diff options
Diffstat (limited to 'include/linux/rhashtable.h')
| -rw-r--r-- | include/linux/rhashtable.h | 43 |
1 files changed, 38 insertions, 5 deletions
diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h index 092292b6675e..ae87dcdf52d2 100644 --- a/include/linux/rhashtable.h +++ b/include/linux/rhashtable.h @@ -49,6 +49,21 @@ /* Base bits plus 1 bit for nulls marker */ #define RHT_HASH_RESERVED_SPACE (RHT_BASE_BITS + 1) +/* 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 rhash_head { struct rhash_head __rcu *next; }; @@ -114,7 +129,6 @@ struct rhashtable; * @max_size: Maximum size while expanding * @min_size: Minimum size while shrinking * @nulls_base: Base value to generate nulls marker - * @insecure_elasticity: Set to true to disable chain length checks * @automatic_shrinking: Enable automatic shrinking of tables * @locks_mul: Number of bucket locks to allocate per cpu (default: 128) * @hashfn: Hash function (default: jhash2 if !(key_len % 4), or jhash) @@ -130,7 +144,6 @@ struct rhashtable_params { unsigned int max_size; unsigned int min_size; u32 nulls_base; - bool insecure_elasticity; bool automatic_shrinking; size_t locks_mul; rht_hashfn_t hashfn; @@ -143,7 +156,6 @@ struct rhashtable_params { * @tbl: Bucket table * @nelems: Number of elements in table * @key_len: Key length for hashfn - * @elasticity: Maximum chain length before rehash * @p: Configuration parameters * @rhlist: True if this is an rhltable * @run_work: Deferred worker to expand/shrink asynchronously @@ -154,7 +166,6 @@ struct rhashtable { struct bucket_table __rcu *tbl; atomic_t nelems; unsigned int key_len; - unsigned int elasticity; struct rhashtable_params p; bool rhlist; struct work_struct run_work; @@ -726,7 +737,7 @@ slow_path: return rhashtable_insert_slow(ht, key, obj); } - elasticity = ht->elasticity; + elasticity = RHT_ELASTICITY; pprev = rht_bucket_insert(ht, tbl, hash); data = ERR_PTR(-ENOMEM); if (!pprev) @@ -916,6 +927,28 @@ static inline int rhashtable_lookup_insert_fast( } /** + * 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 |