/*
* Resizable, Scalable, Concurrent Hash Table
*
- * Copyright (c) 2014 Thomas Graf <tgraf@suug.ch>
+ * 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 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
#define _LINUX_RHASHTABLE_H
#include <linux/compiler.h>
+#include <linux/errno.h>
+#include <linux/jhash.h>
#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 bucket_table - Table of hash buckets
* @size: Number of hash buckets
+ * @rehash: Current bucket being rehashed
+ * @hash_rnd: Random seed to fold into hash
* @locks_mask: Mask to apply before accessing locks[]
* @locks: Array of spinlocks protecting individual buckets
+ * @walkers: List of active walkers
+ * @rcu: RCU structure for freeing the table
+ * @future_tbl: Table under construction during rehashing
* @buckets: size * hash buckets
*/
struct bucket_table {
- size_t size;
+ unsigned int size;
+ unsigned int rehash;
+ u32 hash_rnd;
unsigned int locks_mask;
spinlock_t *locks;
+ struct list_head walkers;
+ struct rcu_head rcu;
+
+ struct bucket_table __rcu *future_tbl;
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 u32 (*rht_obj_hashfn_t)(const void *data, u32 len, u32 seed);
+typedef int (*rht_obj_cmpfn_t)(struct rhashtable_compare_arg *arg,
+ const void *obj);
struct rhashtable;
* @key_len: Length of key
* @key_offset: Offset of key in struct to be hashed
* @head_offset: Offset of rhash_head in struct to be hashed
- * @hash_rnd: Seed to use while hashing
- * @max_shift: Maximum number of shifts while expanding
- * @min_shift: Minimum number of shifts while shrinking
+ * @max_size: Maximum size while expanding
+ * @min_size: Minimum size while shrinking
* @nulls_base: Base value to generate nulls marker
+ * @insecure_elasticity: Set to true to disable chain length checks
+ * @automatic_shrinking: Enable automatic shrinking of tables
* @locks_mul: Number of bucket locks to allocate per cpu (default: 128)
- * @hashfn: Function to hash key
+ * @hashfn: Hash function (default: jhash2 if !(key_len % 4), or jhash)
* @obj_hashfn: Function to hash object
+ * @obj_cmpfn: Function to compare key with object
*/
struct rhashtable_params {
size_t nelem_hint;
size_t key_len;
size_t key_offset;
size_t head_offset;
- u32 hash_rnd;
- size_t max_shift;
- size_t min_shift;
+ unsigned int max_size;
+ unsigned int min_size;
u32 nulls_base;
+ bool insecure_elasticity;
+ bool automatic_shrinking;
size_t locks_mul;
rht_hashfn_t hashfn;
rht_obj_hashfn_t obj_hashfn;
+ rht_obj_cmpfn_t obj_cmpfn;
};
/**
* struct rhashtable - Hash table handle
* @tbl: Bucket table
- * @future_tbl: Table under construction during expansion/shrinking
* @nelems: Number of elements in table
- * @shift: Current size (1 << shift)
+ * @key_len: Key length for hashfn
+ * @elasticity: Maximum chain length before rehash
* @p: Configuration parameters
* @run_work: Deferred worker to expand/shrink asynchronously
* @mutex: Mutex to protect current/future table swapping
- * @walkers: List of active walkers
- * @being_destroyed: True if table is set up for destruction
+ * @lock: Spin lock to protect walker list
*/
struct rhashtable {
struct bucket_table __rcu *tbl;
- struct bucket_table __rcu *future_tbl;
atomic_t nelems;
- atomic_t shift;
+ unsigned int key_len;
+ unsigned int elasticity;
struct rhashtable_params p;
struct work_struct run_work;
struct mutex mutex;
- struct list_head walkers;
- bool being_destroyed;
+ spinlock_t lock;
};
/**
* struct rhashtable_walker - Hash table walker
* @list: List entry on list of walkers
- * @resize: Resize event occured
+ * @tbl: The table that we were walking over
*/
struct rhashtable_walker {
struct list_head list;
- bool resize;
+ struct bucket_table *tbl;
};
/**
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)
+{
+ unsigned int hash;
+
+ /* params must be equal to ht->p if it isn't constant. */
+ if (!__builtin_constant_p(params.key_len))
+ hash = ht->p.hashfn(key, ht->key_len, tbl->hash_rnd);
+ else if (params.key_len) {
+ unsigned int key_len = params.key_len;
+
+ if (params.hashfn)
+ hash = params.hashfn(key, key_len, tbl->hash_rnd);
+ else if (key_len & (sizeof(u32) - 1))
+ hash = jhash(key, key_len, tbl->hash_rnd);
+ else
+ hash = jhash2(key, key_len / sizeof(u32),
+ tbl->hash_rnd);
+ } else {
+ unsigned int key_len = ht->p.key_len;
+
+ if (params.hashfn)
+ hash = params.hashfn(key, key_len, tbl->hash_rnd);
+ else
+ hash = jhash(key, key_len, tbl->hash_rnd);
+ }
+
+ return rht_bucket_index(tbl, hash);
+}
+
+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, params.key_len ?:
+ ht->p.key_len,
+ 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;
+}
+
+/**
+ * rht_grow_above_100 - returns true if nelems > table-size
+ * @ht: hash table
+ * @tbl: current table
+ */
+static inline bool rht_grow_above_100(const struct rhashtable *ht,
+ const struct bucket_table *tbl)
+{
+ return atomic_read(&ht->nelems) > tbl->size &&
+ (!ht->p.max_size || tbl->size < ht->p.max_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);
}
#endif /* CONFIG_PROVE_LOCKING */
-int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params);
-
-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);
+int rhashtable_init(struct rhashtable *ht,
+ const struct rhashtable_params *params);
-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_insert_slow(struct rhashtable *ht, const void *key,
+ struct rhash_head *obj,
+ struct bucket_table *old_tbl);
+int rhashtable_insert_rehash(struct rhashtable *ht);
int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter);
void rhashtable_walk_exit(struct rhashtable_iter *iter);
void *rhashtable_walk_next(struct rhashtable_iter *iter);
void rhashtable_walk_stop(struct rhashtable_iter *iter) __releases(RCU);
+void rhashtable_free_and_destroy(struct rhashtable *ht,
+ void (*free_fn)(void *ptr, void *arg),
+ void *arg);
void rhashtable_destroy(struct rhashtable *ht);
#define rht_dereference(p, ht) \
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 int 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;
+}
+
+/* Internal function, please use rhashtable_insert_fast() instead */
+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,
+ };
+ struct bucket_table *tbl, *new_tbl;
+ struct rhash_head *head;
+ spinlock_t *lock;
+ unsigned int elasticity;
+ unsigned int hash;
+ int err;
+
+restart:
+ rcu_read_lock();
+
+ tbl = rht_dereference_rcu(ht->tbl, ht);
+
+ /* All insertions must grab the oldest table containing
+ * the hashed bucket that is yet to be rehashed.
+ */
+ for (;;) {
+ hash = rht_head_hashfn(ht, tbl, obj, params);
+ lock = rht_bucket_lock(tbl, hash);
+ spin_lock_bh(lock);
+
+ if (tbl->rehash <= hash)
+ break;
+
+ spin_unlock_bh(lock);
+ tbl = rht_dereference_rcu(tbl->future_tbl, ht);
+ }
+
+ new_tbl = rht_dereference_rcu(tbl->future_tbl, ht);
+ if (unlikely(new_tbl)) {
+ err = rhashtable_insert_slow(ht, key, obj, new_tbl);
+ if (err == -EAGAIN)
+ goto slow_path;
+ goto out;
+ }
+
+ if (unlikely(rht_grow_above_100(ht, tbl))) {
+slow_path:
+ spin_unlock_bh(lock);
+ err = rhashtable_insert_rehash(ht);
+ rcu_read_unlock();
+ if (err)
+ return err;
+
+ goto restart;
+ }
+
+ err = -EEXIST;
+ elasticity = ht->elasticity;
+ rht_for_each(head, tbl, hash) {
+ if (key &&
+ unlikely(!(params.obj_cmpfn ?
+ params.obj_cmpfn(&arg, rht_obj(ht, head)) :
+ rhashtable_compare(&arg, rht_obj(ht, head)))))
+ goto out;
+ if (!--elasticity)
+ goto slow_path;
+ }
+
+ 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);
+}
+
+/* Internal function, please use rhashtable_remove_fast() instead */
+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 int 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 (unlikely(ht->p.automatic_shrinking &&
+ rht_shrink_below_30(ht, tbl)))
+ schedule_work(&ht->run_work);
+
+out:
+ rcu_read_unlock();
+
+ return err;
+}
+
#endif /* _LINUX_RHASHTABLE_H */
projects / linux-2.6-block.git / blobdiff