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rhashtable: Add rhashtable_lookup()

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Extracted from commit ca26893f05e8 "rhashtable: Add rhlist interface".

Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ben Hutchings 2018-12-07 17:16:46 +00:00 committed by Greg Kroah-Hartman
parent 8295999786
commit 9e5f4d0b79
1 changed files with 52 additions and 17 deletions
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69
include/linux/rhashtable.h
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@ -515,18 +515,8 @@ static inline int rhashtable_compare(struct rhashtable_compare_arg *arg,
return memcmp(ptr + ht->p.key_offset, arg->key, ht->p.key_len);
}
/**
* rhashtable_lookup_fast - search hash table, inlined version
* @ht: hash table
* @key: the pointer to the key
* @params: hash table parameters
*
* Computes the hash value for the key and traverses the bucket chain looking
* for a entry with an identical key. The first matching entry is returned.
*
* Returns the first entry on which the compare function returned true.
*/
static inline void *rhashtable_lookup_fast(
/* Internal function, do not use. */
static inline struct rhash_head *__rhashtable_lookup(
struct rhashtable *ht, const void *key,
const struct rhashtable_params params)
{
@ -538,8 +528,6 @@ static inline void *rhashtable_lookup_fast(
struct rhash_head *he;
unsigned int hash;
rcu_read_lock();
tbl = rht_dereference_rcu(ht->tbl, ht);
restart:
hash = rht_key_hashfn(ht, tbl, key, params);
@ -548,8 +536,7 @@ restart:
params.obj_cmpfn(&arg, rht_obj(ht, he)) :
rhashtable_compare(&arg, rht_obj(ht, he)))
continue;
rcu_read_unlock();
return rht_obj(ht, he);
return he;
}
/* Ensure we see any new tables. */
@ -558,11 +545,59 @@ restart:
tbl = rht_dereference_rcu(tbl->future_tbl, ht);
if (unlikely(tbl))
goto restart;
rcu_read_unlock();
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;
}
/* 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().