xref: /openbmc/linux/include/linux/rhashtable.h (revision e47877c7)
1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3  * Resizable, Scalable, Concurrent Hash Table
4  *
5  * Copyright (c) 2015-2016 Herbert Xu <herbert@gondor.apana.org.au>
6  * Copyright (c) 2014-2015 Thomas Graf <tgraf@suug.ch>
7  * Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net>
8  *
9  * Code partially derived from nft_hash
10  * Rewritten with rehash code from br_multicast plus single list
11  * pointer as suggested by Josh Triplett
12  *
13  * This program is free software; you can redistribute it and/or modify
14  * it under the terms of the GNU General Public License version 2 as
15  * published by the Free Software Foundation.
16  */
17 
18 #ifndef _LINUX_RHASHTABLE_H
19 #define _LINUX_RHASHTABLE_H
20 
21 #include <linux/err.h>
22 #include <linux/errno.h>
23 #include <linux/jhash.h>
24 #include <linux/list_nulls.h>
25 #include <linux/workqueue.h>
26 #include <linux/rculist.h>
27 #include <linux/bit_spinlock.h>
28 
29 #include <linux/rhashtable-types.h>
30 /*
31  * Objects in an rhashtable have an embedded struct rhash_head
32  * which is linked into as hash chain from the hash table - or one
33  * of two or more hash tables when the rhashtable is being resized.
34  * The end of the chain is marked with a special nulls marks which has
35  * the least significant bit set but otherwise stores the address of
36  * the hash bucket.  This allows us to be sure we've found the end
37  * of the right list.
38  * The value stored in the hash bucket has BIT(0) used as a lock bit.
39  * This bit must be atomically set before any changes are made to
40  * the chain.  To avoid dereferencing this pointer without clearing
41  * the bit first, we use an opaque 'struct rhash_lock_head *' for the
42  * pointer stored in the bucket.  This struct needs to be defined so
43  * that rcu_dereference() works on it, but it has no content so a
44  * cast is needed for it to be useful.  This ensures it isn't
45  * used by mistake with clearing the lock bit first.
46  */
47 struct rhash_lock_head {};
48 
49 /* Maximum chain length before rehash
50  *
51  * The maximum (not average) chain length grows with the size of the hash
52  * table, at a rate of (log N)/(log log N).
53  *
54  * The value of 16 is selected so that even if the hash table grew to
55  * 2^32 you would not expect the maximum chain length to exceed it
56  * unless we are under attack (or extremely unlucky).
57  *
58  * As this limit is only to detect attacks, we don't need to set it to a
59  * lower value as you'd need the chain length to vastly exceed 16 to have
60  * any real effect on the system.
61  */
62 #define RHT_ELASTICITY	16u
63 
64 /**
65  * struct bucket_table - Table of hash buckets
66  * @size: Number of hash buckets
67  * @nest: Number of bits of first-level nested table.
68  * @rehash: Current bucket being rehashed
69  * @hash_rnd: Random seed to fold into hash
70  * @walkers: List of active walkers
71  * @rcu: RCU structure for freeing the table
72  * @future_tbl: Table under construction during rehashing
73  * @ntbl: Nested table used when out of memory.
74  * @buckets: size * hash buckets
75  */
76 struct bucket_table {
77 	unsigned int		size;
78 	unsigned int		nest;
79 	u32			hash_rnd;
80 	struct list_head	walkers;
81 	struct rcu_head		rcu;
82 
83 	struct bucket_table __rcu *future_tbl;
84 
85 	struct lockdep_map	dep_map;
86 
87 	struct rhash_lock_head __rcu *buckets[] ____cacheline_aligned_in_smp;
88 };
89 
90 /*
91  * NULLS_MARKER() expects a hash value with the low
92  * bits mostly likely to be significant, and it discards
93  * the msb.
94  * We give it an address, in which the bottom bit is
95  * always 0, and the msb might be significant.
96  * So we shift the address down one bit to align with
97  * expectations and avoid losing a significant bit.
98  *
99  * We never store the NULLS_MARKER in the hash table
100  * itself as we need the lsb for locking.
101  * Instead we store a NULL
102  */
103 #define	RHT_NULLS_MARKER(ptr)	\
104 	((void *)NULLS_MARKER(((unsigned long) (ptr)) >> 1))
105 #define INIT_RHT_NULLS_HEAD(ptr)	\
106 	((ptr) = NULL)
107 
rht_is_a_nulls(const struct rhash_head * ptr)108 static inline bool rht_is_a_nulls(const struct rhash_head *ptr)
109 {
110 	return ((unsigned long) ptr & 1);
111 }
112 
rht_obj(const struct rhashtable * ht,const struct rhash_head * he)113 static inline void *rht_obj(const struct rhashtable *ht,
114 			    const struct rhash_head *he)
115 {
116 	return (char *)he - ht->p.head_offset;
117 }
118 
rht_bucket_index(const struct bucket_table * tbl,unsigned int hash)119 static inline unsigned int rht_bucket_index(const struct bucket_table *tbl,
120 					    unsigned int hash)
121 {
122 	return hash & (tbl->size - 1);
123 }
124 
rht_key_get_hash(struct rhashtable * ht,const void * key,const struct rhashtable_params params,unsigned int hash_rnd)125 static inline unsigned int rht_key_get_hash(struct rhashtable *ht,
126 	const void *key, const struct rhashtable_params params,
127 	unsigned int hash_rnd)
128 {
129 	unsigned int hash;
130 
131 	/* params must be equal to ht->p if it isn't constant. */
132 	if (!__builtin_constant_p(params.key_len))
133 		hash = ht->p.hashfn(key, ht->key_len, hash_rnd);
134 	else if (params.key_len) {
135 		unsigned int key_len = params.key_len;
136 
137 		if (params.hashfn)
138 			hash = params.hashfn(key, key_len, hash_rnd);
139 		else if (key_len & (sizeof(u32) - 1))
140 			hash = jhash(key, key_len, hash_rnd);
141 		else
142 			hash = jhash2(key, key_len / sizeof(u32), hash_rnd);
143 	} else {
144 		unsigned int key_len = ht->p.key_len;
145 
146 		if (params.hashfn)
147 			hash = params.hashfn(key, key_len, hash_rnd);
148 		else
149 			hash = jhash(key, key_len, hash_rnd);
150 	}
151 
152 	return hash;
153 }
154 
rht_key_hashfn(struct rhashtable * ht,const struct bucket_table * tbl,const void * key,const struct rhashtable_params params)155 static inline unsigned int rht_key_hashfn(
156 	struct rhashtable *ht, const struct bucket_table *tbl,
157 	const void *key, const struct rhashtable_params params)
158 {
159 	unsigned int hash = rht_key_get_hash(ht, key, params, tbl->hash_rnd);
160 
161 	return rht_bucket_index(tbl, hash);
162 }
163 
rht_head_hashfn(struct rhashtable * ht,const struct bucket_table * tbl,const struct rhash_head * he,const struct rhashtable_params params)164 static inline unsigned int rht_head_hashfn(
165 	struct rhashtable *ht, const struct bucket_table *tbl,
166 	const struct rhash_head *he, const struct rhashtable_params params)
167 {
168 	const char *ptr = rht_obj(ht, he);
169 
170 	return likely(params.obj_hashfn) ?
171 	       rht_bucket_index(tbl, params.obj_hashfn(ptr, params.key_len ?:
172 							    ht->p.key_len,
173 						       tbl->hash_rnd)) :
174 	       rht_key_hashfn(ht, tbl, ptr + params.key_offset, params);
175 }
176 
177 /**
178  * rht_grow_above_75 - returns true if nelems > 0.75 * table-size
179  * @ht:		hash table
180  * @tbl:	current table
181  */
rht_grow_above_75(const struct rhashtable * ht,const struct bucket_table * tbl)182 static inline bool rht_grow_above_75(const struct rhashtable *ht,
183 				     const struct bucket_table *tbl)
184 {
185 	/* Expand table when exceeding 75% load */
186 	return atomic_read(&ht->nelems) > (tbl->size / 4 * 3) &&
187 	       (!ht->p.max_size || tbl->size < ht->p.max_size);
188 }
189 
190 /**
191  * rht_shrink_below_30 - returns true if nelems < 0.3 * table-size
192  * @ht:		hash table
193  * @tbl:	current table
194  */
rht_shrink_below_30(const struct rhashtable * ht,const struct bucket_table * tbl)195 static inline bool rht_shrink_below_30(const struct rhashtable *ht,
196 				       const struct bucket_table *tbl)
197 {
198 	/* Shrink table beneath 30% load */
199 	return atomic_read(&ht->nelems) < (tbl->size * 3 / 10) &&
200 	       tbl->size > ht->p.min_size;
201 }
202 
203 /**
204  * rht_grow_above_100 - returns true if nelems > table-size
205  * @ht:		hash table
206  * @tbl:	current table
207  */
rht_grow_above_100(const struct rhashtable * ht,const struct bucket_table * tbl)208 static inline bool rht_grow_above_100(const struct rhashtable *ht,
209 				      const struct bucket_table *tbl)
210 {
211 	return atomic_read(&ht->nelems) > tbl->size &&
212 		(!ht->p.max_size || tbl->size < ht->p.max_size);
213 }
214 
215 /**
216  * rht_grow_above_max - returns true if table is above maximum
217  * @ht:		hash table
218  * @tbl:	current table
219  */
rht_grow_above_max(const struct rhashtable * ht,const struct bucket_table * tbl)220 static inline bool rht_grow_above_max(const struct rhashtable *ht,
221 				      const struct bucket_table *tbl)
222 {
223 	return atomic_read(&ht->nelems) >= ht->max_elems;
224 }
225 
226 #ifdef CONFIG_PROVE_LOCKING
227 int lockdep_rht_mutex_is_held(struct rhashtable *ht);
228 int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash);
229 #else
lockdep_rht_mutex_is_held(struct rhashtable * ht)230 static inline int lockdep_rht_mutex_is_held(struct rhashtable *ht)
231 {
232 	return 1;
233 }
234 
lockdep_rht_bucket_is_held(const struct bucket_table * tbl,u32 hash)235 static inline int lockdep_rht_bucket_is_held(const struct bucket_table *tbl,
236 					     u32 hash)
237 {
238 	return 1;
239 }
240 #endif /* CONFIG_PROVE_LOCKING */
241 
242 void *rhashtable_insert_slow(struct rhashtable *ht, const void *key,
243 			     struct rhash_head *obj);
244 
245 void rhashtable_walk_enter(struct rhashtable *ht,
246 			   struct rhashtable_iter *iter);
247 void rhashtable_walk_exit(struct rhashtable_iter *iter);
248 int rhashtable_walk_start_check(struct rhashtable_iter *iter) __acquires(RCU);
249 
rhashtable_walk_start(struct rhashtable_iter * iter)250 static inline void rhashtable_walk_start(struct rhashtable_iter *iter)
251 {
252 	(void)rhashtable_walk_start_check(iter);
253 }
254 
255 void *rhashtable_walk_next(struct rhashtable_iter *iter);
256 void *rhashtable_walk_peek(struct rhashtable_iter *iter);
257 void rhashtable_walk_stop(struct rhashtable_iter *iter) __releases(RCU);
258 
259 void rhashtable_free_and_destroy(struct rhashtable *ht,
260 				 void (*free_fn)(void *ptr, void *arg),
261 				 void *arg);
262 void rhashtable_destroy(struct rhashtable *ht);
263 
264 struct rhash_lock_head __rcu **rht_bucket_nested(
265 	const struct bucket_table *tbl, unsigned int hash);
266 struct rhash_lock_head __rcu **__rht_bucket_nested(
267 	const struct bucket_table *tbl, unsigned int hash);
268 struct rhash_lock_head __rcu **rht_bucket_nested_insert(
269 	struct rhashtable *ht, struct bucket_table *tbl, unsigned int hash);
270 
271 #define rht_dereference(p, ht) \
272 	rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht))
273 
274 #define rht_dereference_rcu(p, ht) \
275 	rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht))
276 
277 #define rht_dereference_bucket(p, tbl, hash) \
278 	rcu_dereference_protected(p, lockdep_rht_bucket_is_held(tbl, hash))
279 
280 #define rht_dereference_bucket_rcu(p, tbl, hash) \
281 	rcu_dereference_check(p, lockdep_rht_bucket_is_held(tbl, hash))
282 
283 #define rht_entry(tpos, pos, member) \
284 	({ tpos = container_of(pos, typeof(*tpos), member); 1; })
285 
rht_bucket(const struct bucket_table * tbl,unsigned int hash)286 static inline struct rhash_lock_head __rcu *const *rht_bucket(
287 	const struct bucket_table *tbl, unsigned int hash)
288 {
289 	return unlikely(tbl->nest) ? rht_bucket_nested(tbl, hash) :
290 				     &tbl->buckets[hash];
291 }
292 
rht_bucket_var(struct bucket_table * tbl,unsigned int hash)293 static inline struct rhash_lock_head __rcu **rht_bucket_var(
294 	struct bucket_table *tbl, unsigned int hash)
295 {
296 	return unlikely(tbl->nest) ? __rht_bucket_nested(tbl, hash) :
297 				     &tbl->buckets[hash];
298 }
299 
rht_bucket_insert(struct rhashtable * ht,struct bucket_table * tbl,unsigned int hash)300 static inline struct rhash_lock_head __rcu **rht_bucket_insert(
301 	struct rhashtable *ht, struct bucket_table *tbl, unsigned int hash)
302 {
303 	return unlikely(tbl->nest) ? rht_bucket_nested_insert(ht, tbl, hash) :
304 				     &tbl->buckets[hash];
305 }
306 
307 /*
308  * We lock a bucket by setting BIT(0) in the pointer - this is always
309  * zero in real pointers.  The NULLS mark is never stored in the bucket,
310  * rather we store NULL if the bucket is empty.
311  * bit_spin_locks do not handle contention well, but the whole point
312  * of the hashtable design is to achieve minimum per-bucket contention.
313  * A nested hash table might not have a bucket pointer.  In that case
314  * we cannot get a lock.  For remove and replace the bucket cannot be
315  * interesting and doesn't need locking.
316  * For insert we allocate the bucket if this is the last bucket_table,
317  * and then take the lock.
318  * Sometimes we unlock a bucket by writing a new pointer there.  In that
319  * case we don't need to unlock, but we do need to reset state such as
320  * local_bh. For that we have rht_assign_unlock().  As rcu_assign_pointer()
321  * provides the same release semantics that bit_spin_unlock() provides,
322  * this is safe.
323  * When we write to a bucket without unlocking, we use rht_assign_locked().
324  */
325 
rht_lock(struct bucket_table * tbl,struct rhash_lock_head __rcu ** bkt)326 static inline unsigned long rht_lock(struct bucket_table *tbl,
327 				     struct rhash_lock_head __rcu **bkt)
328 {
329 	unsigned long flags;
330 
331 	local_irq_save(flags);
332 	bit_spin_lock(0, (unsigned long *)bkt);
333 	lock_map_acquire(&tbl->dep_map);
334 	return flags;
335 }
336 
rht_lock_nested(struct bucket_table * tbl,struct rhash_lock_head __rcu ** bucket,unsigned int subclass)337 static inline unsigned long rht_lock_nested(struct bucket_table *tbl,
338 					struct rhash_lock_head __rcu **bucket,
339 					unsigned int subclass)
340 {
341 	unsigned long flags;
342 
343 	local_irq_save(flags);
344 	bit_spin_lock(0, (unsigned long *)bucket);
345 	lock_acquire_exclusive(&tbl->dep_map, subclass, 0, NULL, _THIS_IP_);
346 	return flags;
347 }
348 
rht_unlock(struct bucket_table * tbl,struct rhash_lock_head __rcu ** bkt,unsigned long flags)349 static inline void rht_unlock(struct bucket_table *tbl,
350 			      struct rhash_lock_head __rcu **bkt,
351 			      unsigned long flags)
352 {
353 	lock_map_release(&tbl->dep_map);
354 	bit_spin_unlock(0, (unsigned long *)bkt);
355 	local_irq_restore(flags);
356 }
357 
__rht_ptr(struct rhash_lock_head * p,struct rhash_lock_head __rcu * const * bkt)358 static inline struct rhash_head *__rht_ptr(
359 	struct rhash_lock_head *p, struct rhash_lock_head __rcu *const *bkt)
360 {
361 	return (struct rhash_head *)
362 		((unsigned long)p & ~BIT(0) ?:
363 		 (unsigned long)RHT_NULLS_MARKER(bkt));
364 }
365 
366 /*
367  * Where 'bkt' is a bucket and might be locked:
368  *   rht_ptr_rcu() dereferences that pointer and clears the lock bit.
369  *   rht_ptr() dereferences in a context where the bucket is locked.
370  *   rht_ptr_exclusive() dereferences in a context where exclusive
371  *            access is guaranteed, such as when destroying the table.
372  */
rht_ptr_rcu(struct rhash_lock_head __rcu * const * bkt)373 static inline struct rhash_head *rht_ptr_rcu(
374 	struct rhash_lock_head __rcu *const *bkt)
375 {
376 	return __rht_ptr(rcu_dereference(*bkt), bkt);
377 }
378 
rht_ptr(struct rhash_lock_head __rcu * const * bkt,struct bucket_table * tbl,unsigned int hash)379 static inline struct rhash_head *rht_ptr(
380 	struct rhash_lock_head __rcu *const *bkt,
381 	struct bucket_table *tbl,
382 	unsigned int hash)
383 {
384 	return __rht_ptr(rht_dereference_bucket(*bkt, tbl, hash), bkt);
385 }
386 
rht_ptr_exclusive(struct rhash_lock_head __rcu * const * bkt)387 static inline struct rhash_head *rht_ptr_exclusive(
388 	struct rhash_lock_head __rcu *const *bkt)
389 {
390 	return __rht_ptr(rcu_dereference_protected(*bkt, 1), bkt);
391 }
392 
rht_assign_locked(struct rhash_lock_head __rcu ** bkt,struct rhash_head * obj)393 static inline void rht_assign_locked(struct rhash_lock_head __rcu **bkt,
394 				     struct rhash_head *obj)
395 {
396 	if (rht_is_a_nulls(obj))
397 		obj = NULL;
398 	rcu_assign_pointer(*bkt, (void *)((unsigned long)obj | BIT(0)));
399 }
400 
rht_assign_unlock(struct bucket_table * tbl,struct rhash_lock_head __rcu ** bkt,struct rhash_head * obj,unsigned long flags)401 static inline void rht_assign_unlock(struct bucket_table *tbl,
402 				     struct rhash_lock_head __rcu **bkt,
403 				     struct rhash_head *obj,
404 				     unsigned long flags)
405 {
406 	if (rht_is_a_nulls(obj))
407 		obj = NULL;
408 	lock_map_release(&tbl->dep_map);
409 	rcu_assign_pointer(*bkt, (void *)obj);
410 	preempt_enable();
411 	__release(bitlock);
412 	local_irq_restore(flags);
413 }
414 
415 /**
416  * rht_for_each_from - iterate over hash chain from given head
417  * @pos:	the &struct rhash_head to use as a loop cursor.
418  * @head:	the &struct rhash_head to start from
419  * @tbl:	the &struct bucket_table
420  * @hash:	the hash value / bucket index
421  */
422 #define rht_for_each_from(pos, head, tbl, hash) \
423 	for (pos = head;			\
424 	     !rht_is_a_nulls(pos);		\
425 	     pos = rht_dereference_bucket((pos)->next, tbl, hash))
426 
427 /**
428  * rht_for_each - iterate over hash chain
429  * @pos:	the &struct rhash_head to use as a loop cursor.
430  * @tbl:	the &struct bucket_table
431  * @hash:	the hash value / bucket index
432  */
433 #define rht_for_each(pos, tbl, hash) \
434 	rht_for_each_from(pos, rht_ptr(rht_bucket(tbl, hash), tbl, hash),  \
435 			  tbl, hash)
436 
437 /**
438  * rht_for_each_entry_from - iterate over hash chain from given head
439  * @tpos:	the type * to use as a loop cursor.
440  * @pos:	the &struct rhash_head to use as a loop cursor.
441  * @head:	the &struct rhash_head to start from
442  * @tbl:	the &struct bucket_table
443  * @hash:	the hash value / bucket index
444  * @member:	name of the &struct rhash_head within the hashable struct.
445  */
446 #define rht_for_each_entry_from(tpos, pos, head, tbl, hash, member)	\
447 	for (pos = head;						\
448 	     (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member);	\
449 	     pos = rht_dereference_bucket((pos)->next, tbl, hash))
450 
451 /**
452  * rht_for_each_entry - iterate over hash chain of given type
453  * @tpos:	the type * to use as a loop cursor.
454  * @pos:	the &struct rhash_head to use as a loop cursor.
455  * @tbl:	the &struct bucket_table
456  * @hash:	the hash value / bucket index
457  * @member:	name of the &struct rhash_head within the hashable struct.
458  */
459 #define rht_for_each_entry(tpos, pos, tbl, hash, member)		\
460 	rht_for_each_entry_from(tpos, pos,				\
461 				rht_ptr(rht_bucket(tbl, hash), tbl, hash), \
462 				tbl, hash, member)
463 
464 /**
465  * rht_for_each_entry_safe - safely iterate over hash chain of given type
466  * @tpos:	the type * to use as a loop cursor.
467  * @pos:	the &struct rhash_head to use as a loop cursor.
468  * @next:	the &struct rhash_head to use as next in loop cursor.
469  * @tbl:	the &struct bucket_table
470  * @hash:	the hash value / bucket index
471  * @member:	name of the &struct rhash_head within the hashable struct.
472  *
473  * This hash chain list-traversal primitive allows for the looped code to
474  * remove the loop cursor from the list.
475  */
476 #define rht_for_each_entry_safe(tpos, pos, next, tbl, hash, member)	      \
477 	for (pos = rht_ptr(rht_bucket(tbl, hash), tbl, hash),		      \
478 	     next = !rht_is_a_nulls(pos) ?				      \
479 		       rht_dereference_bucket(pos->next, tbl, hash) : NULL;   \
480 	     (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member);	      \
481 	     pos = next,						      \
482 	     next = !rht_is_a_nulls(pos) ?				      \
483 		       rht_dereference_bucket(pos->next, tbl, hash) : NULL)
484 
485 /**
486  * rht_for_each_rcu_from - iterate over rcu hash chain from given head
487  * @pos:	the &struct rhash_head to use as a loop cursor.
488  * @head:	the &struct rhash_head to start from
489  * @tbl:	the &struct bucket_table
490  * @hash:	the hash value / bucket index
491  *
492  * This hash chain list-traversal primitive may safely run concurrently with
493  * the _rcu mutation primitives such as rhashtable_insert() as long as the
494  * traversal is guarded by rcu_read_lock().
495  */
496 #define rht_for_each_rcu_from(pos, head, tbl, hash)			\
497 	for (({barrier(); }),						\
498 	     pos = head;						\
499 	     !rht_is_a_nulls(pos);					\
500 	     pos = rcu_dereference_raw(pos->next))
501 
502 /**
503  * rht_for_each_rcu - iterate over rcu hash chain
504  * @pos:	the &struct rhash_head to use as a loop cursor.
505  * @tbl:	the &struct bucket_table
506  * @hash:	the hash value / bucket index
507  *
508  * This hash chain list-traversal primitive may safely run concurrently with
509  * the _rcu mutation primitives such as rhashtable_insert() as long as the
510  * traversal is guarded by rcu_read_lock().
511  */
512 #define rht_for_each_rcu(pos, tbl, hash)			\
513 	for (({barrier(); }),					\
514 	     pos = rht_ptr_rcu(rht_bucket(tbl, hash));		\
515 	     !rht_is_a_nulls(pos);				\
516 	     pos = rcu_dereference_raw(pos->next))
517 
518 /**
519  * rht_for_each_entry_rcu_from - iterated over rcu hash chain from given head
520  * @tpos:	the type * to use as a loop cursor.
521  * @pos:	the &struct rhash_head to use as a loop cursor.
522  * @head:	the &struct rhash_head to start from
523  * @tbl:	the &struct bucket_table
524  * @hash:	the hash value / bucket index
525  * @member:	name of the &struct rhash_head within the hashable struct.
526  *
527  * This hash chain list-traversal primitive may safely run concurrently with
528  * the _rcu mutation primitives such as rhashtable_insert() as long as the
529  * traversal is guarded by rcu_read_lock().
530  */
531 #define rht_for_each_entry_rcu_from(tpos, pos, head, tbl, hash, member) \
532 	for (({barrier(); }),						    \
533 	     pos = head;						    \
534 	     (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member);	    \
535 	     pos = rht_dereference_bucket_rcu(pos->next, tbl, hash))
536 
537 /**
538  * rht_for_each_entry_rcu - iterate over rcu hash chain of given type
539  * @tpos:	the type * to use as a loop cursor.
540  * @pos:	the &struct rhash_head to use as a loop cursor.
541  * @tbl:	the &struct bucket_table
542  * @hash:	the hash value / bucket index
543  * @member:	name of the &struct rhash_head within the hashable struct.
544  *
545  * This hash chain list-traversal primitive may safely run concurrently with
546  * the _rcu mutation primitives such as rhashtable_insert() as long as the
547  * traversal is guarded by rcu_read_lock().
548  */
549 #define rht_for_each_entry_rcu(tpos, pos, tbl, hash, member)		   \
550 	rht_for_each_entry_rcu_from(tpos, pos,				   \
551 				    rht_ptr_rcu(rht_bucket(tbl, hash)),	   \
552 				    tbl, hash, member)
553 
554 /**
555  * rhl_for_each_rcu - iterate over rcu hash table list
556  * @pos:	the &struct rlist_head to use as a loop cursor.
557  * @list:	the head of the list
558  *
559  * This hash chain list-traversal primitive should be used on the
560  * list returned by rhltable_lookup.
561  */
562 #define rhl_for_each_rcu(pos, list)					\
563 	for (pos = list; pos; pos = rcu_dereference_raw(pos->next))
564 
565 /**
566  * rhl_for_each_entry_rcu - iterate over rcu hash table list of given type
567  * @tpos:	the type * to use as a loop cursor.
568  * @pos:	the &struct rlist_head to use as a loop cursor.
569  * @list:	the head of the list
570  * @member:	name of the &struct rlist_head within the hashable struct.
571  *
572  * This hash chain list-traversal primitive should be used on the
573  * list returned by rhltable_lookup.
574  */
575 #define rhl_for_each_entry_rcu(tpos, pos, list, member)			\
576 	for (pos = list; pos && rht_entry(tpos, pos, member);		\
577 	     pos = rcu_dereference_raw(pos->next))
578 
rhashtable_compare(struct rhashtable_compare_arg * arg,const void * obj)579 static inline int rhashtable_compare(struct rhashtable_compare_arg *arg,
580 				     const void *obj)
581 {
582 	struct rhashtable *ht = arg->ht;
583 	const char *ptr = obj;
584 
585 	return memcmp(ptr + ht->p.key_offset, arg->key, ht->p.key_len);
586 }
587 
588 /* Internal function, do not use. */
__rhashtable_lookup(struct rhashtable * ht,const void * key,const struct rhashtable_params params)589 static inline struct rhash_head *__rhashtable_lookup(
590 	struct rhashtable *ht, const void *key,
591 	const struct rhashtable_params params)
592 {
593 	struct rhashtable_compare_arg arg = {
594 		.ht = ht,
595 		.key = key,
596 	};
597 	struct rhash_lock_head __rcu *const *bkt;
598 	struct bucket_table *tbl;
599 	struct rhash_head *he;
600 	unsigned int hash;
601 
602 	tbl = rht_dereference_rcu(ht->tbl, ht);
603 restart:
604 	hash = rht_key_hashfn(ht, tbl, key, params);
605 	bkt = rht_bucket(tbl, hash);
606 	do {
607 		rht_for_each_rcu_from(he, rht_ptr_rcu(bkt), tbl, hash) {
608 			if (params.obj_cmpfn ?
609 			    params.obj_cmpfn(&arg, rht_obj(ht, he)) :
610 			    rhashtable_compare(&arg, rht_obj(ht, he)))
611 				continue;
612 			return he;
613 		}
614 		/* An object might have been moved to a different hash chain,
615 		 * while we walk along it - better check and retry.
616 		 */
617 	} while (he != RHT_NULLS_MARKER(bkt));
618 
619 	/* Ensure we see any new tables. */
620 	smp_rmb();
621 
622 	tbl = rht_dereference_rcu(tbl->future_tbl, ht);
623 	if (unlikely(tbl))
624 		goto restart;
625 
626 	return NULL;
627 }
628 
629 /**
630  * rhashtable_lookup - search hash table
631  * @ht:		hash table
632  * @key:	the pointer to the key
633  * @params:	hash table parameters
634  *
635  * Computes the hash value for the key and traverses the bucket chain looking
636  * for a entry with an identical key. The first matching entry is returned.
637  *
638  * This must only be called under the RCU read lock.
639  *
640  * Returns the first entry on which the compare function returned true.
641  */
rhashtable_lookup(struct rhashtable * ht,const void * key,const struct rhashtable_params params)642 static inline void *rhashtable_lookup(
643 	struct rhashtable *ht, const void *key,
644 	const struct rhashtable_params params)
645 {
646 	struct rhash_head *he = __rhashtable_lookup(ht, key, params);
647 
648 	return he ? rht_obj(ht, he) : NULL;
649 }
650 
651 /**
652  * rhashtable_lookup_fast - search hash table, without RCU read lock
653  * @ht:		hash table
654  * @key:	the pointer to the key
655  * @params:	hash table parameters
656  *
657  * Computes the hash value for the key and traverses the bucket chain looking
658  * for a entry with an identical key. The first matching entry is returned.
659  *
660  * Only use this function when you have other mechanisms guaranteeing
661  * that the object won't go away after the RCU read lock is released.
662  *
663  * Returns the first entry on which the compare function returned true.
664  */
rhashtable_lookup_fast(struct rhashtable * ht,const void * key,const struct rhashtable_params params)665 static inline void *rhashtable_lookup_fast(
666 	struct rhashtable *ht, const void *key,
667 	const struct rhashtable_params params)
668 {
669 	void *obj;
670 
671 	rcu_read_lock();
672 	obj = rhashtable_lookup(ht, key, params);
673 	rcu_read_unlock();
674 
675 	return obj;
676 }
677 
678 /**
679  * rhltable_lookup - search hash list table
680  * @hlt:	hash table
681  * @key:	the pointer to the key
682  * @params:	hash table parameters
683  *
684  * Computes the hash value for the key and traverses the bucket chain looking
685  * for a entry with an identical key.  All matching entries are returned
686  * in a list.
687  *
688  * This must only be called under the RCU read lock.
689  *
690  * Returns the list of entries that match the given key.
691  */
rhltable_lookup(struct rhltable * hlt,const void * key,const struct rhashtable_params params)692 static inline struct rhlist_head *rhltable_lookup(
693 	struct rhltable *hlt, const void *key,
694 	const struct rhashtable_params params)
695 {
696 	struct rhash_head *he = __rhashtable_lookup(&hlt->ht, key, params);
697 
698 	return he ? container_of(he, struct rhlist_head, rhead) : NULL;
699 }
700 
701 /* Internal function, please use rhashtable_insert_fast() instead. This
702  * function returns the existing element already in hashes in there is a clash,
703  * otherwise it returns an error via ERR_PTR().
704  */
__rhashtable_insert_fast(struct rhashtable * ht,const void * key,struct rhash_head * obj,const struct rhashtable_params params,bool rhlist)705 static inline void *__rhashtable_insert_fast(
706 	struct rhashtable *ht, const void *key, struct rhash_head *obj,
707 	const struct rhashtable_params params, bool rhlist)
708 {
709 	struct rhashtable_compare_arg arg = {
710 		.ht = ht,
711 		.key = key,
712 	};
713 	struct rhash_lock_head __rcu **bkt;
714 	struct rhash_head __rcu **pprev;
715 	struct bucket_table *tbl;
716 	struct rhash_head *head;
717 	unsigned long flags;
718 	unsigned int hash;
719 	int elasticity;
720 	void *data;
721 
722 	rcu_read_lock();
723 
724 	tbl = rht_dereference_rcu(ht->tbl, ht);
725 	hash = rht_head_hashfn(ht, tbl, obj, params);
726 	elasticity = RHT_ELASTICITY;
727 	bkt = rht_bucket_insert(ht, tbl, hash);
728 	data = ERR_PTR(-ENOMEM);
729 	if (!bkt)
730 		goto out;
731 	pprev = NULL;
732 	flags = rht_lock(tbl, bkt);
733 
734 	if (unlikely(rcu_access_pointer(tbl->future_tbl))) {
735 slow_path:
736 		rht_unlock(tbl, bkt, flags);
737 		rcu_read_unlock();
738 		return rhashtable_insert_slow(ht, key, obj);
739 	}
740 
741 	rht_for_each_from(head, rht_ptr(bkt, tbl, hash), tbl, hash) {
742 		struct rhlist_head *plist;
743 		struct rhlist_head *list;
744 
745 		elasticity--;
746 		if (!key ||
747 		    (params.obj_cmpfn ?
748 		     params.obj_cmpfn(&arg, rht_obj(ht, head)) :
749 		     rhashtable_compare(&arg, rht_obj(ht, head)))) {
750 			pprev = &head->next;
751 			continue;
752 		}
753 
754 		data = rht_obj(ht, head);
755 
756 		if (!rhlist)
757 			goto out_unlock;
758 
759 
760 		list = container_of(obj, struct rhlist_head, rhead);
761 		plist = container_of(head, struct rhlist_head, rhead);
762 
763 		RCU_INIT_POINTER(list->next, plist);
764 		head = rht_dereference_bucket(head->next, tbl, hash);
765 		RCU_INIT_POINTER(list->rhead.next, head);
766 		if (pprev) {
767 			rcu_assign_pointer(*pprev, obj);
768 			rht_unlock(tbl, bkt, flags);
769 		} else
770 			rht_assign_unlock(tbl, bkt, obj, flags);
771 		data = NULL;
772 		goto out;
773 	}
774 
775 	if (elasticity <= 0)
776 		goto slow_path;
777 
778 	data = ERR_PTR(-E2BIG);
779 	if (unlikely(rht_grow_above_max(ht, tbl)))
780 		goto out_unlock;
781 
782 	if (unlikely(rht_grow_above_100(ht, tbl)))
783 		goto slow_path;
784 
785 	/* Inserting at head of list makes unlocking free. */
786 	head = rht_ptr(bkt, tbl, hash);
787 
788 	RCU_INIT_POINTER(obj->next, head);
789 	if (rhlist) {
790 		struct rhlist_head *list;
791 
792 		list = container_of(obj, struct rhlist_head, rhead);
793 		RCU_INIT_POINTER(list->next, NULL);
794 	}
795 
796 	atomic_inc(&ht->nelems);
797 	rht_assign_unlock(tbl, bkt, obj, flags);
798 
799 	if (rht_grow_above_75(ht, tbl))
800 		schedule_work(&ht->run_work);
801 
802 	data = NULL;
803 out:
804 	rcu_read_unlock();
805 
806 	return data;
807 
808 out_unlock:
809 	rht_unlock(tbl, bkt, flags);
810 	goto out;
811 }
812 
813 /**
814  * rhashtable_insert_fast - insert object into hash table
815  * @ht:		hash table
816  * @obj:	pointer to hash head inside object
817  * @params:	hash table parameters
818  *
819  * Will take the per bucket bitlock to protect against mutual mutations
820  * on the same bucket. Multiple insertions may occur in parallel unless
821  * they map to the same bucket.
822  *
823  * It is safe to call this function from atomic context.
824  *
825  * Will trigger an automatic deferred table resizing if residency in the
826  * table grows beyond 70%.
827  */
rhashtable_insert_fast(struct rhashtable * ht,struct rhash_head * obj,const struct rhashtable_params params)828 static inline int rhashtable_insert_fast(
829 	struct rhashtable *ht, struct rhash_head *obj,
830 	const struct rhashtable_params params)
831 {
832 	void *ret;
833 
834 	ret = __rhashtable_insert_fast(ht, NULL, obj, params, false);
835 	if (IS_ERR(ret))
836 		return PTR_ERR(ret);
837 
838 	return ret == NULL ? 0 : -EEXIST;
839 }
840 
841 /**
842  * rhltable_insert_key - insert object into hash list table
843  * @hlt:	hash list table
844  * @key:	the pointer to the key
845  * @list:	pointer to hash list head inside object
846  * @params:	hash table parameters
847  *
848  * Will take the per bucket bitlock to protect against mutual mutations
849  * on the same bucket. Multiple insertions may occur in parallel unless
850  * they map to the same bucket.
851  *
852  * It is safe to call this function from atomic context.
853  *
854  * Will trigger an automatic deferred table resizing if residency in the
855  * table grows beyond 70%.
856  */
rhltable_insert_key(struct rhltable * hlt,const void * key,struct rhlist_head * list,const struct rhashtable_params params)857 static inline int rhltable_insert_key(
858 	struct rhltable *hlt, const void *key, struct rhlist_head *list,
859 	const struct rhashtable_params params)
860 {
861 	return PTR_ERR(__rhashtable_insert_fast(&hlt->ht, key, &list->rhead,
862 						params, true));
863 }
864 
865 /**
866  * rhltable_insert - insert object into hash list table
867  * @hlt:	hash list table
868  * @list:	pointer to hash list head inside object
869  * @params:	hash table parameters
870  *
871  * Will take the per bucket bitlock to protect against mutual mutations
872  * on the same bucket. Multiple insertions may occur in parallel unless
873  * they map to the same bucket.
874  *
875  * It is safe to call this function from atomic context.
876  *
877  * Will trigger an automatic deferred table resizing if residency in the
878  * table grows beyond 70%.
879  */
rhltable_insert(struct rhltable * hlt,struct rhlist_head * list,const struct rhashtable_params params)880 static inline int rhltable_insert(
881 	struct rhltable *hlt, struct rhlist_head *list,
882 	const struct rhashtable_params params)
883 {
884 	const char *key = rht_obj(&hlt->ht, &list->rhead);
885 
886 	key += params.key_offset;
887 
888 	return rhltable_insert_key(hlt, key, list, params);
889 }
890 
891 /**
892  * rhashtable_lookup_insert_fast - lookup and insert object into hash table
893  * @ht:		hash table
894  * @obj:	pointer to hash head inside object
895  * @params:	hash table parameters
896  *
897  * This lookup function may only be used for fixed key hash table (key_len
898  * parameter set). It will BUG() if used inappropriately.
899  *
900  * It is safe to call this function from atomic context.
901  *
902  * Will trigger an automatic deferred table resizing if residency in the
903  * table grows beyond 70%.
904  */
rhashtable_lookup_insert_fast(struct rhashtable * ht,struct rhash_head * obj,const struct rhashtable_params params)905 static inline int rhashtable_lookup_insert_fast(
906 	struct rhashtable *ht, struct rhash_head *obj,
907 	const struct rhashtable_params params)
908 {
909 	const char *key = rht_obj(ht, obj);
910 	void *ret;
911 
912 	BUG_ON(ht->p.obj_hashfn);
913 
914 	ret = __rhashtable_insert_fast(ht, key + ht->p.key_offset, obj, params,
915 				       false);
916 	if (IS_ERR(ret))
917 		return PTR_ERR(ret);
918 
919 	return ret == NULL ? 0 : -EEXIST;
920 }
921 
922 /**
923  * rhashtable_lookup_get_insert_fast - lookup and insert object into hash table
924  * @ht:		hash table
925  * @obj:	pointer to hash head inside object
926  * @params:	hash table parameters
927  *
928  * Just like rhashtable_lookup_insert_fast(), but this function returns the
929  * object if it exists, NULL if it did not and the insertion was successful,
930  * and an ERR_PTR otherwise.
931  */
rhashtable_lookup_get_insert_fast(struct rhashtable * ht,struct rhash_head * obj,const struct rhashtable_params params)932 static inline void *rhashtable_lookup_get_insert_fast(
933 	struct rhashtable *ht, struct rhash_head *obj,
934 	const struct rhashtable_params params)
935 {
936 	const char *key = rht_obj(ht, obj);
937 
938 	BUG_ON(ht->p.obj_hashfn);
939 
940 	return __rhashtable_insert_fast(ht, key + ht->p.key_offset, obj, params,
941 					false);
942 }
943 
944 /**
945  * rhashtable_lookup_insert_key - search and insert object to hash table
946  *				  with explicit key
947  * @ht:		hash table
948  * @key:	key
949  * @obj:	pointer to hash head inside object
950  * @params:	hash table parameters
951  *
952  * Lookups may occur in parallel with hashtable mutations and resizing.
953  *
954  * Will trigger an automatic deferred table resizing if residency in the
955  * table grows beyond 70%.
956  *
957  * Returns zero on success.
958  */
rhashtable_lookup_insert_key(struct rhashtable * ht,const void * key,struct rhash_head * obj,const struct rhashtable_params params)959 static inline int rhashtable_lookup_insert_key(
960 	struct rhashtable *ht, const void *key, struct rhash_head *obj,
961 	const struct rhashtable_params params)
962 {
963 	void *ret;
964 
965 	BUG_ON(!ht->p.obj_hashfn || !key);
966 
967 	ret = __rhashtable_insert_fast(ht, key, obj, params, false);
968 	if (IS_ERR(ret))
969 		return PTR_ERR(ret);
970 
971 	return ret == NULL ? 0 : -EEXIST;
972 }
973 
974 /**
975  * rhashtable_lookup_get_insert_key - lookup and insert object into hash table
976  * @ht:		hash table
977  * @key:	key
978  * @obj:	pointer to hash head inside object
979  * @params:	hash table parameters
980  *
981  * Just like rhashtable_lookup_insert_key(), but this function returns the
982  * object if it exists, NULL if it does not and the insertion was successful,
983  * and an ERR_PTR otherwise.
984  */
rhashtable_lookup_get_insert_key(struct rhashtable * ht,const void * key,struct rhash_head * obj,const struct rhashtable_params params)985 static inline void *rhashtable_lookup_get_insert_key(
986 	struct rhashtable *ht, const void *key, struct rhash_head *obj,
987 	const struct rhashtable_params params)
988 {
989 	BUG_ON(!ht->p.obj_hashfn || !key);
990 
991 	return __rhashtable_insert_fast(ht, key, obj, params, false);
992 }
993 
994 /* Internal function, please use rhashtable_remove_fast() instead */
__rhashtable_remove_fast_one(struct rhashtable * ht,struct bucket_table * tbl,struct rhash_head * obj,const struct rhashtable_params params,bool rhlist)995 static inline int __rhashtable_remove_fast_one(
996 	struct rhashtable *ht, struct bucket_table *tbl,
997 	struct rhash_head *obj, const struct rhashtable_params params,
998 	bool rhlist)
999 {
1000 	struct rhash_lock_head __rcu **bkt;
1001 	struct rhash_head __rcu **pprev;
1002 	struct rhash_head *he;
1003 	unsigned long flags;
1004 	unsigned int hash;
1005 	int err = -ENOENT;
1006 
1007 	hash = rht_head_hashfn(ht, tbl, obj, params);
1008 	bkt = rht_bucket_var(tbl, hash);
1009 	if (!bkt)
1010 		return -ENOENT;
1011 	pprev = NULL;
1012 	flags = rht_lock(tbl, bkt);
1013 
1014 	rht_for_each_from(he, rht_ptr(bkt, tbl, hash), tbl, hash) {
1015 		struct rhlist_head *list;
1016 
1017 		list = container_of(he, struct rhlist_head, rhead);
1018 
1019 		if (he != obj) {
1020 			struct rhlist_head __rcu **lpprev;
1021 
1022 			pprev = &he->next;
1023 
1024 			if (!rhlist)
1025 				continue;
1026 
1027 			do {
1028 				lpprev = &list->next;
1029 				list = rht_dereference_bucket(list->next,
1030 							      tbl, hash);
1031 			} while (list && obj != &list->rhead);
1032 
1033 			if (!list)
1034 				continue;
1035 
1036 			list = rht_dereference_bucket(list->next, tbl, hash);
1037 			RCU_INIT_POINTER(*lpprev, list);
1038 			err = 0;
1039 			break;
1040 		}
1041 
1042 		obj = rht_dereference_bucket(obj->next, tbl, hash);
1043 		err = 1;
1044 
1045 		if (rhlist) {
1046 			list = rht_dereference_bucket(list->next, tbl, hash);
1047 			if (list) {
1048 				RCU_INIT_POINTER(list->rhead.next, obj);
1049 				obj = &list->rhead;
1050 				err = 0;
1051 			}
1052 		}
1053 
1054 		if (pprev) {
1055 			rcu_assign_pointer(*pprev, obj);
1056 			rht_unlock(tbl, bkt, flags);
1057 		} else {
1058 			rht_assign_unlock(tbl, bkt, obj, flags);
1059 		}
1060 		goto unlocked;
1061 	}
1062 
1063 	rht_unlock(tbl, bkt, flags);
1064 unlocked:
1065 	if (err > 0) {
1066 		atomic_dec(&ht->nelems);
1067 		if (unlikely(ht->p.automatic_shrinking &&
1068 			     rht_shrink_below_30(ht, tbl)))
1069 			schedule_work(&ht->run_work);
1070 		err = 0;
1071 	}
1072 
1073 	return err;
1074 }
1075 
1076 /* Internal function, please use rhashtable_remove_fast() instead */
__rhashtable_remove_fast(struct rhashtable * ht,struct rhash_head * obj,const struct rhashtable_params params,bool rhlist)1077 static inline int __rhashtable_remove_fast(
1078 	struct rhashtable *ht, struct rhash_head *obj,
1079 	const struct rhashtable_params params, bool rhlist)
1080 {
1081 	struct bucket_table *tbl;
1082 	int err;
1083 
1084 	rcu_read_lock();
1085 
1086 	tbl = rht_dereference_rcu(ht->tbl, ht);
1087 
1088 	/* Because we have already taken (and released) the bucket
1089 	 * lock in old_tbl, if we find that future_tbl is not yet
1090 	 * visible then that guarantees the entry to still be in
1091 	 * the old tbl if it exists.
1092 	 */
1093 	while ((err = __rhashtable_remove_fast_one(ht, tbl, obj, params,
1094 						   rhlist)) &&
1095 	       (tbl = rht_dereference_rcu(tbl->future_tbl, ht)))
1096 		;
1097 
1098 	rcu_read_unlock();
1099 
1100 	return err;
1101 }
1102 
1103 /**
1104  * rhashtable_remove_fast - remove object from hash table
1105  * @ht:		hash table
1106  * @obj:	pointer to hash head inside object
1107  * @params:	hash table parameters
1108  *
1109  * Since the hash chain is single linked, the removal operation needs to
1110  * walk the bucket chain upon removal. The removal operation is thus
1111  * considerable slow if the hash table is not correctly sized.
1112  *
1113  * Will automatically shrink the table if permitted when residency drops
1114  * below 30%.
1115  *
1116  * Returns zero on success, -ENOENT if the entry could not be found.
1117  */
rhashtable_remove_fast(struct rhashtable * ht,struct rhash_head * obj,const struct rhashtable_params params)1118 static inline int rhashtable_remove_fast(
1119 	struct rhashtable *ht, struct rhash_head *obj,
1120 	const struct rhashtable_params params)
1121 {
1122 	return __rhashtable_remove_fast(ht, obj, params, false);
1123 }
1124 
1125 /**
1126  * rhltable_remove - remove object from hash list table
1127  * @hlt:	hash list table
1128  * @list:	pointer to hash list head inside object
1129  * @params:	hash table parameters
1130  *
1131  * Since the hash chain is single linked, the removal operation needs to
1132  * walk the bucket chain upon removal. The removal operation is thus
1133  * considerable slow if the hash table is not correctly sized.
1134  *
1135  * Will automatically shrink the table if permitted when residency drops
1136  * below 30%
1137  *
1138  * Returns zero on success, -ENOENT if the entry could not be found.
1139  */
rhltable_remove(struct rhltable * hlt,struct rhlist_head * list,const struct rhashtable_params params)1140 static inline int rhltable_remove(
1141 	struct rhltable *hlt, struct rhlist_head *list,
1142 	const struct rhashtable_params params)
1143 {
1144 	return __rhashtable_remove_fast(&hlt->ht, &list->rhead, params, true);
1145 }
1146 
1147 /* Internal function, please use rhashtable_replace_fast() instead */
__rhashtable_replace_fast(struct rhashtable * ht,struct bucket_table * tbl,struct rhash_head * obj_old,struct rhash_head * obj_new,const struct rhashtable_params params)1148 static inline int __rhashtable_replace_fast(
1149 	struct rhashtable *ht, struct bucket_table *tbl,
1150 	struct rhash_head *obj_old, struct rhash_head *obj_new,
1151 	const struct rhashtable_params params)
1152 {
1153 	struct rhash_lock_head __rcu **bkt;
1154 	struct rhash_head __rcu **pprev;
1155 	struct rhash_head *he;
1156 	unsigned long flags;
1157 	unsigned int hash;
1158 	int err = -ENOENT;
1159 
1160 	/* Minimally, the old and new objects must have same hash
1161 	 * (which should mean identifiers are the same).
1162 	 */
1163 	hash = rht_head_hashfn(ht, tbl, obj_old, params);
1164 	if (hash != rht_head_hashfn(ht, tbl, obj_new, params))
1165 		return -EINVAL;
1166 
1167 	bkt = rht_bucket_var(tbl, hash);
1168 	if (!bkt)
1169 		return -ENOENT;
1170 
1171 	pprev = NULL;
1172 	flags = rht_lock(tbl, bkt);
1173 
1174 	rht_for_each_from(he, rht_ptr(bkt, tbl, hash), tbl, hash) {
1175 		if (he != obj_old) {
1176 			pprev = &he->next;
1177 			continue;
1178 		}
1179 
1180 		rcu_assign_pointer(obj_new->next, obj_old->next);
1181 		if (pprev) {
1182 			rcu_assign_pointer(*pprev, obj_new);
1183 			rht_unlock(tbl, bkt, flags);
1184 		} else {
1185 			rht_assign_unlock(tbl, bkt, obj_new, flags);
1186 		}
1187 		err = 0;
1188 		goto unlocked;
1189 	}
1190 
1191 	rht_unlock(tbl, bkt, flags);
1192 
1193 unlocked:
1194 	return err;
1195 }
1196 
1197 /**
1198  * rhashtable_replace_fast - replace an object in hash table
1199  * @ht:		hash table
1200  * @obj_old:	pointer to hash head inside object being replaced
1201  * @obj_new:	pointer to hash head inside object which is new
1202  * @params:	hash table parameters
1203  *
1204  * Replacing an object doesn't affect the number of elements in the hash table
1205  * or bucket, so we don't need to worry about shrinking or expanding the
1206  * table here.
1207  *
1208  * Returns zero on success, -ENOENT if the entry could not be found,
1209  * -EINVAL if hash is not the same for the old and new objects.
1210  */
rhashtable_replace_fast(struct rhashtable * ht,struct rhash_head * obj_old,struct rhash_head * obj_new,const struct rhashtable_params params)1211 static inline int rhashtable_replace_fast(
1212 	struct rhashtable *ht, struct rhash_head *obj_old,
1213 	struct rhash_head *obj_new,
1214 	const struct rhashtable_params params)
1215 {
1216 	struct bucket_table *tbl;
1217 	int err;
1218 
1219 	rcu_read_lock();
1220 
1221 	tbl = rht_dereference_rcu(ht->tbl, ht);
1222 
1223 	/* Because we have already taken (and released) the bucket
1224 	 * lock in old_tbl, if we find that future_tbl is not yet
1225 	 * visible then that guarantees the entry to still be in
1226 	 * the old tbl if it exists.
1227 	 */
1228 	while ((err = __rhashtable_replace_fast(ht, tbl, obj_old,
1229 						obj_new, params)) &&
1230 	       (tbl = rht_dereference_rcu(tbl->future_tbl, ht)))
1231 		;
1232 
1233 	rcu_read_unlock();
1234 
1235 	return err;
1236 }
1237 
1238 /**
1239  * rhltable_walk_enter - Initialise an iterator
1240  * @hlt:	Table to walk over
1241  * @iter:	Hash table Iterator
1242  *
1243  * This function prepares a hash table walk.
1244  *
1245  * Note that if you restart a walk after rhashtable_walk_stop you
1246  * may see the same object twice.  Also, you may miss objects if
1247  * there are removals in between rhashtable_walk_stop and the next
1248  * call to rhashtable_walk_start.
1249  *
1250  * For a completely stable walk you should construct your own data
1251  * structure outside the hash table.
1252  *
1253  * This function may be called from any process context, including
1254  * non-preemptable context, but cannot be called from softirq or
1255  * hardirq context.
1256  *
1257  * You must call rhashtable_walk_exit after this function returns.
1258  */
rhltable_walk_enter(struct rhltable * hlt,struct rhashtable_iter * iter)1259 static inline void rhltable_walk_enter(struct rhltable *hlt,
1260 				       struct rhashtable_iter *iter)
1261 {
1262 	return rhashtable_walk_enter(&hlt->ht, iter);
1263 }
1264 
1265 /**
1266  * rhltable_free_and_destroy - free elements and destroy hash list table
1267  * @hlt:	the hash list table to destroy
1268  * @free_fn:	callback to release resources of element
1269  * @arg:	pointer passed to free_fn
1270  *
1271  * See documentation for rhashtable_free_and_destroy.
1272  */
rhltable_free_and_destroy(struct rhltable * hlt,void (* free_fn)(void * ptr,void * arg),void * arg)1273 static inline void rhltable_free_and_destroy(struct rhltable *hlt,
1274 					     void (*free_fn)(void *ptr,
1275 							     void *arg),
1276 					     void *arg)
1277 {
1278 	return rhashtable_free_and_destroy(&hlt->ht, free_fn, arg);
1279 }
1280 
rhltable_destroy(struct rhltable * hlt)1281 static inline void rhltable_destroy(struct rhltable *hlt)
1282 {
1283 	return rhltable_free_and_destroy(hlt, NULL, NULL);
1284 }
1285 
1286 #endif /* _LINUX_RHASHTABLE_H */
1287