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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 void rht_lock(struct bucket_table *tbl,
                 struct rhash_lock_head __rcu **bkt)
 {
     local_bh_disable();
     bit_spin_lock(0, (unsigned long *)bkt);
     lock_map_acquire(&tbl->dep_map);
 }
 
 static inline void rht_lock_nested(struct bucket_table *tbl,
                    struct rhash_lock_head __rcu **bucket,
                    unsigned int subclass)
 {
     local_bh_disable();
     bit_spin_lock(0, (unsigned long *)bucket);
     lock_acquire_exclusive(&tbl->dep_map, subclass, 0, NULL, _THIS_IP_);
 }
 
 static inline void rht_unlock(struct bucket_table *tbl,
                   struct rhash_lock_head __rcu **bkt)
 {
     lock_map_release(&tbl->dep_map);
     bit_spin_unlock(0, (unsigned long *)bkt);
     local_bh_enable();
 }
 
 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)
 {
     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_bh_enable();
 }
 
 /**
  * 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 a 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 a 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 a 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 in 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 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;
     rht_lock(tbl, bkt);
 
     if (unlikely(rcu_access_pointer(tbl->future_tbl))) {
 slow_path:
         rht_unlock(tbl, bkt);
         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);
         } else
             rht_assign_unlock(tbl, bkt, obj);
         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);
 
     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);
     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 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;
     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);
         } else {
             rht_assign_unlock(tbl, bkt, obj);
         }
         goto unlocked;
     }
 
     rht_unlock(tbl, bkt);
 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
  * 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 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 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;
     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);
         } else {
             rht_assign_unlock(tbl, bkt, obj_new);
         }
         err = 0;
         goto unlocked;
     }
 
     rht_unlock(tbl, bkt);
 
 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 */

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