#include <linux/list_nulls.h>
#include <linux/workqueue.h>
#include <linux/mutex.h>
+#include <linux/rcupdate.h>
/*
* The end of the chain is marked with a special nulls marks which has
#define RHT_HASH_BITS 27
#define RHT_BASE_SHIFT RHT_HASH_BITS
+/* Base bits plus 1 bit for nulls marker */
+#define RHT_HASH_RESERVED_SPACE (RHT_BASE_BITS + 1)
+
struct rhash_head {
struct rhash_head __rcu *next;
};
struct rhash_head __rcu *buckets[] ____cacheline_aligned_in_smp;
};
+/**
+ * struct rhashtable_compare_arg - Key for the function rhashtable_compare
+ * @ht: Hash table
+ * @key: Key to compare against
+ */
+struct rhashtable_compare_arg {
+ struct rhashtable *ht;
+ const void *key;
+};
+
typedef u32 (*rht_hashfn_t)(const void *data, u32 len, u32 seed);
typedef u32 (*rht_obj_hashfn_t)(const void *data, u32 seed);
+typedef int (*rht_obj_cmpfn_t)(struct rhashtable_compare_arg *arg,
+ const void *obj);
struct rhashtable;
* @locks_mul: Number of bucket locks to allocate per cpu (default: 128)
* @hashfn: Function to hash key
* @obj_hashfn: Function to hash object
+ * @obj_cmpfn: Function to compare key with object
*/
struct rhashtable_params {
size_t nelem_hint;
size_t locks_mul;
rht_hashfn_t hashfn;
rht_obj_hashfn_t obj_hashfn;
+ rht_obj_cmpfn_t obj_cmpfn;
};
/**
return ((unsigned long) ptr) >> 1;
}
+static inline void *rht_obj(const struct rhashtable *ht,
+ const struct rhash_head *he)
+{
+ return (char *)he - ht->p.head_offset;
+}
+
+static inline unsigned int rht_bucket_index(const struct bucket_table *tbl,
+ unsigned int hash)
+{
+ return (hash >> RHT_HASH_RESERVED_SPACE) & (tbl->size - 1);
+}
+
+static inline unsigned int rht_key_hashfn(
+ struct rhashtable *ht, const struct bucket_table *tbl,
+ const void *key, const struct rhashtable_params params)
+{
+ return rht_bucket_index(tbl, params.hashfn(key, params.key_len ?:
+ ht->p.key_len,
+ tbl->hash_rnd));
+}
+
+static inline unsigned int rht_head_hashfn(
+ struct rhashtable *ht, const struct bucket_table *tbl,
+ const struct rhash_head *he, const struct rhashtable_params params)
+{
+ const char *ptr = rht_obj(ht, he);
+
+ return likely(params.obj_hashfn) ?
+ rht_bucket_index(tbl, params.obj_hashfn(ptr, tbl->hash_rnd)) :
+ rht_key_hashfn(ht, tbl, ptr + params.key_offset, params);
+}
+
+/**
+ * rht_grow_above_75 - returns true if nelems > 0.75 * table-size
+ * @ht: hash table
+ * @tbl: current table
+ */
+static inline bool rht_grow_above_75(const struct rhashtable *ht,
+ const struct bucket_table *tbl)
+{
+ /* Expand table when exceeding 75% load */
+ return atomic_read(&ht->nelems) > (tbl->size / 4 * 3) &&
+ (!ht->p.max_size || tbl->size < ht->p.max_size);
+}
+
+/**
+ * rht_shrink_below_30 - returns true if nelems < 0.3 * table-size
+ * @ht: hash table
+ * @tbl: current table
+ */
+static inline bool rht_shrink_below_30(const struct rhashtable *ht,
+ const struct bucket_table *tbl)
+{
+ /* Shrink table beneath 30% load */
+ return atomic_read(&ht->nelems) < (tbl->size * 3 / 10) &&
+ tbl->size > ht->p.min_size;
+}
+
+/* The bucket lock is selected based on the hash and protects mutations
+ * on a group of hash buckets.
+ *
+ * A maximum of tbl->size/2 bucket locks is allocated. This ensures that
+ * a single lock always covers both buckets which may both contains
+ * entries which link to the same bucket of the old table during resizing.
+ * This allows to simplify the locking as locking the bucket in both
+ * tables during resize always guarantee protection.
+ *
+ * IMPORTANT: When holding the bucket lock of both the old and new table
+ * during expansions and shrinking, the old bucket lock must always be
+ * acquired first.
+ */
+static inline spinlock_t *rht_bucket_lock(const struct bucket_table *tbl,
+ unsigned int hash)
+{
+ return &tbl->locks[hash & tbl->locks_mask];
+}
+
#ifdef CONFIG_PROVE_LOCKING
int lockdep_rht_mutex_is_held(struct rhashtable *ht);
int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash);
int rhashtable_init(struct rhashtable *ht,
const struct rhashtable_params *params);
+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);
rht_for_each_entry_rcu_continue(tpos, pos, (tbl)->buckets[hash],\
tbl, hash, member)
+static inline int rhashtable_compare(struct rhashtable_compare_arg *arg,
+ const void *obj)
+{
+ struct rhashtable *ht = arg->ht;
+ const char *ptr = obj;
+
+ return memcmp(ptr + ht->p.key_offset, arg->key, ht->p.key_len);
+}
+
+/**
+ * rhashtable_lookup_fast - search hash table, inlined version
+ * @ht: hash table
+ * @key: the pointer to the key
+ * @params: hash table parameters
+ *
+ * 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.
+ *
+ * Returns the first entry on which the compare function returned true.
+ */
+static inline void *rhashtable_lookup_fast(
+ struct rhashtable *ht, const void *key,
+ const struct rhashtable_params params)
+{
+ struct rhashtable_compare_arg arg = {
+ .ht = ht,
+ .key = key,
+ };
+ const struct bucket_table *tbl;
+ struct rhash_head *he;
+ unsigned hash;
+
+ rcu_read_lock();
+
+ tbl = rht_dereference_rcu(ht->tbl, ht);
+restart:
+ hash = rht_key_hashfn(ht, tbl, key, params);
+ rht_for_each_rcu(he, tbl, hash) {
+ if (params.obj_cmpfn ?
+ params.obj_cmpfn(&arg, rht_obj(ht, he)) :
+ rhashtable_compare(&arg, rht_obj(ht, he)))
+ 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;
+}
+
+static inline int __rhashtable_insert_fast(
+ struct rhashtable *ht, const void *key, struct rhash_head *obj,
+ const struct rhashtable_params params)
+{
+ struct rhashtable_compare_arg arg = {
+ .ht = ht,
+ .key = key,
+ };
+ int err = -EEXIST;
+ struct bucket_table *tbl, *new_tbl;
+ struct rhash_head *head;
+ spinlock_t *lock;
+ unsigned hash;
+
+ rcu_read_lock();
+
+ tbl = rht_dereference_rcu(ht->tbl, ht);
+ hash = rht_head_hashfn(ht, tbl, obj, params);
+ lock = rht_bucket_lock(tbl, hash);
+
+ spin_lock_bh(lock);
+
+ /* Because we have already taken the bucket lock in 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 tbl because until
+ * the rehash completes ht->tbl won't be changed.
+ */
+ new_tbl = rht_dereference_rcu(tbl->future_tbl, ht);
+ if (unlikely(new_tbl)) {
+ err = rhashtable_insert_slow(ht, key, obj, new_tbl);
+ goto out;
+ }
+
+ if (!key)
+ goto skip_lookup;
+
+ rht_for_each(head, tbl, hash) {
+ if (unlikely(!(params.obj_cmpfn ?
+ params.obj_cmpfn(&arg, rht_obj(ht, head)) :
+ rhashtable_compare(&arg, rht_obj(ht, head)))))
+ goto out;
+ }
+
+skip_lookup:
+ 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);
+ if (rht_grow_above_75(ht, tbl))
+ schedule_work(&ht->run_work);
+
+out:
+ spin_unlock_bh(lock);
+ rcu_read_unlock();
+
+ return err;
+}
+
+/**
+ * rhashtable_insert_fast - insert object into hash table
+ * @ht: hash table
+ * @obj: pointer to hash head inside object
+ * @params: hash table parameters
+ *
+ * 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().
+ */
+static inline int rhashtable_insert_fast(
+ struct rhashtable *ht, struct rhash_head *obj,
+ const struct rhashtable_params params)
+{
+ return __rhashtable_insert_fast(ht, NULL, obj, params);
+}
+
+/**
+ * rhashtable_lookup_insert_fast - lookup and insert object into hash table
+ * @ht: hash table
+ * @obj: pointer to hash head inside object
+ * @params: hash table parameters
+ *
+ * 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().
+ */
+static inline int rhashtable_lookup_insert_fast(
+ struct rhashtable *ht, struct rhash_head *obj,
+ const struct rhashtable_params params)
+{
+ const char *key = rht_obj(ht, obj);
+
+ BUG_ON(ht->p.obj_hashfn);
+
+ return __rhashtable_insert_fast(ht, key + ht->p.key_offset, obj,
+ params);
+}
+
+/**
+ * rhashtable_lookup_insert_key - search and insert object to hash table
+ * with explicit key
+ * @ht: hash table
+ * @key: key
+ * @obj: pointer to hash head inside object
+ * @params: hash table parameters
+ *
+ * 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().
+ *
+ * Returns zero on success.
+ */
+static inline int rhashtable_lookup_insert_key(
+ struct rhashtable *ht, const void *key, struct rhash_head *obj,
+ const struct rhashtable_params params)
+{
+ BUG_ON(!ht->p.obj_hashfn || !key);
+
+ return __rhashtable_insert_fast(ht, key, obj, params);
+}
+
+static inline int __rhashtable_remove_fast(
+ struct rhashtable *ht, struct bucket_table *tbl,
+ struct rhash_head *obj, const struct rhashtable_params params)
+{
+ struct rhash_head __rcu **pprev;
+ struct rhash_head *he;
+ spinlock_t * lock;
+ unsigned hash;
+ int err = -ENOENT;
+
+ hash = rht_head_hashfn(ht, tbl, obj, params);
+ 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);
+ err = 0;
+ break;
+ }
+
+ spin_unlock_bh(lock);
+
+ return err;
+}
+
+/**
+ * rhashtable_remove_fast - remove object from hash table
+ * @ht: hash table
+ * @obj: pointer to hash head inside object
+ * @params: hash table parameters
+ *
+ * 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.
+ *
+ * Returns zero on success, -ENOENT if the entry could not be found.
+ */
+static inline int rhashtable_remove_fast(
+ struct rhashtable *ht, struct rhash_head *obj,
+ const struct rhashtable_params params)
+{
+ struct bucket_table *tbl;
+ int err;
+
+ 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 ((err = __rhashtable_remove_fast(ht, tbl, obj, params)) &&
+ (tbl = rht_dereference_rcu(tbl->future_tbl, ht)))
+ ;
+
+ if (err)
+ goto out;
+
+ atomic_dec(&ht->nelems);
+ if (rht_shrink_below_30(ht, tbl))
+ schedule_work(&ht->run_work);
+
+out:
+ rcu_read_unlock();
+
+ return err;
+}
+
#endif /* _LINUX_RHASHTABLE_H */
/*
* 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>
*
- * Based on the following paper:
- * 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
#define HASH_MIN_SIZE 4U
#define BUCKET_LOCKS_PER_CPU 128UL
-/* Base bits plus 1 bit for nulls marker */
-#define HASH_RESERVED_SPACE (RHT_BASE_BITS + 1)
-
-/* The bucket lock is selected based on the hash and protects mutations
- * on a group of hash buckets.
- *
- * A maximum of tbl->size/2 bucket locks is allocated. This ensures that
- * a single lock always covers both buckets which may both contains
- * entries which link to the same bucket of the old table during resizing.
- * This allows to simplify the locking as locking the bucket in both
- * tables during resize always guarantee protection.
- *
- * IMPORTANT: When holding the bucket lock of both the old and new table
- * during expansions and shrinking, the old bucket lock must always be
- * acquired first.
- */
-static spinlock_t *bucket_lock(const struct bucket_table *tbl, u32 hash)
-{
- return &tbl->locks[hash & tbl->locks_mask];
-}
-
-static void *rht_obj(const struct rhashtable *ht, const struct rhash_head *he)
-{
- return (void *) he - ht->p.head_offset;
-}
-
-static u32 rht_bucket_index(const struct bucket_table *tbl, u32 hash)
-{
- return (hash >> HASH_RESERVED_SPACE) & (tbl->size - 1);
-}
-
-static u32 key_hashfn(struct rhashtable *ht, const struct bucket_table *tbl,
- const void *key)
-{
- return rht_bucket_index(tbl, ht->p.hashfn(key, ht->p.key_len,
- tbl->hash_rnd));
-}
-
static u32 head_hashfn(struct rhashtable *ht,
const struct bucket_table *tbl,
const struct rhash_head *he)
{
- const char *ptr = rht_obj(ht, he);
-
- return likely(ht->p.key_len) ?
- key_hashfn(ht, tbl, ptr + ht->p.key_offset) :
- rht_bucket_index(tbl, ht->p.obj_hashfn(ptr, tbl->hash_rnd));
+ return rht_head_hashfn(ht, tbl, he, ht->p);
}
#ifdef CONFIG_PROVE_LOCKING
int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash)
{
- spinlock_t *lock = bucket_lock(tbl, hash);
+ spinlock_t *lock = rht_bucket_lock(tbl, hash);
return (debug_locks) ? lockdep_is_held(lock) : 1;
}
return tbl;
}
-/**
- * rht_grow_above_75 - returns true if nelems > 0.75 * table-size
- * @ht: hash table
- * @tbl: current table
- */
-static bool rht_grow_above_75(const struct rhashtable *ht,
- const struct bucket_table *tbl)
-{
- /* Expand table when exceeding 75% load */
- return atomic_read(&ht->nelems) > (tbl->size / 4 * 3) &&
- (!ht->p.max_size || tbl->size < ht->p.max_size);
-}
-
-/**
- * rht_shrink_below_30 - returns true if nelems < 0.3 * table-size
- * @ht: hash table
- * @tbl: current table
- */
-static bool rht_shrink_below_30(const struct rhashtable *ht,
- const struct bucket_table *tbl)
-{
- /* Shrink table beneath 30% load */
- return atomic_read(&ht->nelems) < (tbl->size * 3 / 10) &&
- tbl->size > ht->p.min_size;
-}
-
static int rhashtable_rehash_one(struct rhashtable *ht, unsigned old_hash)
{
struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
new_hash = head_hashfn(ht, new_tbl, entry);
- new_bucket_lock = bucket_lock(new_tbl, new_hash);
+ 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],
struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
spinlock_t *old_bucket_lock;
- old_bucket_lock = bucket_lock(old_tbl, old_hash);
+ old_bucket_lock = rht_bucket_lock(old_tbl, old_hash);
spin_lock_bh(old_bucket_lock);
while (!rhashtable_rehash_one(ht, old_hash))
mutex_unlock(&ht->mutex);
}
+int rhashtable_insert_slow(struct rhashtable *ht, const void *key,
+ struct rhash_head *obj,
+ struct bucket_table *tbl)
+{
+ struct rhash_head *head;
+ unsigned hash;
+ int err = -EEXIST;
+
+ hash = head_hashfn(ht, tbl, obj);
+ spin_lock_nested(rht_bucket_lock(tbl, hash), SINGLE_DEPTH_NESTING);
+
+ if (key && rhashtable_lookup_fast(ht, key, ht->p))
+ 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));
+
+ return err;
+}
+EXPORT_SYMBOL_GPL(rhashtable_insert_slow);
+
static bool __rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj,
bool (*compare)(void *, void *), void *arg)
{
old_tbl = rht_dereference_rcu(ht->tbl, ht);
hash = head_hashfn(ht, old_tbl, obj);
- old_lock = bucket_lock(old_tbl, hash);
+ old_lock = rht_bucket_lock(old_tbl, hash);
spin_lock_bh(old_lock);
tbl = rht_dereference_rcu(old_tbl->future_tbl, ht) ?: old_tbl;
if (tbl != old_tbl) {
hash = head_hashfn(ht, tbl, obj);
- spin_lock_nested(bucket_lock(tbl, hash), SINGLE_DEPTH_NESTING);
+ spin_lock_nested(rht_bucket_lock(tbl, hash),
+ SINGLE_DEPTH_NESTING);
}
if (compare &&
exit:
if (tbl != old_tbl)
- spin_unlock(bucket_lock(tbl, hash));
+ spin_unlock(rht_bucket_lock(tbl, hash));
spin_unlock_bh(old_lock);
bool ret = false;
hash = head_hashfn(ht, tbl, obj);
- lock = bucket_lock(tbl, hash);
+ lock = rht_bucket_lock(tbl, hash);
spin_lock_bh(lock);
}
EXPORT_SYMBOL_GPL(rhashtable_remove);
-struct rhashtable_compare_arg {
- struct rhashtable *ht;
- const void *key;
-};
-
-static bool rhashtable_compare(void *ptr, void *arg)
-{
- struct rhashtable_compare_arg *x = arg;
- struct rhashtable *ht = x->ht;
-
- return !memcmp(ptr + ht->p.key_offset, x->key, ht->p.key_len);
-}
-
/**
* rhashtable_lookup - lookup key in hash table
* @ht: hash table
*/
void *rhashtable_lookup(struct rhashtable *ht, const void *key)
{
- struct rhashtable_compare_arg arg = {
- .ht = ht,
- .key = key,
- };
-
- BUG_ON(!ht->p.key_len);
-
- return rhashtable_lookup_compare(ht, key, &rhashtable_compare, &arg);
+ return rhashtable_lookup_fast(ht, key, ht->p);
}
EXPORT_SYMBOL_GPL(rhashtable_lookup);
* 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)
+ bool (*compare)(void *, void *),
+ void *arg)
{
const struct bucket_table *tbl;
struct rhash_head *he;
tbl = rht_dereference_rcu(ht->tbl, ht);
restart:
- hash = key_hashfn(ht, tbl, key);
+ hash = rht_key_hashfn(ht, tbl, key, ht->p);
rht_for_each_rcu(he, tbl, hash) {
if (!compare(rht_obj(ht, he), arg))
continue;
*/
bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj)
{
- struct rhashtable_compare_arg arg = {
- .ht = ht,
- .key = rht_obj(ht, obj) + ht->p.key_offset,
- };
-
- BUG_ON(!ht->p.key_len);
-
- return rhashtable_lookup_compare_insert(ht, obj, &rhashtable_compare,
- &arg);
+ return rhashtable_lookup_insert_fast(ht, obj, ht->p);
}
EXPORT_SYMBOL_GPL(rhashtable_lookup_insert);
size = HASH_DEFAULT_SIZE;
- if ((params->key_len && !params->hashfn) ||
- (!params->key_len && !params->obj_hashfn))
+ if ((!(params->key_len && params->hashfn) && !params->obj_hashfn) ||
+ (params->obj_hashfn && !params->obj_cmpfn))
return -EINVAL;
if (params->nulls_base && params->nulls_base < (1U << RHT_BASE_SHIFT))
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