diff options
| -rw-r--r-- | include/linux/rhashtable.h | 21 | ||||
| -rw-r--r-- | lib/rhashtable.c | 17 |
2 files changed, 17 insertions, 21 deletions
diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h index e507290cd2c7..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) diff --git a/lib/rhashtable.c b/lib/rhashtable.c index f8635fd57442..d22a5ef109fb 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -535,7 +535,7 @@ static void *rhashtable_lookup_one(struct rhashtable *ht, struct rhash_head *head; int elasticity; - elasticity = ht->elasticity; + elasticity = RHT_ELASTICITY; pprev = rht_bucket_var(tbl, hash); rht_for_each_continue(head, *pprev, tbl, hash) { struct rhlist_head *list; @@ -972,21 +972,6 @@ int rhashtable_init(struct rhashtable *ht, if (params->nelem_hint) size = rounded_hashtable_size(&ht->p); - /* 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. - */ - if (!params->insecure_elasticity) - ht->elasticity = 16; - if (params->locks_mul) ht->p.locks_mul = roundup_pow_of_two(params->locks_mul); else |