/* SPDX-License-Identifier: GPL-2.0 */ /* * Resizable, Scalable, Concurrent Hash Table * * Copyright (c) 2015-2016 Herbert Xu <[email protected]> * Copyright (c) 2014-2015 Thomas Graf <[email protected]> * Copyright (c) 2008-2014 Patrick McHardy <[email protected]> * * 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. */ #ifndef _LINUX_RHASHTABLE_H #define _LINUX_RHASHTABLE_H #include <linux/err.h> #include <linux/errno.h> #include <linux/jhash.h> #include <linux/list_nulls.h> #include <linux/workqueue.h> #include <linux/rculist.h> #include <linux/bit_spinlock.h> #include <linux/rhashtable-types.h> /* * Objects in an rhashtable have an embedded struct rhash_head * which is linked into as hash chain from the hash table - or one * of two or more hash tables when the rhashtable is being resized. * The end of the chain is marked with a special nulls marks which has * the least significant bit set but otherwise stores the address of * the hash bucket. This allows us to be sure we've found the end * of the right list. * The value stored in the hash bucket has BIT(0) used as a lock bit. * This bit must be atomically set before any changes are made to * the chain. To avoid dereferencing this pointer without clearing * the bit first, we use an opaque 'struct rhash_lock_head *' for the * pointer stored in the bucket. This struct needs to be defined so * that rcu_dereference() works on it, but it has no content so a * cast is needed for it to be useful. This ensures it isn't * used by mistake with clearing the lock bit first. */ struct rhash_lock_head { … }; /* Maximum chain length before rehash * * 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. */ #define RHT_ELASTICITY … /** * struct bucket_table - Table of hash buckets * @size: Number of hash buckets * @nest: Number of bits of first-level nested table. * @rehash: Current bucket being rehashed * @hash_rnd: Random seed to fold into hash * @walkers: List of active walkers * @rcu: RCU structure for freeing the table * @future_tbl: Table under construction during rehashing * @ntbl: Nested table used when out of memory. * @buckets: size * hash buckets */ struct bucket_table { … }; /* * NULLS_MARKER() expects a hash value with the low * bits mostly likely to be significant, and it discards * the msb. * We give it an address, in which the bottom bit is * always 0, and the msb might be significant. * So we shift the address down one bit to align with * expectations and avoid losing a significant bit. * * We never store the NULLS_MARKER in the hash table * itself as we need the lsb for locking. * Instead we store a NULL */ #define RHT_NULLS_MARKER(ptr) … #define INIT_RHT_NULLS_HEAD(ptr) … static inline bool rht_is_a_nulls(const struct rhash_head *ptr) { … } static inline void *rht_obj(const struct rhashtable *ht, const struct rhash_head *he) { … } static inline unsigned int rht_bucket_index(const struct bucket_table *tbl, unsigned int hash) { … } static inline unsigned int rht_key_get_hash(struct rhashtable *ht, const void *key, const struct rhashtable_params params, unsigned int hash_rnd) { … } static inline unsigned int rht_key_hashfn( struct rhashtable *ht, const struct bucket_table *tbl, const void *key, const struct rhashtable_params params) { … } 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) { … } /** * 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) { … } /** * 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) { … } /** * 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) { … } /** * rht_grow_above_max - returns true if table is above maximum * @ht: hash table * @tbl: current table */ static inline bool rht_grow_above_max(const struct rhashtable *ht, const struct bucket_table *tbl) { … } #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); #else static inline int lockdep_rht_mutex_is_held(struct rhashtable *ht) { return 1; } static inline int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash) { return 1; } #endif /* CONFIG_PROVE_LOCKING */ void *rhashtable_insert_slow(struct rhashtable *ht, const void *key, struct rhash_head *obj); void rhashtable_walk_enter(struct rhashtable *ht, struct rhashtable_iter *iter); void rhashtable_walk_exit(struct rhashtable_iter *iter); int rhashtable_walk_start_check(struct rhashtable_iter *iter) __acquires(…); static inline void rhashtable_walk_start(struct rhashtable_iter *iter) { … } void *rhashtable_walk_next(struct rhashtable_iter *iter); void *rhashtable_walk_peek(struct rhashtable_iter *iter); void rhashtable_walk_stop(struct rhashtable_iter *iter) __releases(…); void rhashtable_free_and_destroy(struct rhashtable *ht, void (*free_fn)(void *ptr, void *arg), void *arg); void rhashtable_destroy(struct rhashtable *ht); struct rhash_lock_head __rcu **rht_bucket_nested( const struct bucket_table *tbl, unsigned int hash); struct rhash_lock_head __rcu **__rht_bucket_nested( const struct bucket_table *tbl, unsigned int hash); struct rhash_lock_head __rcu **rht_bucket_nested_insert( struct rhashtable *ht, struct bucket_table *tbl, unsigned int hash); #define rht_dereference(p, ht) … #define rht_dereference_rcu(p, ht) … #define rht_dereference_bucket(p, tbl, hash) … #define rht_dereference_bucket_rcu(p, tbl, hash) … #define rht_entry(tpos, pos, member) … static inline struct rhash_lock_head __rcu *const *rht_bucket( const struct bucket_table *tbl, unsigned int hash) { … } static inline struct rhash_lock_head __rcu **rht_bucket_var( struct bucket_table *tbl, unsigned int hash) { … } static inline struct rhash_lock_head __rcu **rht_bucket_insert( struct rhashtable *ht, struct bucket_table *tbl, unsigned int hash) { … } /* * We lock a bucket by setting BIT(0) in the pointer - this is always * zero in real pointers. The NULLS mark is never stored in the bucket, * rather we store NULL if the bucket is empty. * bit_spin_locks do not handle contention well, but the whole point * of the hashtable design is to achieve minimum per-bucket contention. * A nested hash table might not have a bucket pointer. In that case * we cannot get a lock. For remove and replace the bucket cannot be * interesting and doesn't need locking. * For insert we allocate the bucket if this is the last bucket_table, * and then take the lock. * Sometimes we unlock a bucket by writing a new pointer there. In that * case we don't need to unlock, but we do need to reset state such as * local_bh. For that we have rht_assign_unlock(). As rcu_assign_pointer() * provides the same release semantics that bit_spin_unlock() provides, * this is safe. * When we write to a bucket without unlocking, we use rht_assign_locked(). */ static inline unsigned long rht_lock(struct bucket_table *tbl, struct rhash_lock_head __rcu **bkt) { … } static inline unsigned long rht_lock_nested(struct bucket_table *tbl, struct rhash_lock_head __rcu **bucket, unsigned int subclass) { … } static inline void rht_unlock(struct bucket_table *tbl, struct rhash_lock_head __rcu **bkt, unsigned long flags) { … } static inline struct rhash_head *__rht_ptr( struct rhash_lock_head *p, struct rhash_lock_head __rcu *const *bkt) { … } /* * Where 'bkt' is a bucket and might be locked: * rht_ptr_rcu() dereferences that pointer and clears the lock bit. * rht_ptr() dereferences in a context where the bucket is locked. * rht_ptr_exclusive() dereferences in a context where exclusive * access is guaranteed, such as when destroying the table. */ static inline struct rhash_head *rht_ptr_rcu( struct rhash_lock_head __rcu *const *bkt) { … } static inline struct rhash_head *rht_ptr( struct rhash_lock_head __rcu *const *bkt, struct bucket_table *tbl, unsigned int hash) { … } static inline struct rhash_head *rht_ptr_exclusive( struct rhash_lock_head __rcu *const *bkt) { … } static inline void rht_assign_locked(struct rhash_lock_head __rcu **bkt, struct rhash_head *obj) { … } static inline void rht_assign_unlock(struct bucket_table *tbl, struct rhash_lock_head __rcu **bkt, struct rhash_head *obj, unsigned long flags) { … } /** * rht_for_each_from - iterate over hash chain from given head * @pos: the &struct rhash_head to use as a loop cursor. * @head: the &struct rhash_head to start from * @tbl: the &struct bucket_table * @hash: the hash value / bucket index */ #define rht_for_each_from(pos, head, tbl, hash) … /** * rht_for_each - iterate over hash chain * @pos: the &struct rhash_head to use as a loop cursor. * @tbl: the &struct bucket_table * @hash: the hash value / bucket index */ #define rht_for_each(pos, tbl, hash) … /** * rht_for_each_entry_from - iterate over hash chain from given head * @tpos: the type * to use as a loop cursor. * @pos: the &struct rhash_head to use as a loop cursor. * @head: the &struct rhash_head to start from * @tbl: the &struct bucket_table * @hash: the hash value / bucket index * @member: name of the &struct rhash_head within the hashable struct. */ #define rht_for_each_entry_from(tpos, pos, head, tbl, hash, member) … /** * rht_for_each_entry - iterate over hash chain of given type * @tpos: the type * to use as a loop cursor. * @pos: the &struct rhash_head to use as a loop cursor. * @tbl: the &struct bucket_table * @hash: the hash value / bucket index * @member: name of the &struct rhash_head within the hashable struct. */ #define rht_for_each_entry(tpos, pos, tbl, hash, member) … /** * rht_for_each_entry_safe - safely iterate over hash chain of given type * @tpos: the type * to use as a loop cursor. * @pos: the &struct rhash_head to use as a loop cursor. * @next: the &struct rhash_head to use as next in loop cursor. * @tbl: the &struct bucket_table * @hash: the hash value / bucket index * @member: name of the &struct rhash_head within the hashable struct. * * This hash chain list-traversal primitive allows for the looped code to * remove the loop cursor from the list. */ #define rht_for_each_entry_safe(tpos, pos, next, tbl, hash, member) … /** * rht_for_each_rcu_from - iterate over rcu hash chain from given head * @pos: the &struct rhash_head to use as a loop cursor. * @head: the &struct rhash_head to start from * @tbl: the &struct bucket_table * @hash: the hash value / bucket index * * This hash chain list-traversal primitive may safely run concurrently with * the _rcu mutation primitives such as rhashtable_insert() as long as the * traversal is guarded by rcu_read_lock(). */ #define rht_for_each_rcu_from(pos, head, tbl, hash) … /** * rht_for_each_rcu - iterate over rcu hash chain * @pos: the &struct rhash_head to use as a loop cursor. * @tbl: the &struct bucket_table * @hash: the hash value / bucket index * * This hash chain list-traversal primitive may safely run concurrently with * the _rcu mutation primitives such as rhashtable_insert() as long as the * traversal is guarded by rcu_read_lock(). */ #define rht_for_each_rcu(pos, tbl, hash) … /** * rht_for_each_entry_rcu_from - iterated over rcu hash chain from given head * @tpos: the type * to use as a loop cursor. * @pos: the &struct rhash_head to use as a loop cursor. * @head: the &struct rhash_head to start from * @tbl: the &struct bucket_table * @hash: the hash value / bucket index * @member: name of the &struct rhash_head within the hashable struct. * * This hash chain list-traversal primitive may safely run concurrently with * the _rcu mutation primitives such as rhashtable_insert() as long as the * traversal is guarded by rcu_read_lock(). */ #define rht_for_each_entry_rcu_from(tpos, pos, head, tbl, hash, member) … /** * rht_for_each_entry_rcu - iterate over rcu hash chain of given type * @tpos: the type * to use as a loop cursor. * @pos: the &struct rhash_head to use as a loop cursor. * @tbl: the &struct bucket_table * @hash: the hash value / bucket index * @member: name of the &struct rhash_head within the hashable struct. * * This hash chain list-traversal primitive may safely run concurrently with * the _rcu mutation primitives such as rhashtable_insert() as long as the * traversal is guarded by rcu_read_lock(). */ #define rht_for_each_entry_rcu(tpos, pos, tbl, hash, member) … /** * rhl_for_each_rcu - iterate over rcu hash table list * @pos: the &struct rlist_head to use as a loop cursor. * @list: the head of the list * * This hash chain list-traversal primitive should be used on the * list returned by rhltable_lookup. */ #define rhl_for_each_rcu(pos, list) … /** * rhl_for_each_entry_rcu - iterate over rcu hash table list of given type * @tpos: the type * to use as a loop cursor. * @pos: the &struct rlist_head to use as a loop cursor. * @list: the head of the list * @member: name of the &struct rlist_head within the hashable struct. * * This hash chain list-traversal primitive should be used on the * list returned by rhltable_lookup. */ #define rhl_for_each_entry_rcu(tpos, pos, list, member) … static inline int rhashtable_compare(struct rhashtable_compare_arg *arg, const void *obj) { … } /* Internal function, do not use. */ static inline struct rhash_head *__rhashtable_lookup( struct rhashtable *ht, const void *key, const struct rhashtable_params params) { … } /** * rhashtable_lookup - search hash table * @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 an entry with an identical key. The first matching entry is returned. * * This must only be called under the RCU read lock. * * Returns the first entry on which the compare function returned true. */ static inline void *rhashtable_lookup( struct rhashtable *ht, const void *key, const struct rhashtable_params params) { … } /** * rhashtable_lookup_fast - search hash table, without RCU read lock * @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 an entry with an identical key. The first matching entry is returned. * * Only use this function when you have other mechanisms guaranteeing * that the object won't go away after the RCU read lock is released. * * 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) { … } /** * rhltable_lookup - search hash list table * @hlt: 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 an entry with an identical key. All matching entries are returned * in a list. * * This must only be called under the RCU read lock. * * Returns the list of entries that match the given key. */ static inline struct rhlist_head *rhltable_lookup( struct rhltable *hlt, const void *key, const struct rhashtable_params params) { … } /* Internal function, please use rhashtable_insert_fast() instead. This * function returns the existing element already in hashes if there is a clash, * otherwise it returns an error via ERR_PTR(). */ static inline void *__rhashtable_insert_fast( struct rhashtable *ht, const void *key, struct rhash_head *obj, const struct rhashtable_params params, bool rhlist) { … } /** * rhashtable_insert_fast - insert object into hash table * @ht: hash table * @obj: pointer to hash head inside object * @params: hash table parameters * * Will take the per bucket bitlock to protect against mutual mutations * on the same bucket. Multiple insertions may occur in parallel unless * they map to the same bucket. * * It is safe to call this function from atomic context. * * Will trigger an automatic deferred table resizing if residency in the * table grows beyond 70%. */ static inline int rhashtable_insert_fast( struct rhashtable *ht, struct rhash_head *obj, const struct rhashtable_params params) { … } /** * rhltable_insert_key - insert object into hash list table * @hlt: hash list table * @key: the pointer to the key * @list: pointer to hash list head inside object * @params: hash table parameters * * Will take the per bucket bitlock to protect against mutual mutations * on the same bucket. Multiple insertions may occur in parallel unless * they map to the same bucket. * * It is safe to call this function from atomic context. * * Will trigger an automatic deferred table resizing if residency in the * table grows beyond 70%. */ static inline int rhltable_insert_key( struct rhltable *hlt, const void *key, struct rhlist_head *list, const struct rhashtable_params params) { … } /** * rhltable_insert - insert object into hash list table * @hlt: hash list table * @list: pointer to hash list head inside object * @params: hash table parameters * * Will take the per bucket bitlock to protect against mutual mutations * on the same bucket. Multiple insertions may occur in parallel unless * they map to the same bucket. * * It is safe to call this function from atomic context. * * Will trigger an automatic deferred table resizing if residency in the * table grows beyond 70%. */ static inline int rhltable_insert( struct rhltable *hlt, struct rhlist_head *list, const struct rhashtable_params 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 * * 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 residency in the * table grows beyond 70%. */ static inline int rhashtable_lookup_insert_fast( struct rhashtable *ht, struct rhash_head *obj, const struct rhashtable_params params) { … } /** * rhashtable_lookup_get_insert_fast - lookup and insert object into hash table * @ht: hash table * @obj: pointer to hash head inside object * @params: hash table parameters * * Just like rhashtable_lookup_insert_fast(), but this function returns the * object if it exists, NULL if it did not and the insertion was successful, * and an ERR_PTR otherwise. */ static inline void *rhashtable_lookup_get_insert_fast( struct rhashtable *ht, struct rhash_head *obj, const struct rhashtable_params 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 * * Lookups may occur in parallel with hashtable mutations and resizing. * * Will trigger an automatic deferred table resizing if residency in the * table grows beyond 70%. * * 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) { … } /** * rhashtable_lookup_get_insert_key - lookup and insert object into hash table * @ht: hash table * @key: key * @obj: pointer to hash head inside object * @params: hash table parameters * * Just like rhashtable_lookup_insert_key(), but this function returns the * object if it exists, NULL if it does not and the insertion was successful, * and an ERR_PTR otherwise. */ static inline void *rhashtable_lookup_get_insert_key( struct rhashtable *ht, const void *key, struct rhash_head *obj, const struct rhashtable_params params) { … } /* Internal function, please use rhashtable_remove_fast() instead */ static inline int __rhashtable_remove_fast_one( struct rhashtable *ht, struct bucket_table *tbl, struct rhash_head *obj, const struct rhashtable_params params, bool rhlist) { … } /* Internal function, please use rhashtable_remove_fast() instead */ static inline int __rhashtable_remove_fast( struct rhashtable *ht, struct rhash_head *obj, const struct rhashtable_params params, bool rhlist) { … } /** * 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 if permitted when residency drops * below 30%. * * 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) { … } /** * rhltable_remove - remove object from hash list table * @hlt: hash list table * @list: pointer to hash list 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 * considerably slower if the hash table is not correctly sized. * * Will automatically shrink the table if permitted when residency drops * below 30% * * Returns zero on success, -ENOENT if the entry could not be found. */ static inline int rhltable_remove( struct rhltable *hlt, struct rhlist_head *list, const struct rhashtable_params params) { … } /* Internal function, please use rhashtable_replace_fast() instead */ static inline int __rhashtable_replace_fast( struct rhashtable *ht, struct bucket_table *tbl, struct rhash_head *obj_old, struct rhash_head *obj_new, const struct rhashtable_params params) { … } /** * rhashtable_replace_fast - replace an object in hash table * @ht: hash table * @obj_old: pointer to hash head inside object being replaced * @obj_new: pointer to hash head inside object which is new * @params: hash table parameters * * Replacing an object doesn't affect the number of elements in the hash table * or bucket, so we don't need to worry about shrinking or expanding the * table here. * * Returns zero on success, -ENOENT if the entry could not be found, * -EINVAL if hash is not the same for the old and new objects. */ static inline int rhashtable_replace_fast( struct rhashtable *ht, struct rhash_head *obj_old, struct rhash_head *obj_new, const struct rhashtable_params params) { … } /** * rhltable_walk_enter - Initialise an iterator * @hlt: 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 be called from any process context, including * non-preemptable context, but cannot be called from softirq or * hardirq context. * * You must call rhashtable_walk_exit after this function returns. */ static inline void rhltable_walk_enter(struct rhltable *hlt, struct rhashtable_iter *iter) { … } /** * rhltable_free_and_destroy - free elements and destroy hash list table * @hlt: the hash list table to destroy * @free_fn: callback to release resources of element * @arg: pointer passed to free_fn * * See documentation for rhashtable_free_and_destroy. */ static inline void rhltable_free_and_destroy(struct rhltable *hlt, void (*free_fn)(void *ptr, void *arg), void *arg) { … } static inline void rhltable_destroy(struct rhltable *hlt) { … } #endif /* _LINUX_RHASHTABLE_H */
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