--- /dev/null
+/*
+ * Resizable, Scalable, Concurrent Hash Table
+ *
+ * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>
+ * Copyright (c) 2014-2015 Thomas Graf <tgraf@suug.ch>
+ * Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net>
+ *
+ * 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
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/atomic.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/log2.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/mm.h>
+#include <linux/jhash.h>
+#include <linux/random.h>
+#include <linux/err.h>
+#include <linux/export.h>
+
+#define HASH_DEFAULT_SIZE 64UL
+#define HASH_MIN_SIZE 4U
+#define BUCKET_LOCKS_PER_CPU 128UL
+
+static u32 head_hashfn(struct rhashtable *ht,
+ const struct bucket_table *tbl,
+ const struct rhash_head *he)
+{
+ return rht_head_hashfn(ht, tbl, he, ht->p);
+}
+
+#ifdef CONFIG_PROVE_LOCKING
+#define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT))
+
+int lockdep_rht_mutex_is_held(struct rhashtable *ht)
+{
+ return (debug_locks) ? lockdep_is_held(&ht->mutex) : 1;
+}
+
+int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash)
+{
+ spinlock_t *lock = rht_bucket_lock(tbl, hash);
+
+ return (debug_locks) ? lockdep_is_held(lock) : 1;
+}
+#else
+#define ASSERT_RHT_MUTEX(HT)
+#endif
+
+
+static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl,
+ gfp_t gfp)
+{
+ unsigned int i, size;
+#if defined(CONFIG_PROVE_LOCKING)
+ unsigned int nr_pcpus = 2;
+#else
+ unsigned int nr_pcpus = num_possible_cpus();
+#endif
+
+ nr_pcpus = min_t(unsigned int, nr_pcpus, 32UL);
+ size = roundup_pow_of_two(nr_pcpus * ht->p.locks_mul);
+
+ /* Never allocate more than 0.5 locks per bucket */
+ size = min_t(unsigned int, size, tbl->size >> 1);
+
+ if (sizeof(spinlock_t) != 0) {
+#ifdef CONFIG_NUMA
+ if (size * sizeof(spinlock_t) > PAGE_SIZE &&
+ gfp == GFP_KERNEL)
+ tbl->locks = vmalloc(size * sizeof(spinlock_t));
+ else
+#endif
+ tbl->locks = kmalloc_array(size, sizeof(spinlock_t),
+ gfp);
+ if (!tbl->locks)
+ return -ENOMEM;
+ for (i = 0; i < size; i++)
+ spin_lock_init(&tbl->locks[i]);
+ }
+ tbl->locks_mask = size - 1;
+
+ return 0;
+}
+
+static void bucket_table_free(const struct bucket_table *tbl)
+{
+ if (tbl)
+ kvfree(tbl->locks);
+
+ kvfree(tbl);
+}
+
+static void bucket_table_free_rcu(struct rcu_head *head)
+{
+ bucket_table_free(container_of(head, struct bucket_table, rcu));
+}
+
+static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
+ size_t nbuckets,
+ gfp_t gfp)
+{
+ struct bucket_table *tbl = NULL;
+ size_t size;
+ int i;
+
+ size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]);
+ if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER) ||
+ gfp != GFP_KERNEL)
+ tbl = kzalloc(size, gfp | __GFP_NOWARN | __GFP_NORETRY);
+ if (tbl == NULL && gfp == GFP_KERNEL)
+ tbl = vzalloc(size);
+ if (tbl == NULL)
+ return NULL;
+
+ tbl->size = nbuckets;
+
+ if (alloc_bucket_locks(ht, tbl, gfp) < 0) {
+ bucket_table_free(tbl);
+ return NULL;
+ }
+
+ INIT_LIST_HEAD(&tbl->walkers);
+
+ get_random_bytes(&tbl->hash_rnd, sizeof(tbl->hash_rnd));
+
+ for (i = 0; i < nbuckets; i++)
+ INIT_RHT_NULLS_HEAD(tbl->buckets[i], ht, i);
+
+ return tbl;
+}
+
+static struct bucket_table *rhashtable_last_table(struct rhashtable *ht,
+ struct bucket_table *tbl)
+{
+ struct bucket_table *new_tbl;
+
+ do {
+ new_tbl = tbl;
+ tbl = rht_dereference_rcu(tbl->future_tbl, ht);
+ } while (tbl);
+
+ return new_tbl;
+}
+
+static int rhashtable_rehash_one(struct rhashtable *ht, unsigned int old_hash)
+{
+ struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
+ struct bucket_table *new_tbl = rhashtable_last_table(ht,
+ rht_dereference_rcu(old_tbl->future_tbl, ht));
+ struct rhash_head __rcu **pprev = &old_tbl->buckets[old_hash];
+ int err = -ENOENT;
+ struct rhash_head *head, *next, *entry;
+ spinlock_t *new_bucket_lock;
+ unsigned int new_hash;
+
+ rht_for_each(entry, old_tbl, old_hash) {
+ err = 0;
+ next = rht_dereference_bucket(entry->next, old_tbl, old_hash);
+
+ if (rht_is_a_nulls(next))
+ break;
+
+ pprev = &entry->next;
+ }
+
+ if (err)
+ goto out;
+
+ new_hash = head_hashfn(ht, new_tbl, entry);
+
+ new_bucket_lock = rht_bucket_lock(new_tbl, new_hash);
+
+ spin_lock_nested(new_bucket_lock, SINGLE_DEPTH_NESTING);
+ head = rht_dereference_bucket(new_tbl->buckets[new_hash],
+ new_tbl, new_hash);
+
+ RCU_INIT_POINTER(entry->next, head);
+
+ rcu_assign_pointer(new_tbl->buckets[new_hash], entry);
+ spin_unlock(new_bucket_lock);
+
+ rcu_assign_pointer(*pprev, next);
+
+out:
+ return err;
+}
+
+static void rhashtable_rehash_chain(struct rhashtable *ht,
+ unsigned int old_hash)
+{
+ struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
+ spinlock_t *old_bucket_lock;
+
+ old_bucket_lock = rht_bucket_lock(old_tbl, old_hash);
+
+ spin_lock_bh(old_bucket_lock);
+ while (!rhashtable_rehash_one(ht, old_hash))
+ ;
+ old_tbl->rehash++;
+ spin_unlock_bh(old_bucket_lock);
+}
+
+static int rhashtable_rehash_attach(struct rhashtable *ht,
+ struct bucket_table *old_tbl,
+ struct bucket_table *new_tbl)
+{
+ /* Protect future_tbl using the first bucket lock. */
+ spin_lock_bh(old_tbl->locks);
+
+ /* Did somebody beat us to it? */
+ if (rcu_access_pointer(old_tbl->future_tbl)) {
+ spin_unlock_bh(old_tbl->locks);
+ return -EEXIST;
+ }
+
+ /* Make insertions go into the new, empty table right away. Deletions
+ * and lookups will be attempted in both tables until we synchronize.
+ */
+ rcu_assign_pointer(old_tbl->future_tbl, new_tbl);
+
+ /* Ensure the new table is visible to readers. */
+ smp_wmb();
+
+ spin_unlock_bh(old_tbl->locks);
+
+ return 0;
+}
+
+static int rhashtable_rehash_table(struct rhashtable *ht)
+{
+ struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
+ struct bucket_table *new_tbl;
+ struct rhashtable_walker *walker;
+ unsigned int old_hash;
+
+ new_tbl = rht_dereference(old_tbl->future_tbl, ht);
+ if (!new_tbl)
+ return 0;
+
+ for (old_hash = 0; old_hash < old_tbl->size; old_hash++)
+ rhashtable_rehash_chain(ht, old_hash);
+
+ /* Publish the new table pointer. */
+ rcu_assign_pointer(ht->tbl, new_tbl);
+
+ spin_lock(&ht->lock);
+ list_for_each_entry(walker, &old_tbl->walkers, list)
+ walker->tbl = NULL;
+ spin_unlock(&ht->lock);
+
+ /* Wait for readers. All new readers will see the new
+ * table, and thus no references to the old table will
+ * remain.
+ */
+ call_rcu(&old_tbl->rcu, bucket_table_free_rcu);
+
+ return rht_dereference(new_tbl->future_tbl, ht) ? -EAGAIN : 0;
+}
+
+/**
+ * rhashtable_expand - Expand hash table while allowing concurrent lookups
+ * @ht: the hash table to expand
+ *
+ * A secondary bucket array is allocated and the hash entries are migrated.
+ *
+ * This function may only be called in a context where it is safe to call
+ * synchronize_rcu(), e.g. not within a rcu_read_lock() section.
+ *
+ * The caller must ensure that no concurrent resizing occurs by holding
+ * ht->mutex.
+ *
+ * It is valid to have concurrent insertions and deletions protected by per
+ * bucket locks or concurrent RCU protected lookups and traversals.
+ */
+static int rhashtable_expand(struct rhashtable *ht)
+{
+ struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht);
+ int err;
+
+ ASSERT_RHT_MUTEX(ht);
+
+ old_tbl = rhashtable_last_table(ht, old_tbl);
+
+ new_tbl = bucket_table_alloc(ht, old_tbl->size * 2, GFP_KERNEL);
+ if (new_tbl == NULL)
+ return -ENOMEM;
+
+ err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
+ if (err)
+ bucket_table_free(new_tbl);
+
+ return err;
+}
+
+/**
+ * rhashtable_shrink - Shrink hash table while allowing concurrent lookups
+ * @ht: the hash table to shrink
+ *
+ * This function shrinks the hash table to fit, i.e., the smallest
+ * size would not cause it to expand right away automatically.
+ *
+ * The caller must ensure that no concurrent resizing occurs by holding
+ * ht->mutex.
+ *
+ * The caller must ensure that no concurrent table mutations take place.
+ * It is however valid to have concurrent lookups if they are RCU protected.
+ *
+ * It is valid to have concurrent insertions and deletions protected by per
+ * bucket locks or concurrent RCU protected lookups and traversals.
+ */
+static int rhashtable_shrink(struct rhashtable *ht)
+{
+ struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht);
+ unsigned int size;
+ int err;
+
+ ASSERT_RHT_MUTEX(ht);
+
+ size = roundup_pow_of_two(atomic_read(&ht->nelems) * 3 / 2);
+ if (size < ht->p.min_size)
+ size = ht->p.min_size;
+
+ if (old_tbl->size <= size)
+ return 0;
+
+ if (rht_dereference(old_tbl->future_tbl, ht))
+ return -EEXIST;
+
+ new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
+ if (new_tbl == NULL)
+ return -ENOMEM;
+
+ err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
+ if (err)
+ bucket_table_free(new_tbl);
+
+ return err;
+}
+
+static void rht_deferred_worker(struct work_struct *work)
+{
+ struct rhashtable *ht;
+ struct bucket_table *tbl;
+ int err = 0;
+
+ ht = container_of(work, struct rhashtable, run_work);
+ mutex_lock(&ht->mutex);
+
+ tbl = rht_dereference(ht->tbl, ht);
+ tbl = rhashtable_last_table(ht, tbl);
+
+ if (rht_grow_above_75(ht, tbl))
+ rhashtable_expand(ht);
+ else if (ht->p.automatic_shrinking && rht_shrink_below_30(ht, tbl))
+ rhashtable_shrink(ht);
+
+ err = rhashtable_rehash_table(ht);
+
+ mutex_unlock(&ht->mutex);
+
+ if (err)
+ schedule_work(&ht->run_work);
+}
+
+static bool rhashtable_check_elasticity(struct rhashtable *ht,
+ struct bucket_table *tbl,
+ unsigned int hash)
+{
+ unsigned int elasticity = ht->elasticity;
+ struct rhash_head *head;
+
+ rht_for_each(head, tbl, hash)
+ if (!--elasticity)
+ return true;
+
+ return false;
+}
+
+int rhashtable_insert_rehash(struct rhashtable *ht,
+ struct bucket_table *tbl)
+{
+ struct bucket_table *old_tbl;
+ struct bucket_table *new_tbl;
+ unsigned int size;
+ int err;
+
+ old_tbl = rht_dereference_rcu(ht->tbl, ht);
+
+ size = tbl->size;
+
+ err = -EBUSY;
+
+ if (rht_grow_above_75(ht, tbl))
+ size *= 2;
+ /* Do not schedule more than one rehash */
+ else if (old_tbl != tbl)
+ goto fail;
+
+ err = -ENOMEM;
+
+ new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC);
+ if (new_tbl == NULL)
+ goto fail;
+
+ err = rhashtable_rehash_attach(ht, tbl, new_tbl);
+ if (err) {
+ bucket_table_free(new_tbl);
+ if (err == -EEXIST)
+ err = 0;
+ } else
+ schedule_work(&ht->run_work);
+
+ return err;
+
+fail:
+ /* Do not fail the insert if someone else did a rehash. */
+ if (likely(rcu_dereference_raw(tbl->future_tbl)))
+ return 0;
+
+ /* Schedule async rehash to retry allocation in process context. */
+ if (err == -ENOMEM)
+ schedule_work(&ht->run_work);
+
+ return err;
+}
+
+struct bucket_table *rhashtable_insert_slow(struct rhashtable *ht,
+ const void *key,
+ struct rhash_head *obj,
+ struct bucket_table *tbl)
+{
+ struct rhash_head *head;
+ unsigned int hash;
+ int err;
+
+ tbl = rhashtable_last_table(ht, tbl);
+ hash = head_hashfn(ht, tbl, obj);
+ spin_lock_nested(rht_bucket_lock(tbl, hash), SINGLE_DEPTH_NESTING);
+
+ err = -EEXIST;
+ if (key && rhashtable_lookup_fast(ht, key, ht->p))
+ goto exit;
+
+ err = -E2BIG;
+ if (unlikely(rht_grow_above_max(ht, tbl)))
+ goto exit;
+
+ err = -EAGAIN;
+ if (rhashtable_check_elasticity(ht, tbl, hash) ||
+ rht_grow_above_100(ht, tbl))
+ goto exit;
+
+ err = 0;
+
+ head = rht_dereference_bucket(tbl->buckets[hash], tbl, hash);
+
+ RCU_INIT_POINTER(obj->next, head);
+
+ rcu_assign_pointer(tbl->buckets[hash], obj);
+
+ atomic_inc(&ht->nelems);
+
+exit:
+ spin_unlock(rht_bucket_lock(tbl, hash));
+
+ if (err == 0)
+ return NULL;
+ else if (err == -EAGAIN)
+ return tbl;
+ else
+ return ERR_PTR(err);
+}
+
+/**
+ * rhashtable_walk_init - Initialise an iterator
+ * @ht: Table to walk over
+ * @iter: Hash table Iterator
+ *
+ * This function prepares a hash table walk.
+ *
+ * Note that if you restart a walk after rhashtable_walk_stop you
+ * may see the same object twice. Also, you may miss objects if
+ * there are removals in between rhashtable_walk_stop and the next
+ * call to rhashtable_walk_start.
+ *
+ * For a completely stable walk you should construct your own data
+ * structure outside the hash table.
+ *
+ * This function may sleep so you must not call it from interrupt
+ * context or with spin locks held.
+ *
+ * You must call rhashtable_walk_exit if this function returns
+ * successfully.
+ */
+int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter)
+{
+ iter->ht = ht;
+ iter->p = NULL;
+ iter->slot = 0;
+ iter->skip = 0;
+
+ iter->walker = kmalloc(sizeof(*iter->walker), GFP_KERNEL);
+ if (!iter->walker)
+ return -ENOMEM;
+
+ spin_lock(&ht->lock);
+ iter->walker->tbl =
+ rcu_dereference_protected(ht->tbl, lockdep_is_held(&ht->lock));
+ list_add(&iter->walker->list, &iter->walker->tbl->walkers);
+ spin_unlock(&ht->lock);
+
+ return 0;
+}
+
+/**
+ * rhashtable_walk_exit - Free an iterator
+ * @iter: Hash table Iterator
+ *
+ * This function frees resources allocated by rhashtable_walk_init.
+ */
+void rhashtable_walk_exit(struct rhashtable_iter *iter)
+{
+ spin_lock(&iter->ht->lock);
+ if (iter->walker->tbl)
+ list_del(&iter->walker->list);
+ spin_unlock(&iter->ht->lock);
+ kfree(iter->walker);
+}
+
+/**
+ * rhashtable_walk_start - Start a hash table walk
+ * @iter: Hash table iterator
+ *
+ * Start a hash table walk. Note that we take the RCU lock in all
+ * cases including when we return an error. So you must always call
+ * rhashtable_walk_stop to clean up.
+ *
+ * Returns zero if successful.
+ *
+ * Returns -EAGAIN if resize event occured. Note that the iterator
+ * will rewind back to the beginning and you may use it immediately
+ * by calling rhashtable_walk_next.
+ */
+int rhashtable_walk_start(struct rhashtable_iter *iter)
+ __acquires(RCU)
+{
+ struct rhashtable *ht = iter->ht;
+
+ rcu_read_lock();
+
+ spin_lock(&ht->lock);
+ if (iter->walker->tbl)
+ list_del(&iter->walker->list);
+ spin_unlock(&ht->lock);
+
+ if (!iter->walker->tbl) {
+ iter->walker->tbl = rht_dereference_rcu(ht->tbl, ht);
+ return -EAGAIN;
+ }
+
+ return 0;
+}
+
+/**
+ * rhashtable_walk_next - Return the next object and advance the iterator
+ * @iter: Hash table iterator
+ *
+ * Note that you must call rhashtable_walk_stop when you are finished
+ * with the walk.
+ *
+ * Returns the next object or NULL when the end of the table is reached.
+ *
+ * Returns -EAGAIN if resize event occured. Note that the iterator
+ * will rewind back to the beginning and you may continue to use it.
+ */
+void *rhashtable_walk_next(struct rhashtable_iter *iter)
+{
+ struct bucket_table *tbl = iter->walker->tbl;
+ struct rhashtable *ht = iter->ht;
+ struct rhash_head *p = iter->p;
+
+ if (p) {
+ p = rht_dereference_bucket_rcu(p->next, tbl, iter->slot);
+ goto next;
+ }
+
+ for (; iter->slot < tbl->size; iter->slot++) {
+ int skip = iter->skip;
+
+ rht_for_each_rcu(p, tbl, iter->slot) {
+ if (!skip)
+ break;
+ skip--;
+ }
+
+next:
+ if (!rht_is_a_nulls(p)) {
+ iter->skip++;
+ iter->p = p;
+ return rht_obj(ht, p);
+ }
+
+ iter->skip = 0;
+ }
+
+ iter->p = NULL;
+
+ /* Ensure we see any new tables. */
+ smp_rmb();
+
+ iter->walker->tbl = rht_dereference_rcu(tbl->future_tbl, ht);
+ if (iter->walker->tbl) {
+ iter->slot = 0;
+ iter->skip = 0;
+ return ERR_PTR(-EAGAIN);
+ }
+
+ return NULL;
+}
+
+/**
+ * rhashtable_walk_stop - Finish a hash table walk
+ * @iter: Hash table iterator
+ *
+ * Finish a hash table walk.
+ */
+void rhashtable_walk_stop(struct rhashtable_iter *iter)
+ __releases(RCU)
+{
+ struct rhashtable *ht;
+ struct bucket_table *tbl = iter->walker->tbl;
+
+ if (!tbl)
+ goto out;
+
+ ht = iter->ht;
+
+ spin_lock(&ht->lock);
+ if (tbl->rehash < tbl->size)
+ list_add(&iter->walker->list, &tbl->walkers);
+ else
+ iter->walker->tbl = NULL;
+ spin_unlock(&ht->lock);
+
+ iter->p = NULL;
+
+out:
+ rcu_read_unlock();
+}
+
+static size_t rounded_hashtable_size(const struct rhashtable_params *params)
+{
+ return max(roundup_pow_of_two(params->nelem_hint * 4 / 3),
+ (unsigned long)params->min_size);
+}
+
+static u32 rhashtable_jhash2(const void *key, u32 length, u32 seed)
+{
+ return jhash2(key, length, seed);
+}
+
+/**
+ * rhashtable_init - initialize a new hash table
+ * @ht: hash table to be initialized
+ * @params: configuration parameters
+ *
+ * Initializes a new hash table based on the provided configuration
+ * parameters. A table can be configured either with a variable or
+ * fixed length key:
+ *
+ * Configuration Example 1: Fixed length keys
+ * struct test_obj {
+ * int key;
+ * void * my_member;
+ * struct rhash_head node;
+ * };
+ *
+ * struct rhashtable_params params = {
+ * .head_offset = offsetof(struct test_obj, node),
+ * .key_offset = offsetof(struct test_obj, key),
+ * .key_len = sizeof(int),
+ * .hashfn = jhash,
+ * .nulls_base = (1U << RHT_BASE_SHIFT),
+ * };
+ *
+ * Configuration Example 2: Variable length keys
+ * struct test_obj {
+ * [...]
+ * struct rhash_head node;
+ * };
+ *
+ * u32 my_hash_fn(const void *data, u32 len, u32 seed)
+ * {
+ * struct test_obj *obj = data;
+ *
+ * return [... hash ...];
+ * }
+ *
+ * struct rhashtable_params params = {
+ * .head_offset = offsetof(struct test_obj, node),
+ * .hashfn = jhash,
+ * .obj_hashfn = my_hash_fn,
+ * };
+ */
+int rhashtable_init(struct rhashtable *ht,
+ const struct rhashtable_params *params)
+{
+ struct bucket_table *tbl;
+ size_t size;
+
+ size = HASH_DEFAULT_SIZE;
+
+ if ((!params->key_len && !params->obj_hashfn) ||
+ (params->obj_hashfn && !params->obj_cmpfn))
+ return -EINVAL;
+
+ if (params->nulls_base && params->nulls_base < (1U << RHT_BASE_SHIFT))
+ return -EINVAL;
+
+ memset(ht, 0, sizeof(*ht));
+ mutex_init(&ht->mutex);
+ spin_lock_init(&ht->lock);
+ memcpy(&ht->p, params, sizeof(*params));
+
+ if (params->min_size)
+ ht->p.min_size = roundup_pow_of_two(params->min_size);
+
+ if (params->max_size)
+ ht->p.max_size = rounddown_pow_of_two(params->max_size);
+
+ if (params->insecure_max_entries)
+ ht->p.insecure_max_entries =
+ rounddown_pow_of_two(params->insecure_max_entries);
+ else
+ ht->p.insecure_max_entries = ht->p.max_size * 2;
+
+ ht->p.min_size = max(ht->p.min_size, HASH_MIN_SIZE);
+
+ if (params->nelem_hint)
+ size = rounded_hashtable_size(&ht->p);
+
+ /* The maximum (not average) chain length grows with the
+ * size of the hash table, at a rate of (log N)/(log log N).
+ * The value of 16 is selected so that even if the hash
+ * table grew to 2^32 you would not expect the maximum
+ * chain length to exceed it unless we are under attack
+ * (or extremely unlucky).
+ *
+ * As this limit is only to detect attacks, we don't need
+ * to set it to a lower value as you'd need the chain
+ * length to vastly exceed 16 to have any real effect
+ * on the system.
+ */
+ if (!params->insecure_elasticity)
+ ht->elasticity = 16;
+
+ if (params->locks_mul)
+ ht->p.locks_mul = roundup_pow_of_two(params->locks_mul);
+ else
+ ht->p.locks_mul = BUCKET_LOCKS_PER_CPU;
+
+ ht->key_len = ht->p.key_len;
+ if (!params->hashfn) {
+ ht->p.hashfn = jhash;
+
+ if (!(ht->key_len & (sizeof(u32) - 1))) {
+ ht->key_len /= sizeof(u32);
+ ht->p.hashfn = rhashtable_jhash2;
+ }
+ }
+
+ tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
+ if (tbl == NULL)
+ return -ENOMEM;
+
+ atomic_set(&ht->nelems, 0);
+
+ RCU_INIT_POINTER(ht->tbl, tbl);
+
+ INIT_WORK(&ht->run_work, rht_deferred_worker);
+
+ return 0;
+}
+
+/**
+ * rhashtable_free_and_destroy - free elements and destroy hash table
+ * @ht: the hash table to destroy
+ * @free_fn: callback to release resources of element
+ * @arg: pointer passed to free_fn
+ *
+ * Stops an eventual async resize. If defined, invokes free_fn for each
+ * element to releasal resources. Please note that RCU protected
+ * readers may still be accessing the elements. Releasing of resources
+ * must occur in a compatible manner. Then frees the bucket array.
+ *
+ * This function will eventually sleep to wait for an async resize
+ * to complete. The caller is responsible that no further write operations
+ * occurs in parallel.
+ */
+void rhashtable_free_and_destroy(struct rhashtable *ht,
+ void (*free_fn)(void *ptr, void *arg),
+ void *arg)
+{
+ const struct bucket_table *tbl;
+ unsigned int i;
+
+ cancel_work_sync(&ht->run_work);
+
+ mutex_lock(&ht->mutex);
+ tbl = rht_dereference(ht->tbl, ht);
+ if (free_fn) {
+ for (i = 0; i < tbl->size; i++) {
+ struct rhash_head *pos, *next;
+
+ for (pos = rht_dereference(tbl->buckets[i], ht),
+ next = !rht_is_a_nulls(pos) ?
+ rht_dereference(pos->next, ht) : NULL;
+ !rht_is_a_nulls(pos);
+ pos = next,
+ next = !rht_is_a_nulls(pos) ?
+ rht_dereference(pos->next, ht) : NULL)
+ free_fn(rht_obj(ht, pos), arg);
+ }
+ }
+
+ bucket_table_free(tbl);
+ mutex_unlock(&ht->mutex);
+}
+
+void rhashtable_destroy(struct rhashtable *ht)
+{
+ return rhashtable_free_and_destroy(ht, NULL, NULL);
+}
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