/*
* 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
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);
}
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
git.openpandora.org / pandora-kernel.git / commitdiff