diff options
| -rw-r--r-- | include/linux/rhashtable.h | 19 | ||||
| -rw-r--r-- | lib/rhashtable.c | 284 |
2 files changed, 3 insertions, 300 deletions
diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h index a7188eeb135b..c3034de2c235 100644 --- a/include/linux/rhashtable.h +++ b/include/linux/rhashtable.h @@ -1,14 +1,13 @@ /* * Resizable, Scalable, Concurrent Hash Table * + * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au> * Copyright (c) 2014 Thomas Graf <tgraf@suug.ch> * Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net> * - * Based on the following paper by Josh Triplett, Paul E. McKenney - * and Jonathan Walpole: - * https://www.usenix.org/legacy/event/atc11/tech/final_files/Triplett.pdf - * * Code partially derived from nft_hash + * Rewritten with rehash code from br_multicast plus single list + * pointer as suggested by Josh Triplett * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as @@ -282,22 +281,10 @@ int rhashtable_init(struct rhashtable *ht, int rhashtable_insert_slow(struct rhashtable *ht, const void *key, struct rhash_head *obj, struct bucket_table *old_tbl); -void rhashtable_insert(struct rhashtable *ht, struct rhash_head *node); -bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *node); int rhashtable_expand(struct rhashtable *ht); int rhashtable_shrink(struct rhashtable *ht); -void *rhashtable_lookup(struct rhashtable *ht, const void *key); -void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key, - bool (*compare)(void *, void *), void *arg); - -bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj); -bool rhashtable_lookup_compare_insert(struct rhashtable *ht, - struct rhash_head *obj, - bool (*compare)(void *, void *), - void *arg); - int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter); void rhashtable_walk_exit(struct rhashtable_iter *iter); int rhashtable_walk_start(struct rhashtable_iter *iter) __acquires(RCU); diff --git a/lib/rhashtable.c b/lib/rhashtable.c index d1d23fb58525..83cfedd6612a 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -339,290 +339,6 @@ exit: } EXPORT_SYMBOL_GPL(rhashtable_insert_slow); -static bool __rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj, - bool (*compare)(void *, void *), void *arg) -{ - struct bucket_table *tbl, *old_tbl; - struct rhash_head *head; - bool no_resize_running; - unsigned hash; - spinlock_t *old_lock; - bool success = true; - - rcu_read_lock(); - - old_tbl = rht_dereference_rcu(ht->tbl, ht); - hash = head_hashfn(ht, old_tbl, obj); - old_lock = rht_bucket_lock(old_tbl, hash); - - spin_lock_bh(old_lock); - - /* Because we have already taken the bucket lock in old_tbl, - * if we find that future_tbl is not yet visible then that - * guarantees all other insertions of the same entry will - * also grab the bucket lock in old_tbl because until the - * rehash completes ht->tbl won't be changed. - */ - tbl = rht_dereference_rcu(old_tbl->future_tbl, ht) ?: old_tbl; - if (tbl != old_tbl) { - hash = head_hashfn(ht, tbl, obj); - spin_lock_nested(rht_bucket_lock(tbl, hash), - SINGLE_DEPTH_NESTING); - } - - if (compare && - rhashtable_lookup_compare(ht, rht_obj(ht, obj) + ht->p.key_offset, - compare, arg)) { - success = false; - goto exit; - } - - no_resize_running = tbl == old_tbl; - - head = rht_dereference_bucket(tbl->buckets[hash], tbl, hash); - - if (rht_is_a_nulls(head)) - INIT_RHT_NULLS_HEAD(obj->next, ht, hash); - else - RCU_INIT_POINTER(obj->next, head); - - rcu_assign_pointer(tbl->buckets[hash], obj); - - atomic_inc(&ht->nelems); - if (no_resize_running && rht_grow_above_75(ht, tbl)) - schedule_work(&ht->run_work); - -exit: - if (tbl != old_tbl) - spin_unlock(rht_bucket_lock(tbl, hash)); - - spin_unlock_bh(old_lock); - - rcu_read_unlock(); - - return success; -} - -/** - * rhashtable_insert - insert object into hash table - * @ht: hash table - * @obj: pointer to hash head inside object - * - * Will take a per bucket spinlock to protect against mutual mutations - * on the same bucket. Multiple insertions may occur in parallel unless - * they map to the same bucket lock. - * - * It is safe to call this function from atomic context. - * - * Will trigger an automatic deferred table resizing if the size grows - * beyond the watermark indicated by grow_decision() which can be passed - * to rhashtable_init(). - */ -void rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj) -{ - __rhashtable_insert(ht, obj, NULL, NULL); -} -EXPORT_SYMBOL_GPL(rhashtable_insert); - -static bool __rhashtable_remove(struct rhashtable *ht, - struct bucket_table *tbl, - struct rhash_head *obj) -{ - struct rhash_head __rcu **pprev; - struct rhash_head *he; - spinlock_t * lock; - unsigned hash; - bool ret = false; - - hash = head_hashfn(ht, tbl, obj); - lock = rht_bucket_lock(tbl, hash); - - spin_lock_bh(lock); - - pprev = &tbl->buckets[hash]; - rht_for_each(he, tbl, hash) { - if (he != obj) { - pprev = &he->next; - continue; - } - - rcu_assign_pointer(*pprev, obj->next); - ret = true; - break; - } - - spin_unlock_bh(lock); - - return ret; -} - -/** - * rhashtable_remove - remove object from hash table - * @ht: hash table - * @obj: pointer to hash head inside object - * - * Since the hash chain is single linked, the removal operation needs to - * walk the bucket chain upon removal. The removal operation is thus - * considerable slow if the hash table is not correctly sized. - * - * Will automatically shrink the table via rhashtable_expand() if the - * shrink_decision function specified at rhashtable_init() returns true. - * - * The caller must ensure that no concurrent table mutations occur. It is - * however valid to have concurrent lookups if they are RCU protected. - */ -bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *obj) -{ - struct bucket_table *tbl; - bool ret; - - rcu_read_lock(); - - tbl = rht_dereference_rcu(ht->tbl, ht); - - /* Because we have already taken (and released) the bucket - * lock in old_tbl, if we find that future_tbl is not yet - * visible then that guarantees the entry to still be in - * the old tbl if it exists. - */ - while (!(ret = __rhashtable_remove(ht, tbl, obj)) && - (tbl = rht_dereference_rcu(tbl->future_tbl, ht))) - ; - - if (ret) { - atomic_dec(&ht->nelems); - if (rht_shrink_below_30(ht, tbl)) - schedule_work(&ht->run_work); - } - - rcu_read_unlock(); - - return ret; -} -EXPORT_SYMBOL_GPL(rhashtable_remove); - -/** - * rhashtable_lookup - lookup key in hash table - * @ht: hash table - * @key: pointer to key - * - * Computes the hash value for the key and traverses the bucket chain looking - * for a entry with an identical key. The first matching entry is returned. - * - * This lookup function may only be used for fixed key hash table (key_len - * parameter set). It will BUG() if used inappropriately. - * - * Lookups may occur in parallel with hashtable mutations and resizing. - */ -void *rhashtable_lookup(struct rhashtable *ht, const void *key) -{ - return rhashtable_lookup_fast(ht, key, ht->p); -} -EXPORT_SYMBOL_GPL(rhashtable_lookup); - -/** - * rhashtable_lookup_compare - search hash table with compare function - * @ht: hash table - * @key: the pointer to the key - * @compare: compare function, must return true on match - * @arg: argument passed on to compare function - * - * Traverses the bucket chain behind the provided hash value and calls the - * specified compare function for each entry. - * - * Lookups may occur in parallel with hashtable mutations and resizing. - * - * Returns the first entry on which the compare function returned true. - */ -void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key, - bool (*compare)(void *, void *), - void *arg) -{ - const struct bucket_table *tbl; - struct rhash_head *he; - u32 hash; - - rcu_read_lock(); - - tbl = rht_dereference_rcu(ht->tbl, ht); -restart: - hash = rht_key_hashfn(ht, tbl, key, ht->p); - rht_for_each_rcu(he, tbl, hash) { - if (!compare(rht_obj(ht, he), arg)) - continue; - rcu_read_unlock(); - return rht_obj(ht, he); - } - - /* Ensure we see any new tables. */ - smp_rmb(); - - tbl = rht_dereference_rcu(tbl->future_tbl, ht); - if (unlikely(tbl)) - goto restart; - rcu_read_unlock(); - - return NULL; -} -EXPORT_SYMBOL_GPL(rhashtable_lookup_compare); - -/** - * rhashtable_lookup_insert - lookup and insert object into hash table - * @ht: hash table - * @obj: pointer to hash head inside object - * - * Locks down the bucket chain in both the old and new table if a resize - * is in progress to ensure that writers can't remove from the old table - * and can't insert to the new table during the atomic operation of search - * and insertion. Searches for duplicates in both the old and new table if - * a resize is in progress. - * - * This lookup function may only be used for fixed key hash table (key_len - * parameter set). It will BUG() if used inappropriately. - * - * It is safe to call this function from atomic context. - * - * Will trigger an automatic deferred table resizing if the size grows - * beyond the watermark indicated by grow_decision() which can be passed - * to rhashtable_init(). - */ -bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj) -{ - return rhashtable_lookup_insert_fast(ht, obj, ht->p); -} -EXPORT_SYMBOL_GPL(rhashtable_lookup_insert); - -/** - * rhashtable_lookup_compare_insert - search and insert object to hash table - * with compare function - * @ht: hash table - * @obj: pointer to hash head inside object - * @compare: compare function, must return true on match - * @arg: argument passed on to compare function - * - * Locks down the bucket chain in both the old and new table if a resize - * is in progress to ensure that writers can't remove from the old table - * and can't insert to the new table during the atomic operation of search - * and insertion. Searches for duplicates in both the old and new table if - * a resize is in progress. - * - * Lookups may occur in parallel with hashtable mutations and resizing. - * - * Will trigger an automatic deferred table resizing if the size grows - * beyond the watermark indicated by grow_decision() which can be passed - * to rhashtable_init(). - */ -bool rhashtable_lookup_compare_insert(struct rhashtable *ht, - struct rhash_head *obj, - bool (*compare)(void *, void *), - void *arg) -{ - BUG_ON(!ht->p.key_len); - - return __rhashtable_insert(ht, obj, compare, arg); -} -EXPORT_SYMBOL_GPL(rhashtable_lookup_compare_insert); - /** * rhashtable_walk_init - Initialise an iterator * @ht: Table to walk over |