash;
592         spinlock_t *lock;
593         void *data;
594 
595         tbl = rcu_dereference(ht->tbl);
596 
597         /* All insertions must grab the oldest table containing
598          * the hashed bucket that is yet to be rehashed.
599          */
600         for (;;) {
601                 hash = rht_head_hashfn(ht, tbl, obj, ht->p);
602                 lock = rht_bucket_lock(tbl, hash);
603                 spin_lock_bh(lock);
604 
605                 if (tbl->rehash <= hash)
606                         break;
607 
608                 spin_unlock_bh(lock);
609                 tbl = rcu_dereference(tbl->future_tbl);
610         }
611 
612         data = rhashtable_lookup_one(ht, tbl, hash, key, obj);
613         new_tbl = rhashtable_insert_one(ht, tbl, hash, obj, data);
614         if (PTR_ERR(new_tbl) != -EEXIST)
615                 data = ERR_CAST(new_tbl);
616 
617         while (!IS_ERR_OR_NULL(new_tbl)) {
618                 tbl = new_tbl;
619                 hash = rht_head_hashfn(ht, tbl, obj, ht->p);
620                 spin_lock_nested(rht_bucket_lock(tbl, hash),
621                                  SINGLE_DEPTH_NESTING);
622 
623                 data = rhashtable_lookup_one(ht, tbl, hash, key, obj);
624                 new_tbl = rhashtable_insert_one(ht, tbl, hash, obj, data);
625                 if (PTR_ERR(new_tbl) != -EEXIST)
626                         data = ERR_CAST(new_tbl);
627 
628                 spin_unlock(rht_bucket_lock(tbl, hash));
629         }
630 
631         spin_unlock_bh(lock);
632 
633         if (PTR_ERR(data) == -EAGAIN)
634                 data = ERR_PTR(rhashtable_insert_rehash(ht, tbl) ?:
635                                -EAGAIN);
636 
637         return data;
638 }
639 
640 void *rhashtable_insert_slow(struct rhashtable *ht, const void *key,
641                              struct rhash_head *obj)
642 {
643         void *data;
644 
645         do {
646                 rcu_read_lock();
647                 data = rhashtable_try_insert(ht, key, obj);
648                 rcu_read_unlock();
649         } while (PTR_ERR(data) == -EAGAIN);
650 
651         return data;
652 }
653 EXPORT_SYMBOL_GPL(rhashtable_insert_slow);
654 
655 /**
656  * rhashtable_walk_enter - Initialise an iterator
657  * @ht:         Table to walk over
658  * @iter:       Hash table Iterator
659  *
660  * This function prepares a hash table walk.
661  *
662  * Note that if you restart a walk after rhashtable_walk_stop you
663  * may see the same object twice.  Also, you may miss objects if
664  * there are removals in between rhashtable_walk_stop and the next
665  * call to rhashtable_walk_start.
666  *
667  * For a completely stable walk you should construct your own data
668  * structure outside the hash table.
669  *
670  * This function may sleep so you must not call it from interrupt
671  * context or with spin locks held.
672  *
673  * You must call rhashtable_walk_exit after this function returns.
674  */
675 void rhashtable_walk_enter(struct rhashtable *ht, struct rhashtable_iter *iter)
676 {
677         iter->ht = ht;
678         iter->p = NULL;
679         iter->slot = 0;
680         iter->skip = 0;
681         iter->end_of_table = 0;
682 
683         spin_lock(&ht->lock);
684         iter->walker.tbl =
685                 rcu_dereference_protected(ht->tbl, lockdep_is_held(&ht->lock));
686         list_add(&iter->walker.list, &iter->walker.tbl->walkers);
687         spin_unlock(&ht->lock);
688 }
689 EXPORT_SYMBOL_GPL(rhashtable_walk_enter);
690 
691 /**
692  * rhashtable_walk_exit - Free an iterator
693  * @iter:       Hash table Iterator
694  *
695  * This function frees resources allocated by rhashtable_walk_init.
696  */
697 void rhashtable_walk_exit(struct rhashtable_iter *iter)
698 {
699         spin_lock(&iter->ht->lock);
700         if (iter->walker.tbl)
701                 list_del(&iter->walker.list);
702         spin_unlock(&iter->ht->lock);
703 }
704 EXPORT_SYMBOL_GPL(rhashtable_walk_exit);
705 
706 /**
707  * rhashtable_walk_start_check - Start a hash table walk
708  * @iter:       Hash table iterator
709  *
710  * Start a hash table walk at the current iterator position.  Note that we take
711  * the RCU lock in all cases including when we return an error.  So you must
712  * always call rhashtable_walk_stop to clean up.
713  *
714  * Returns zero if successful.
715  *
716  * Returns -EAGAIN if resize event occured.  Note that the iterator
717  * will rewind back to the beginning and you may use it immediately
718  * by calling rhashtable_walk_next.
719  *
720  * rhashtable_walk_start is defined as an inline variant that returns
721  * void. This is preferred in cases where the caller would ignore
722  * resize events and always continue.
723  */
724 int rhashtable_walk_start_check(struct rhashtable_iter *iter)
725         __acquires(RCU)
726 {
727         struct rhashtable *ht = iter->ht;
728 
729         rcu_read_lock();
730 
731         spin_lock(&ht->lock);
732         if (iter->walker.tbl)
733                 list_del(&iter->walker.list);
734         spin_unlock(&ht->lock);
735 
736         if (!iter->walker.tbl && !iter->end_of_table) {
737                 iter->walker.tbl = rht_dereference_rcu(ht->tbl, ht);
738                 return -EAGAIN;
739         }
740 
741         return 0;
742 }
743 EXPORT_SYMBOL_GPL(rhashtable_walk_start_check);
744 
745 /**
746  * __rhashtable_walk_find_next - Find the next element in a table (or the first
747  * one in case of a new walk).
748  *
749  * @iter:       Hash table iterator
750  *
751  * Returns the found object or NULL when the end of the table is reached.
752  *
753  * Returns -EAGAIN if resize event occurred.
754  */
755 static void *__rhashtable_walk_find_next(struct rhashtable_iter *iter)
756 {
757         struct bucket_table *tbl = iter->walker.tbl;
758         struct rhlist_head *list = iter->list;
759         struct rhashtable *ht = iter->ht;
760         struct rhash_head *p = iter->p;
761         bool rhlist = ht->rhlist;
762 
763         if (!tbl)
764                 return NULL;
765 
766         for (; iter->slot < tbl->size; iter->slot++) {
767                 int skip = iter->skip;
768 
769                 rht_for_each_rcu(p, tbl, iter->slot) {
770                         if (rhlist) {
771                                 list = container_of(p, struct rhlist_head,
772                                                     rhead);
773                                 do {
774                                         if (!skip)
775                                                 goto next;
776                                         skip--;
777                                         list = rcu_dereference(list->next);
778                                 } while (list);
779 
780                                 continue;
781                         }
782                         if (!skip)
783                                 break;
784                         skip--;
785                 }
786 
787 next:
788                 if (!rht_is_a_nulls(p)) {
789                         iter->skip++;
790                         iter->p = p;
791                         iter->list = list;
792                         return rht_obj(ht, rhlist ? &list->rhead : p);
793                 }
794 
795                 iter->skip = 0;
796         }
797 
798         iter->p = NULL;
799 
800         /* Ensure we see any new tables. */
801         smp_rmb();
802 
803         iter->walker.tbl = rht_dereference_rcu(tbl->future_tbl, ht);
804         if (iter->walker.tbl) {
805                 iter->slot = 0;
806                 iter->skip = 0;
807                 return ERR_PTR(-EAGAIN);
808         } else {
809                 iter->end_of_table = true;
810         }
811 
812         return NULL;
813 }
814 
815 /**
816  * rhashtable_walk_next - Return the next object and advance the iterator
817  * @iter:       Hash table iterator
818  *
819  * Note that you must call rhashtable_walk_stop when you are finished
820  * with the walk.
821  *
822  * Returns the next object or NULL when the end of the table is reached.
823  *
824  * Returns -EAGAIN if resize event occurred.  Note that the iterator
825  * will rewind back to the beginning and you may continue to use it.
826  */
827 void *rhashtable_walk_next(struct rhashtable_iter *iter)
828 {
829         struct rhlist_head *list = iter->list;
830         struct rhashtable *ht = iter->ht;
831         struct rhash_head *p = iter->p;
832         bool rhlist = ht->rhlist;
833 
834         if (p) {
835                 if (!rhlist || !(list = rcu_dereference(list->next))) {
836                         p = rcu_dereference(p->next);
837                         list = container_of(p, struct rhlist_head, rhead);
838                 }
839                 if (!rht_is_a_nulls(p)) {
840                         iter->skip++;
841                         iter->p = p;
842                         iter->list = list;
843                         return rht_obj(ht, rhlist ? &list->rhead : p);
844                 }
845 
846                 /* At the end of this slot, switch to next one and then find
847                  * next entry from that point.
848                  */
849                 iter->skip = 0;
850                 iter->slot++;
851         }
852 
853         return __rhashtable_walk_find_next(iter);
854 }
855 EXPORT_SYMBOL_GPL(rhashtable_walk_next);
856 
857 /**
858  * rhashtable_walk_peek - Return the next object but don't advance the iterator
859  * @iter:       Hash table iterator
860  *
861  * Returns the next object or NULL when the end of the table is reached.
862  *
863  * Returns -EAGAIN if resize event occurred.  Note that the iterator
864  * will rewind back to the beginning and you may continue to use it.
865  */
866 void *rhashtable_walk_peek(struct rhashtable_iter *iter)
867 {
868         struct rhlist_head *list = iter->list;
869         struct rhashtable *ht = iter->ht;
870         struct rhash_head *p = iter->p;
871 
872         if (p)
873                 return rht_obj(ht, ht->rhlist ? &list->rhead : p);
874 
875         /* No object found in current iter, find next one in the table. */
876 
877         if (iter->skip) {
878                 /* A nonzero skip value points to the next entry in the table
879                  * beyond that last one that was found. Decrement skip so
880                  * we find the current value. __rhashtable_walk_find_next
881                  * will restore the original value of skip assuming that
882                  * the table hasn't changed.
883                  */
884                 iter->skip--;
885         }
886 
887         return __rhashtable_walk_find_next(iter);
888 }
889 EXPORT_SYMBOL_GPL(rhashtable_walk_peek);
890 
891 /**
892  * rhashtable_walk_stop - Finish a hash table walk
893  * @iter:       Hash table iterator
894  *
895  * Finish a hash table walk.  Does not reset the iterator to the start of the
896  * hash table.
897  */
898 void rhashtable_walk_stop(struct rhashtable_iter *iter)
899         __releases(RCU)
900 {
901         struct rhashtable *ht;
902         struct bucket_table *tbl = iter->walker.tbl;
903 
904         if (!tbl)
905                 goto out;
906 
907         ht = iter->ht;
908 
909         spin_lock(&ht->lock);
910         if (tbl->rehash < tbl->size)
911                 list_add(&iter->walker.list, &tbl->walkers);
912         else
913                 iter->walker.tbl = NULL;
914         spin_unlock(&ht->lock);
915 
916         iter->p = NULL;
917 
918 out:
919         rcu_read_unlock();
920 }
921 EXPORT_SYMBOL_GPL(rhashtable_walk_stop);
922 
923 static size_t rounded_hashtable_size(const struct rhashtable_params *params)
924 {
925         return max(roundup_pow_of_two(params->nelem_hint * 4 / 3),
926                    (unsigned long)params->min_size);
927 }
928 
929 static u32 rhashtable_jhash2(const void *key, u32 length, u32 seed)
930 {
931         return jhash2(key, length, seed);
932 }
933 
934 /**
935  * rhashtable_init - initialize a new hash table
936  * @ht:         hash table to be initialized
937  * @params:     configuration parameters
938  *
939  * Initializes a new hash table based on the provided configuration
940  * parameters. A table can be configured either with a variable or
941  * fixed length key:
942  *
943  * Configuration Example 1: Fixed length keys
944  * struct test_obj {
945  *      int                     key;
946  *      void *                  my_member;
947  *      struct rhash_head       node;
948  * };
949  *
950  * struct rhashtable_params params = {
951  *      .head_offset = offsetof(struct test_obj, node),
952  *      .key_offset = offsetof(struct test_obj, key),
953  *      .key_len = sizeof(int),
954  *      .hashfn = jhash,
955  *      .nulls_base = (1U << RHT_BASE_SHIFT),
956  * };
957  *
958  * Configuration Example 2: Variable length keys
959  * struct test_obj {
960  *      [...]
961  *      struct rhash_head       node;
962  * };
963  *
964  * u32 my_hash_fn(const void *data, u32 len, u32 seed)
965  * {
966  *      struct test_obj *obj = data;
967  *
968  *      return [... hash ...];
969  * }
970  *
971  * struct rhashtable_params params = {
972  *      .head_offset = offsetof(struct test_obj, node),
973  *      .hashfn = jhash,
974  *      .obj_hashfn = my_hash_fn,
975  * };
976  */
977 int rhashtable_init(struct rhashtable *ht,
978                     const struct rhashtable_params *params)
979 {
980         struct bucket_table *tbl;
981         size_t size;
982 
983         size = HASH_DEFAULT_SIZE;
984 
985         if ((!params->key_len && !params->obj_hashfn) ||
986             (params->obj_hashfn && !params->obj_cmpfn))
987                 return -EINVAL;
988 
989         if (params->nulls_base && params->nulls_base < (1U << RHT_BASE_SHIFT))
990                 return -EINVAL;
991 
992         memset(ht, 0, sizeof(*ht));
993         mutex_init(&ht->mutex);
994         spin_lock_init(&ht->lock);
995         memcpy(&ht->p, params, sizeof(*params));
996 
997         if (params->min_size)
998                 ht->p.min_size = roundup_pow_of_two(params->min_size);
999 
1000         /* Cap total entries at 2^31 to avoid nelems overflow. */
1001         ht->max_elems = 1u << 31;
1002 
1003         if (params->max_size) {
1004                 ht->p.max_size = rounddown_pow_of_two(params->max_size);
1005                 if (ht->p.max_size < ht->max_elems / 2)
1006                         ht->max_elems = ht->p.max_size * 2;
1007         }
1008 
1009         ht->p.min_size = max_t(u16, ht->p.min_size, HASH_MIN_SIZE);
1010 
1011         if (params->nelem_hint)
1012                 size = rounded_hashtable_size(&ht->p);
1013 
1014         if (params->locks_mul)
1015                 ht->p.locks_mul = roundup_pow_of_two(params->locks_mul);
1016         else
1017                 ht->p.locks_mul = BUCKET_LOCKS_PER_CPU;
1018 
1019         ht->key_len = ht->p.key_len;
1020         if (!params->hashfn) {
1021                 ht->p.hashfn = jhash;
1022 
1023                 if (!(ht->key_len & (sizeof(u32) - 1))) {
1024                         ht->key_len /= sizeof(u32);
1025                         ht->p.hashfn = rhashtable_jhash2;
1026                 }
1027         }
1028 
1029         tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
1030         if (tbl == NULL)
1031                 return -ENOMEM;
1032 
1033         atomic_set(&ht->nelems, 0);
1034 
1035         RCU_INIT_POINTER(ht->tbl, tbl);
1036 
1037         INIT_WORK(&ht->run_work, rht_deferred_worker);
1038 
1039         return 0;
1040 }
1041 EXPORT_SYMBOL_GPL(rhashtable_init);
1042 
1043 /**
1044  * rhltable_init - initialize a new hash list table
1045  * @hlt:        hash list table to be initialized
1046  * @params:     configuration parameters
1047  *
1048  * Initializes a new hash list table.
1049  *
1050  * See documentation for rhashtable_init.
1051  */
1052 int rhltable_init(struct rhltable *hlt, const struct rhashtable_params *params)
1053 {
1054         int err;
1055 
1056         /* No rhlist NULLs marking for now. */
1057         if (params->nulls_base)
1058                 return -EINVAL;
1059 
1060         err = rhashtable_init(&hlt->ht, params);
1061         hlt->ht.rhlist = true;
1062         return err;
1063 }
1064 EXPORT_SYMBOL_GPL(rhltable_init);
1065 
1066 static void rhashtable_free_one(struct rhashtable *ht, struct rhash_head *obj,
1067                                 void (*free_fn)(void *ptr, void *arg),
1068                                 void *arg)
1069 {
1070         struct rhlist_head *list;
1071 
1072         if (!ht->rhlist) {
1073                 free_fn(rht_obj(ht, obj), arg);
1074                 return;
1075         }
1076 
1077         list = container_of(obj, struct rhlist_head, rhead);
1078         do {
1079                 obj = &list->rhead;
1080                 list = rht_dereference(list->next, ht);
1081                 free_fn(rht_obj(ht, obj), arg);
1082         } while (list);
1083 }
1084 
1085 /**
1086  * rhashtable_free_and_destroy - free elements and destroy hash table
1087  * @ht:         the hash table to destroy
1088  * @free_fn:    callback to release resources of element
1089  * @arg:        pointer passed to free_fn
1090  *
1091  * Stops an eventual async resize. If defined, invokes free_fn for each
1092  * element to releasal resources. Please note that RCU protected
1093  * readers may still be accessing the elements. Releasing of resources
1094  * must occur in a compatible manner. Then frees the bucket array.
1095  *
1096  * This function will eventually sleep to wait for an async resize
1097  * to complete. The caller is responsible that no further write operations
1098  * occurs in parallel.
1099  */
1100 void rhashtable_free_and_destroy(struct rhashtable *ht,
1101                                  void (*free_fn)(void *ptr, void *arg),
1102                                  void *arg)
1103 {
1104         struct bucket_table *tbl;
1105         unsigned int i;
1106 
1107         cancel_work_sync(&ht->run_work);
1108 
1109         mutex_lock(&ht->mutex);
1110         tbl = rht_dereference(ht->tbl, ht);
1111         if (free_fn) {
1112                 for (i = 0; i < tbl->size; i++) {
1113                         struct rhash_head *pos, *next;
1114 
1115                         for (pos = rht_dereference(*rht_bucket(tbl, i), ht),
1116                              next = !rht_is_a_nulls(pos) ?
1117                                         rht_dereference(pos->next, ht) : NULL;
1118                              !rht_is_a_nulls(pos);
1119                              pos = next,
1120                              next = !rht_is_a_nulls(pos) ?
1121                                         rht_dereference(pos->next, ht) : NULL)
1122                                 rhashtable_free_one(ht, pos, free_fn, arg);
1123                 }
1124         }
1125 
1126         bucket_table_free(tbl);
1127         mutex_unlock(&ht->mutex);
1128 }
1129 EXPORT_SYMBOL_GPL(rhashtable_free_and_destroy);
1130 
1131 void rhashtable_destroy(struct rhashtable *ht)
1132 {
1133         return rhashtable_free_and_destroy(ht, NULL, NULL);
1134 }
1135 EXPORT_SYMBOL_GPL(rhashtable_destroy);
1136 
1137 struct rhash_head __rcu **rht_bucket_nested(const struct bucket_table *tbl,
1138                                             unsigned int hash)
1139 {
1140         const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
1141         static struct rhash_head __rcu *rhnull =
1142                 (struct rhash_head __rcu *)NULLS_MARKER(0);
1143         unsigned int index = hash & ((1 << tbl->nest) - 1);
1144         unsigned int size = tbl->size >> tbl->nest;
1145         unsigned int subhash = hash;
1146         union nested_table *ntbl;
1147 
1148         ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
1149         ntbl = rht_dereference_bucket_rcu(ntbl[index].table, tbl, hash);
1150         subhash >>= tbl->nest;
1151 
1152         while (ntbl && size > (1 << shift)) {
1153                 index = subhash & ((1 << shift) - 1);
1154                 ntbl = rht_dereference_bucket_rcu(ntbl[index].table,
1155                                                   tbl, hash);
1156                 size >>= shift;
1157                 subhash >>= shift;
1158         }
1159 
1160         if (!ntbl)
1161                 return &rhnull;
1162 
1163         return &ntbl[subhash].bucket;
1164 
1165 }
1166 EXPORT_SYMBOL_GPL(rht_bucket_nested);
1167 
1168 struct rhash_head __rcu **rht_bucket_nested_insert(struct rhashtable *ht,
1169                                                    struct bucket_table *tbl,
1170                                                    unsigned int hash)
1171 {
1172         const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
1173         unsigned int index = hash & ((1 << tbl->nest) - 1);
1174         unsigned int size = tbl->size >> tbl->nest;
1175         union nested_table *ntbl;
1176         unsigned int shifted;
1177         unsigned int nhash;
1178 
1179         ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
1180         hash >>= tbl->nest;
1181         nhash = index;
1182         shifted = tbl->nest;
1183         ntbl = nested_table_alloc(ht, &ntbl[index].table,
1184                                   size <= (1 << shift) ? shifted : 0, nhash);
1185 
1186         while (ntbl && size > (1 << shift)) {
1187                 index = hash & ((1 << shift) - 1);
1188                 size >>= shift;
1189                 hash >>= shift;
1190                 nhash |= index << shifted;
1191                 shifted += shift;
1192                 ntbl = nested_table_alloc(ht, &ntbl[index].table,
1193                                           size <= (1 << shift) ? shifted : 0,
1194                                           nhash);
1195         }
1196 
1197         if (!ntbl)
1198                 return NULL;
1199 
1200         return &ntbl[hash].bucket;
1201 
1202 }
1203 EXPORT_SYMBOL_GPL(rht_bucket_nested_insert);
1204 

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