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/* SPDX-License-Identifier: GPL-2.0 */ /* * Resizable, Scalable, Concurrent Hash Table * * Copyright (c) 2015-2016 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. */ #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 16u /** * 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 { unsigned int size; unsigned int nest; u32 hash_rnd; struct list_head walkers; struct rcu_head rcu; struct bucket_table __rcu *future_tbl; struct lockdep_map dep_map; struct rhash_lock_head __rcu *buckets[] ____cacheline_aligned_in_smp; }; /* * 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) \ ((void *)NULLS_MARKER(((unsigned long) (ptr)) >> 1)) #define INIT_RHT_NULLS_HEAD(ptr) \ ((ptr) = NULL) static inline bool rht_is_a_nulls(const struct rhash_head *ptr) { 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 & (tbl->size - 1); } static inline unsigned int rht_key_get_hash(struct rhashtable *ht, const void *key, const struct rhashtable_params params, unsigned int hash_rnd) { 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, hash_rnd); else if (params.key_len) { unsigned int key_len = params.key_len; if (params.hashfn) hash = params.hashfn(key, key_len, hash_rnd); else if (key_len & (sizeof(u32) - 1)) hash = jhash(key, key_len, hash_rnd); else hash = jhash2(key, key_len / sizeof(u32), hash_rnd); } else { unsigned int key_len = ht->p.key_len; if (params.hashfn) hash = params.hashfn(key, key_len, hash_rnd); else hash = jhash(key, key_len, hash_rnd); } return hash; } 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 = rht_key_get_hash(ht, key, params, 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); } /** * 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) { return atomic_read(&ht->nelems) >= ht->max_elems; } #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(RCU); static inline void rhashtable_walk_start(struct rhashtable_iter *iter) { (void)rhashtable_walk_start_check(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(RCU); 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) \ rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht)) #define rht_dereference_rcu(p, ht) \ rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht)) #define rht_dereference_bucket(p, tbl, hash) \ rcu_dereference_protected(p, lockdep_rht_bucket_is_held(tbl, hash)) #define rht_dereference_bucket_rcu(p, tbl, hash) \ rcu_dereference_check(p, lockdep_rht_bucket_is_held(tbl, hash)) #define rht_entry(tpos, pos, member) \ ({ tpos = container_of(pos, typeof(*tpos), member); 1; }) static inline struct rhash_lock_head __rcu *const *rht_bucket( const struct bucket_table *tbl, unsigned int hash) { return unlikely(tbl->nest) ? rht_bucket_nested(tbl, hash) : &tbl->buckets[hash]; } static inline struct rhash_lock_head __rcu **rht_bucket_var( struct bucket_table *tbl, unsigned int hash) { return unlikely(tbl->nest) ? __rht_bucket_nested(tbl, hash) : &tbl->buckets[hash]; } static inline struct rhash_lock_head __rcu **rht_bucket_insert( struct rhashtable *ht, struct bucket_table *tbl, unsigned int hash) { return unlikely(tbl->nest) ? rht_bucket_nested_insert(ht, tbl, hash) : &tbl->buckets[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) { unsigned long flags; local_irq_save(flags); bit_spin_lock(0, (unsigned long *)bkt); lock_map_acquire(&tbl->dep_map); return flags; } static inline unsigned long rht_lock_nested(struct bucket_table *tbl, struct rhash_lock_head __rcu **bucket, unsigned int subclass) { unsigned long flags; local_irq_save(flags); bit_spin_lock(0, (unsigned long *)bucket); lock_acquire_exclusive(&tbl->dep_map, subclass, 0, NULL, _THIS_IP_); return flags; } static inline void rht_unlock(struct bucket_table *tbl, struct rhash_lock_head __rcu **bkt, unsigned long flags) { lock_map_release(&tbl->dep_map); bit_spin_unlock(0, (unsigned long *)bkt); local_irq_restore(flags); } static inline struct rhash_head *__rht_ptr( struct rhash_lock_head *p, struct rhash_lock_head __rcu *const *bkt) { return (struct rhash_head *) ((unsigned long)p & ~BIT(0) ?: (unsigned long)RHT_NULLS_MARKER(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) { return __rht_ptr(rcu_dereference(*bkt), bkt); } static inline struct rhash_head *rht_ptr( struct rhash_lock_head __rcu *const *bkt, struct bucket_table *tbl, unsigned int hash) { return __rht_ptr(rht_dereference_bucket(*bkt, tbl, hash), bkt); } static inline struct rhash_head *rht_ptr_exclusive( struct rhash_lock_head __rcu *const *bkt) { return __rht_ptr(rcu_dereference_protected(*bkt, 1), bkt); } static inline void rht_assign_locked(struct rhash_lock_head __rcu **bkt, struct rhash_head *obj) { if (rht_is_a_nulls(obj)) obj = NULL; rcu_assign_pointer(*bkt, (void *)((unsigned long)obj | BIT(0))); } static inline void rht_assign_unlock(struct bucket_table *tbl, struct rhash_lock_head __rcu **bkt, struct rhash_head *obj, unsigned long flags) { if (rht_is_a_nulls(obj)) obj = NULL; lock_map_release(&tbl->dep_map); rcu_assign_pointer(*bkt, (void *)obj); preempt_enable(); __release(bitlock); local_irq_restore(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) \ for (pos = head; \ !rht_is_a_nulls(pos); \ pos = rht_dereference_bucket((pos)->next, 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_from(pos, rht_ptr(rht_bucket(tbl, hash), tbl, hash), \ 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) \ for (pos = head; \ (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \ pos = rht_dereference_bucket((pos)->next, tbl, hash)) /** * 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_from(tpos, pos, \ rht_ptr(rht_bucket(tbl, hash), tbl, hash), \ 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) \ for (pos = rht_ptr(rht_bucket(tbl, hash), tbl, hash), \ next = !rht_is_a_nulls(pos) ? \ rht_dereference_bucket(pos->next, tbl, hash) : NULL; \ (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \ pos = next, \ next = !rht_is_a_nulls(pos) ? \ rht_dereference_bucket(pos->next, tbl, hash) : NULL) /** * 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) \ for (({barrier(); }), \ pos = head; \ !rht_is_a_nulls(pos); \ pos = rcu_dereference_raw(pos->next)) /** * 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) \ for (({barrier(); }), \ pos = rht_ptr_rcu(rht_bucket(tbl, hash)); \ !rht_is_a_nulls(pos); \ pos = rcu_dereference_raw(pos->next)) /** * 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) \ for (({barrier(); }), \ pos = head; \ (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \ pos = rht_dereference_bucket_rcu(pos->next, tbl, hash)) /** * 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) \ rht_for_each_entry_rcu_from(tpos, pos, \ rht_ptr_rcu(rht_bucket(tbl, hash)), \ 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) \ for (pos = list; pos; pos = rcu_dereference_raw(pos->next)) /** * 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) \ for (pos = list; pos && rht_entry(tpos, pos, member); \ pos = rcu_dereference_raw(pos->next)) 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); } /* Internal function, do not use. */ static inline struct rhash_head *__rhashtable_lookup( struct rhashtable *ht, const void *key, const struct rhashtable_params params) { struct rhashtable_compare_arg arg = { .ht = ht, .key = key, }; struct rhash_lock_head __rcu *const *bkt; struct bucket_table *tbl; struct rhash_head *he; unsigned int hash; tbl = rht_dereference_rcu(ht->tbl, ht); restart: hash = rht_key_hashfn(ht, tbl, key, params); bkt = rht_bucket(tbl, hash); do { rht_for_each_rcu_from(he, rht_ptr_rcu(bkt), tbl, hash) { if (params.obj_cmpfn ? params.obj_cmpfn(&arg, rht_obj(ht, he)) : rhashtable_compare(&arg, rht_obj(ht, he))) continue; return he; } /* An object might have been moved to a different hash chain, * while we walk along it - better check and retry. */ } while (he != RHT_NULLS_MARKER(bkt)); /* Ensure we see any new tables. */ smp_rmb(); tbl = rht_dereference_rcu(tbl->future_tbl, ht); if (unlikely(tbl)) goto restart; return NULL; } /** * 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) { struct rhash_head *he = __rhashtable_lookup(ht, key, params); return he ? rht_obj(ht, he) : NULL; } /** * 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) { void *obj; rcu_read_lock(); obj = rhashtable_lookup(ht, key, params); rcu_read_unlock(); return obj; } /** * 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) { struct rhash_head *he = __rhashtable_lookup(&hlt->ht, key, params); return he ? container_of(he, struct rhlist_head, rhead) : NULL; } /* 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) { struct rhashtable_compare_arg arg = { .ht = ht, .key = key, }; struct rhash_lock_head __rcu **bkt; struct rhash_head __rcu **pprev; struct bucket_table *tbl; struct rhash_head *head; unsigned long flags; unsigned int hash; int elasticity; void *data; rcu_read_lock(); tbl = rht_dereference_rcu(ht->tbl, ht); hash = rht_head_hashfn(ht, tbl, obj, params); elasticity = RHT_ELASTICITY; bkt = rht_bucket_insert(ht, tbl, hash); data = ERR_PTR(-ENOMEM); if (!bkt) goto out; pprev = NULL; flags = rht_lock(tbl, bkt); if (unlikely(rcu_access_pointer(tbl->future_tbl))) { slow_path: rht_unlock(tbl, bkt, flags); rcu_read_unlock(); return rhashtable_insert_slow(ht, key, obj); } rht_for_each_from(head, rht_ptr(bkt, tbl, hash), tbl, hash) { struct rhlist_head *plist; struct rhlist_head *list; elasticity--; if (!key || (params.obj_cmpfn ? params.obj_cmpfn(&arg, rht_obj(ht, head)) : rhashtable_compare(&arg, rht_obj(ht, head)))) { pprev = &head->next; continue; } data = rht_obj(ht, head); if (!rhlist) goto out_unlock; list = container_of(obj, struct rhlist_head, rhead); plist = container_of(head, struct rhlist_head, rhead); RCU_INIT_POINTER(list->next, plist); head = rht_dereference_bucket(head->next, tbl, hash); RCU_INIT_POINTER(list->rhead.next, head); if (pprev) { rcu_assign_pointer(*pprev, obj); rht_unlock(tbl, bkt, flags); } else rht_assign_unlock(tbl, bkt, obj, flags); data = NULL; goto out; } if (elasticity <= 0) goto slow_path; data = ERR_PTR(-E2BIG); if (unlikely(rht_grow_above_max(ht, tbl))) goto out_unlock; if (unlikely(rht_grow_above_100(ht, tbl))) goto slow_path; /* Inserting at head of list makes unlocking free. */ head = rht_ptr(bkt, tbl, hash); RCU_INIT_POINTER(obj->next, head); if (rhlist) { struct rhlist_head *list; list = container_of(obj, struct rhlist_head, rhead); RCU_INIT_POINTER(list->next, NULL); } atomic_inc(&ht->nelems); rht_assign_unlock(tbl, bkt, obj, flags); if (rht_grow_above_75(ht, tbl)) schedule_work(&ht->run_work); data = NULL; out: rcu_read_unlock(); return data; out_unlock: rht_unlock(tbl, bkt, flags); goto out; } /** * 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) { void *ret; ret = __rhashtable_insert_fast(ht, NULL, obj, params, false); if (IS_ERR(ret)) return PTR_ERR(ret); return ret == NULL ? 0 : -EEXIST; } /** * 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) { return PTR_ERR(__rhashtable_insert_fast(&hlt->ht, key, &list->rhead, params, true)); } /** * 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) { const char *key = rht_obj(&hlt->ht, &list->rhead); key += params.key_offset; return rhltable_insert_key(hlt, key, list, 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) { const char *key = rht_obj(ht, obj); void *ret; BUG_ON(ht->p.obj_hashfn); ret = __rhashtable_insert_fast(ht, key + ht->p.key_offset, obj, params, false); if (IS_ERR(ret)) return PTR_ERR(ret); return ret == NULL ? 0 : -EEXIST; } /** * 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) { 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, false); } /** * 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) { void *ret; BUG_ON(!ht->p.obj_hashfn || !key); ret = __rhashtable_insert_fast(ht, key, obj, params, false); if (IS_ERR(ret)) return PTR_ERR(ret); return ret == NULL ? 0 : -EEXIST; } /** * 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) { BUG_ON(!ht->p.obj_hashfn || !key); return __rhashtable_insert_fast(ht, key, obj, params, false); } /* 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) { struct rhash_lock_head __rcu **bkt; struct rhash_head __rcu **pprev; struct rhash_head *he; unsigned long flags; unsigned int hash; int err = -ENOENT; hash = rht_head_hashfn(ht, tbl, obj, params); bkt = rht_bucket_var(tbl, hash); if (!bkt) return -ENOENT; pprev = NULL; flags = rht_lock(tbl, bkt); rht_for_each_from(he, rht_ptr(bkt, tbl, hash), tbl, hash) { struct rhlist_head *list; list = container_of(he, struct rhlist_head, rhead); if (he != obj) { struct rhlist_head __rcu **lpprev; pprev = &he->next; if (!rhlist) continue; do { lpprev = &list->next; list = rht_dereference_bucket(list->next, tbl, hash); } while (list && obj != &list->rhead); if (!list) continue; list = rht_dereference_bucket(list->next, tbl, hash); RCU_INIT_POINTER(*lpprev, list); err = 0; break; } obj = rht_dereference_bucket(obj->next, tbl, hash); err = 1; if (rhlist) { list = rht_dereference_bucket(list->next, tbl, hash); if (list) { RCU_INIT_POINTER(list->rhead.next, obj); obj = &list->rhead; err = 0; } } if (pprev) { rcu_assign_pointer(*pprev, obj); rht_unlock(tbl, bkt, flags); } else { rht_assign_unlock(tbl, bkt, obj, flags); } goto unlocked; } rht_unlock(tbl, bkt, flags); unlocked: if (err > 0) { atomic_dec(&ht->nelems); if (unlikely(ht->p.automatic_shrinking && rht_shrink_below_30(ht, tbl))) schedule_work(&ht->run_work); err = 0; } return err; } /* 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) { 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_one(ht, tbl, obj, params, rhlist)) && (tbl = rht_dereference_rcu(tbl->future_tbl, ht))) ; rcu_read_unlock(); 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 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) { return __rhashtable_remove_fast(ht, obj, params, false); } /** * 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) { return __rhashtable_remove_fast(&hlt->ht, &list->rhead, params, true); } /* 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) { struct rhash_lock_head __rcu **bkt; struct rhash_head __rcu **pprev; struct rhash_head *he; unsigned long flags; unsigned int hash; int err = -ENOENT; /* Minimally, the old and new objects must have same hash * (which should mean identifiers are the same). */ hash = rht_head_hashfn(ht, tbl, obj_old, params); if (hash != rht_head_hashfn(ht, tbl, obj_new, params)) return -EINVAL; bkt = rht_bucket_var(tbl, hash); if (!bkt) return -ENOENT; pprev = NULL; flags = rht_lock(tbl, bkt); rht_for_each_from(he, rht_ptr(bkt, tbl, hash), tbl, hash) { if (he != obj_old) { pprev = &he->next; continue; } rcu_assign_pointer(obj_new->next, obj_old->next); if (pprev) { rcu_assign_pointer(*pprev, obj_new); rht_unlock(tbl, bkt, flags); } else { rht_assign_unlock(tbl, bkt, obj_new, flags); } err = 0; goto unlocked; } rht_unlock(tbl, bkt, flags); unlocked: return err; } /** * 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) { 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_replace_fast(ht, tbl, obj_old, obj_new, params)) && (tbl = rht_dereference_rcu(tbl->future_tbl, ht))) ; rcu_read_unlock(); return err; } /** * 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) { return rhashtable_walk_enter(&hlt->ht, 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) { return rhashtable_free_and_destroy(&hlt->ht, free_fn, arg); } static inline void rhltable_destroy(struct rhltable *hlt) { return rhltable_free_and_destroy(hlt, NULL, NULL); } #endif /* _LINUX_RHASHTABLE_H */