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2023-12-08 01573e231f18eb2d99162747186f59511f56b64d 
 kernel/lib/rhashtable.c
....@@ -1,3 +1,4 @@
1
+// SPDX-License-Identifier: GPL-2.0-only
12 /*
23  * Resizable, Scalable, Concurrent Hash Table
34  *
....@@ -8,10 +9,6 @@
89  * Code partially derived from nft_hash
910  * Rewritten with rehash code from br_multicast plus single list
1011  * 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.
1512  */
1613 
1714 #include <linux/atomic.h>
....@@ -31,11 +28,10 @@
3128 
3229 #define HASH_DEFAULT_SIZE	64UL
3330 #define HASH_MIN_SIZE		4U
34
-#define BUCKET_LOCKS_PER_CPU	32UL
3531 
3632 union nested_table {
3733 	union nested_table __rcu *table;
38
-	struct rhash_head __rcu *bucket;
34
+	struct rhash_lock_head __rcu *bucket;
3935 };
4036 
4137 static u32 head_hashfn(struct rhashtable *ht,
....@@ -56,14 +52,25 @@
5652 
5753 int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash)
5854 {
59
-	spinlock_t *lock = rht_bucket_lock(tbl, hash);
60
-
61
-	return (debug_locks) ? lockdep_is_held(lock) : 1;
55
+	if (!debug_locks)
56
+		return 1;
57
+	if (unlikely(tbl->nest))
58
+		return 1;
59
+	return bit_spin_is_locked(0, (unsigned long *)&tbl->buckets[hash]);
6260 }
6361 EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held);
6462 #else
6563 #define ASSERT_RHT_MUTEX(HT)
6664 #endif
65
+
66
+static inline union nested_table *nested_table_top(
67
+	const struct bucket_table *tbl)
68
+{
69
+	/* The top-level bucket entry does not need RCU protection
70
+	 * because it's set at the same time as tbl->nest.
71
+	 */
72
+	return (void *)rcu_dereference_protected(tbl->buckets[0], 1);
73
+}
6774 
6875 static void nested_table_free(union nested_table *ntbl, unsigned int size)
6976 {
....@@ -71,7 +78,7 @@
7178 	const unsigned int len = 1 << shift;
7279 	unsigned int i;
7380 
74
-	ntbl = rcu_dereference_raw(ntbl->table);
81
+	ntbl = rcu_dereference_protected(ntbl->table, 1);
7582 	if (!ntbl)
7683 		return;
7784 
....@@ -91,7 +98,7 @@
9198 	union nested_table *ntbl;
9299 	unsigned int i;
93100 
94
-	ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
101
+	ntbl = nested_table_top(tbl);
95102 
96103 	for (i = 0; i < len; i++)
97104 		nested_table_free(ntbl + i, size);
....@@ -104,7 +111,6 @@
104111 	if (tbl->nest)
105112 		nested_bucket_table_free(tbl);
106113 
107
-	free_bucket_spinlocks(tbl->locks);
108114 	kvfree(tbl);
109115 }
110116 
....@@ -131,9 +137,11 @@
131137 			INIT_RHT_NULLS_HEAD(ntbl[i].bucket);
132138 	}
133139 
134
-	rcu_assign_pointer(*prev, ntbl);
135
-
136
-	return ntbl;
140
+	if (cmpxchg((union nested_table **)prev, NULL, ntbl) == NULL)
141
+		return ntbl;
142
+	/* Raced with another thread. */
143
+	kfree(ntbl);
144
+	return rcu_dereference(*prev);
137145 }
138146 
139147 static struct bucket_table *nested_bucket_table_alloc(struct rhashtable *ht,
....@@ -169,11 +177,11 @@
169177 					       gfp_t gfp)
170178 {
171179 	struct bucket_table *tbl = NULL;
172
-	size_t size, max_locks;
180
+	size_t size;
173181 	int i;
182
+	static struct lock_class_key __key;
174183 
175
-	size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]);
176
-	tbl = kvzalloc(size, gfp);
184
+	tbl = kvzalloc(struct_size(tbl, buckets, nbuckets), gfp);
177185 
178186 	size = nbuckets;
179187 
....@@ -185,18 +193,11 @@
185193 	if (tbl == NULL)
186194 		return NULL;
187195 
196
+	lockdep_init_map(&tbl->dep_map, "rhashtable_bucket", &__key, 0);
197
+
188198 	tbl->size = size;
189199 
190
-	max_locks = size >> 1;
191
-	if (tbl->nest)
192
-		max_locks = min_t(size_t, max_locks, 1U << tbl->nest);
193
-
194
-	if (alloc_bucket_spinlocks(&tbl->locks, &tbl->locks_mask, max_locks,
195
-				   ht->p.locks_mul, gfp) < 0) {
196
-		bucket_table_free(tbl);
197
-		return NULL;
198
-	}
199
-
200
+	rcu_head_init(&tbl->rcu);
200201 	INIT_LIST_HEAD(&tbl->walkers);
201202 
202203 	tbl->hash_rnd = get_random_u32();
....@@ -220,14 +221,15 @@
220221 	return new_tbl;
221222 }
222223 
223
-static int rhashtable_rehash_one(struct rhashtable *ht, unsigned int old_hash)
224
+static int rhashtable_rehash_one(struct rhashtable *ht,
225
+				 struct rhash_lock_head __rcu **bkt,
226
+				 unsigned int old_hash)
224227 {
225228 	struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
226229 	struct bucket_table *new_tbl = rhashtable_last_table(ht, old_tbl);
227
-	struct rhash_head __rcu **pprev = rht_bucket_var(old_tbl, old_hash);
228230 	int err = -EAGAIN;
229231 	struct rhash_head *head, *next, *entry;
230
-	spinlock_t *new_bucket_lock;
232
+	struct rhash_head __rcu **pprev = NULL;
231233 	unsigned int new_hash;
232234 
233235 	if (new_tbl->nest)
....@@ -235,7 +237,8 @@
235237 
236238 	err = -ENOENT;
237239 
238
-	rht_for_each(entry, old_tbl, old_hash) {
240
+	rht_for_each_from(entry, rht_ptr(bkt, old_tbl, old_hash),
241
+			  old_tbl, old_hash) {
239242 		err = 0;
240243 		next = rht_dereference_bucket(entry->next, old_tbl, old_hash);
241244 
....@@ -250,18 +253,19 @@
250253 
251254 	new_hash = head_hashfn(ht, new_tbl, entry);
252255 
253
-	new_bucket_lock = rht_bucket_lock(new_tbl, new_hash);
256
+	rht_lock_nested(new_tbl, &new_tbl->buckets[new_hash], SINGLE_DEPTH_NESTING);
254257 
255
-	spin_lock_nested(new_bucket_lock, SINGLE_DEPTH_NESTING);
256
-	head = rht_dereference_bucket(new_tbl->buckets[new_hash],
257
-				      new_tbl, new_hash);
258
+	head = rht_ptr(new_tbl->buckets + new_hash, new_tbl, new_hash);
258259 
259260 	RCU_INIT_POINTER(entry->next, head);
260261 
261
-	rcu_assign_pointer(new_tbl->buckets[new_hash], entry);
262
-	spin_unlock(new_bucket_lock);
262
+	rht_assign_unlock(new_tbl, &new_tbl->buckets[new_hash], entry);
263263 
264
-	rcu_assign_pointer(*pprev, next);
264
+	if (pprev)
265
+		rcu_assign_pointer(*pprev, next);
266
+	else
267
+		/* Need to preserved the bit lock. */
268
+		rht_assign_locked(bkt, next);
265269 
266270 out:
267271 	return err;
....@@ -271,20 +275,19 @@
271275 				    unsigned int old_hash)
272276 {
273277 	struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
274
-	spinlock_t *old_bucket_lock;
278
+	struct rhash_lock_head __rcu **bkt = rht_bucket_var(old_tbl, old_hash);
275279 	int err;
276280 
277
-	old_bucket_lock = rht_bucket_lock(old_tbl, old_hash);
281
+	if (!bkt)
282
+		return 0;
283
+	rht_lock(old_tbl, bkt);
278284 
279
-	spin_lock_bh(old_bucket_lock);
280
-	while (!(err = rhashtable_rehash_one(ht, old_hash)))
285
+	while (!(err = rhashtable_rehash_one(ht, bkt, old_hash)))
281286 		;
282287 
283
-	if (err == -ENOENT) {
284
-		old_tbl->rehash++;
288
+	if (err == -ENOENT)
285289 		err = 0;
286
-	}
287
-	spin_unlock_bh(old_bucket_lock);
290
+	rht_unlock(old_tbl, bkt);
288291 
289292 	return err;
290293 }
....@@ -299,7 +302,8 @@
299302 	 * rcu_assign_pointer().
300303 	 */
301304 
302
-	if (cmpxchg(&old_tbl->future_tbl, NULL, new_tbl) != NULL)
305
+	if (cmpxchg((struct bucket_table **)&old_tbl->future_tbl, NULL,
306
+		    new_tbl) != NULL)
303307 		return -EEXIST;
304308 
305309 	return 0;
....@@ -330,13 +334,16 @@
330334 	spin_lock(&ht->lock);
331335 	list_for_each_entry(walker, &old_tbl->walkers, list)
332336 		walker->tbl = NULL;
333
-	spin_unlock(&ht->lock);
334337 
335338 	/* Wait for readers. All new readers will see the new
336339 	 * table, and thus no references to the old table will
337340 	 * remain.
341
+	 * We do this inside the locked region so that
342
+	 * rhashtable_walk_stop() can use rcu_head_after_call_rcu()
343
+	 * to check if it should not re-link the table.
338344 	 */
339345 	call_rcu(&old_tbl->rcu, bucket_table_free_rcu);
346
+	spin_unlock(&ht->lock);
340347 
341348 	return rht_dereference(new_tbl->future_tbl, ht) ? -EAGAIN : 0;
342349 }
....@@ -478,6 +485,7 @@
478485 }
479486 
480487 static void *rhashtable_lookup_one(struct rhashtable *ht,
488
+				   struct rhash_lock_head __rcu **bkt,
481489 				   struct bucket_table *tbl, unsigned int hash,
482490 				   const void *key, struct rhash_head *obj)
483491 {
....@@ -485,13 +493,12 @@
485493 		.ht = ht,
486494 		.key = key,
487495 	};
488
-	struct rhash_head __rcu **pprev;
496
+	struct rhash_head __rcu **pprev = NULL;
489497 	struct rhash_head *head;
490498 	int elasticity;
491499 
492500 	elasticity = RHT_ELASTICITY;
493
-	pprev = rht_bucket_var(tbl, hash);
494
-	rht_for_each_continue(head, *pprev, tbl, hash) {
501
+	rht_for_each_from(head, rht_ptr(bkt, tbl, hash), tbl, hash) {
495502 		struct rhlist_head *list;
496503 		struct rhlist_head *plist;
497504 
....@@ -513,7 +520,11 @@
513520 		RCU_INIT_POINTER(list->next, plist);
514521 		head = rht_dereference_bucket(head->next, tbl, hash);
515522 		RCU_INIT_POINTER(list->rhead.next, head);
516
-		rcu_assign_pointer(*pprev, obj);
523
+		if (pprev)
524
+			rcu_assign_pointer(*pprev, obj);
525
+		else
526
+			/* Need to preserve the bit lock */
527
+			rht_assign_locked(bkt, obj);
517528 
518529 		return NULL;
519530 	}
....@@ -524,13 +535,11 @@
524535 	return ERR_PTR(-ENOENT);
525536 }
526537 
527
-static struct bucket_table *rhashtable_insert_one(struct rhashtable *ht,
528
-						  struct bucket_table *tbl,
529
-						  unsigned int hash,
530
-						  struct rhash_head *obj,
531
-						  void *data)
538
+static struct bucket_table *rhashtable_insert_one(
539
+	struct rhashtable *ht, struct rhash_lock_head __rcu **bkt,
540
+	struct bucket_table *tbl, unsigned int hash, struct rhash_head *obj,
541
+	void *data)
532542 {
533
-	struct rhash_head __rcu **pprev;
534543 	struct bucket_table *new_tbl;
535544 	struct rhash_head *head;
536545 
....@@ -553,11 +562,7 @@
553562 	if (unlikely(rht_grow_above_100(ht, tbl)))
554563 		return ERR_PTR(-EAGAIN);
555564 
556
-	pprev = rht_bucket_insert(ht, tbl, hash);
557
-	if (!pprev)
558
-		return ERR_PTR(-ENOMEM);
559
-
560
-	head = rht_dereference_bucket(*pprev, tbl, hash);
565
+	head = rht_ptr(bkt, tbl, hash);
561566 
562567 	RCU_INIT_POINTER(obj->next, head);
563568 	if (ht->rhlist) {
....@@ -567,7 +572,10 @@
567572 		RCU_INIT_POINTER(list->next, NULL);
568573 	}
569574 
570
-	rcu_assign_pointer(*pprev, obj);
575
+	/* bkt is always the head of the list, so it holds
576
+	 * the lock, which we need to preserve
577
+	 */
578
+	rht_assign_locked(bkt, obj);
571579 
572580 	atomic_inc(&ht->nelems);
573581 	if (rht_grow_above_75(ht, tbl))
....@@ -581,47 +589,35 @@
581589 {
582590 	struct bucket_table *new_tbl;
583591 	struct bucket_table *tbl;
592
+	struct rhash_lock_head __rcu **bkt;
584593 	unsigned int hash;
585
-	spinlock_t *lock;
586594 	void *data;
587595 
588
-	tbl = rcu_dereference(ht->tbl);
596
+	new_tbl = rcu_dereference(ht->tbl);
589597 
590
-	/* All insertions must grab the oldest table containing
591
-	 * the hashed bucket that is yet to be rehashed.
592
-	 */
593
-	for (;;) {
594
-		hash = rht_head_hashfn(ht, tbl, obj, ht->p);
595
-		lock = rht_bucket_lock(tbl, hash);
596
-		spin_lock_bh(lock);
597
-
598
-		if (tbl->rehash <= hash)
599
-			break;
600
-
601
-		spin_unlock_bh(lock);
602
-		tbl = rht_dereference_rcu(tbl->future_tbl, ht);
603
-	}
604
-
605
-	data = rhashtable_lookup_one(ht, tbl, hash, key, obj);
606
-	new_tbl = rhashtable_insert_one(ht, tbl, hash, obj, data);
607
-	if (PTR_ERR(new_tbl) != -EEXIST)
608
-		data = ERR_CAST(new_tbl);
609
-
610
-	while (!IS_ERR_OR_NULL(new_tbl)) {
598
+	do {
611599 		tbl = new_tbl;
612600 		hash = rht_head_hashfn(ht, tbl, obj, ht->p);
613
-		spin_lock_nested(rht_bucket_lock(tbl, hash),
614
-				 SINGLE_DEPTH_NESTING);
601
+		if (rcu_access_pointer(tbl->future_tbl))
602
+			/* Failure is OK */
603
+			bkt = rht_bucket_var(tbl, hash);
604
+		else
605
+			bkt = rht_bucket_insert(ht, tbl, hash);
606
+		if (bkt == NULL) {
607
+			new_tbl = rht_dereference_rcu(tbl->future_tbl, ht);
608
+			data = ERR_PTR(-EAGAIN);
609
+		} else {
610
+			rht_lock(tbl, bkt);
611
+			data = rhashtable_lookup_one(ht, bkt, tbl,
612
+						     hash, key, obj);
613
+			new_tbl = rhashtable_insert_one(ht, bkt, tbl,
614
+							hash, obj, data);
615
+			if (PTR_ERR(new_tbl) != -EEXIST)
616
+				data = ERR_CAST(new_tbl);
615617 
616
-		data = rhashtable_lookup_one(ht, tbl, hash, key, obj);
617
-		new_tbl = rhashtable_insert_one(ht, tbl, hash, obj, data);
618
-		if (PTR_ERR(new_tbl) != -EEXIST)
619
-			data = ERR_CAST(new_tbl);
620
-
621
-		spin_unlock(rht_bucket_lock(tbl, hash));
622
-	}
623
-
624
-	spin_unlock_bh(lock);
618
+			rht_unlock(tbl, bkt);
619
+		}
620
+	} while (!IS_ERR_OR_NULL(new_tbl));
625621 
626622 	if (PTR_ERR(data) == -EAGAIN)
627623 		data = ERR_PTR(rhashtable_insert_rehash(ht, tbl) ?:
....@@ -686,7 +682,7 @@
686682  * rhashtable_walk_exit - Free an iterator
687683  * @iter:	Hash table Iterator
688684  *
689
- * This function frees resources allocated by rhashtable_walk_init.
685
+ * This function frees resources allocated by rhashtable_walk_enter.
690686  */
691687 void rhashtable_walk_exit(struct rhashtable_iter *iter)
692688 {
....@@ -943,10 +939,11 @@
943939 	ht = iter->ht;
944940 
945941 	spin_lock(&ht->lock);
946
-	if (tbl->rehash < tbl->size)
947
-		list_add(&iter->walker.list, &tbl->walkers);
948
-	else
942
+	if (rcu_head_after_call_rcu(&tbl->rcu, bucket_table_free_rcu))
943
+		/* This bucket table is being freed, don't re-link it. */
949944 		iter->walker.tbl = NULL;
945
+	else
946
+		list_add(&iter->walker.list, &tbl->walkers);
950947 	spin_unlock(&ht->lock);
951948 
952949 out:
....@@ -1045,11 +1042,6 @@
10451042 	ht->p.min_size = max_t(u16, ht->p.min_size, HASH_MIN_SIZE);
10461043 
10471044 	size = rounded_hashtable_size(&ht->p);
1048
-
1049
-	if (params->locks_mul)
1050
-		ht->p.locks_mul = roundup_pow_of_two(params->locks_mul);
1051
-	else
1052
-		ht->p.locks_mul = BUCKET_LOCKS_PER_CPU;
10531045 
10541046 	ht->key_len = ht->p.key_len;
10551047 	if (!params->hashfn) {
....@@ -1152,7 +1144,7 @@
11521144 			struct rhash_head *pos, *next;
11531145 
11541146 			cond_resched();
1155
-			for (pos = rht_dereference(*rht_bucket(tbl, i), ht),
1147
+			for (pos = rht_ptr_exclusive(rht_bucket(tbl, i)),
11561148 			     next = !rht_is_a_nulls(pos) ?
11571149 					rht_dereference(pos->next, ht) : NULL;
11581150 			     !rht_is_a_nulls(pos);
....@@ -1179,18 +1171,16 @@
11791171 }
11801172 EXPORT_SYMBOL_GPL(rhashtable_destroy);
11811173 
1182
-struct rhash_head __rcu **rht_bucket_nested(const struct bucket_table *tbl,
1183
-					    unsigned int hash)
1174
+struct rhash_lock_head __rcu **__rht_bucket_nested(
1175
+	const struct bucket_table *tbl, unsigned int hash)
11841176 {
11851177 	const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
1186
-	static struct rhash_head __rcu *rhnull =
1187
-		(struct rhash_head __rcu *)NULLS_MARKER(0);
11881178 	unsigned int index = hash & ((1 << tbl->nest) - 1);
11891179 	unsigned int size = tbl->size >> tbl->nest;
11901180 	unsigned int subhash = hash;
11911181 	union nested_table *ntbl;
11921182 
1193
-	ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
1183
+	ntbl = nested_table_top(tbl);
11941184 	ntbl = rht_dereference_bucket_rcu(ntbl[index].table, tbl, hash);
11951185 	subhash >>= tbl->nest;
11961186 
....@@ -1203,23 +1193,33 @@
12031193 	}
12041194 
12051195 	if (!ntbl)
1206
-		return &rhnull;
1196
+		return NULL;
12071197 
12081198 	return &ntbl[subhash].bucket;
12091199 
12101200 }
1201
+EXPORT_SYMBOL_GPL(__rht_bucket_nested);
1202
+
1203
+struct rhash_lock_head __rcu **rht_bucket_nested(
1204
+	const struct bucket_table *tbl, unsigned int hash)
1205
+{
1206
+	static struct rhash_lock_head __rcu *rhnull;
1207
+
1208
+	if (!rhnull)
1209
+		INIT_RHT_NULLS_HEAD(rhnull);
1210
+	return __rht_bucket_nested(tbl, hash) ?: &rhnull;
1211
+}
12111212 EXPORT_SYMBOL_GPL(rht_bucket_nested);
12121213 
1213
-struct rhash_head __rcu **rht_bucket_nested_insert(struct rhashtable *ht,
1214
-						   struct bucket_table *tbl,
1215
-						   unsigned int hash)
1214
+struct rhash_lock_head __rcu **rht_bucket_nested_insert(
1215
+	struct rhashtable *ht, struct bucket_table *tbl, unsigned int hash)
12161216 {
12171217 	const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
12181218 	unsigned int index = hash & ((1 << tbl->nest) - 1);
12191219 	unsigned int size = tbl->size >> tbl->nest;
12201220 	union nested_table *ntbl;
12211221 
1222
-	ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
1222
+	ntbl = nested_table_top(tbl);
12231223 	hash >>= tbl->nest;
12241224 	ntbl = nested_table_alloc(ht, &ntbl[index].table,
12251225 				  size <= (1 << shift));