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products/sources/formale Sprachen/C/Linux/include/linux/ (Open Source Betriebssystem Version 6.17.9^©) Datei vom 24.10.2025 mit Größe 37 kB

Quelle rhashtable.h Sprache: C

/* 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)
{
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)
{
rhashtable_free_and_destroy(&hlt->ht, free_fn, arg);
}

static inline void rhltable_destroy(struct rhltable *hlt)
{
rhltable_free_and_destroy(hlt, NULL, NULL);
}

#endif /* _LINUX_RHASHTABLE_H */

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