diff options
Diffstat (limited to 'include/linux/rhashtable.h')
| -rw-r--r-- | include/linux/rhashtable.h | 68 |
1 files changed, 50 insertions, 18 deletions
diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h index 092292b6675e..7d56a7ea2b2e 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; }; @@ -110,29 +125,25 @@ struct rhashtable; * @key_len: Length of key * @key_offset: Offset of key in struct to be hashed * @head_offset: Offset of rhash_head in struct to be hashed - * @insecure_max_entries: Maximum number of entries (may be exceeded) * @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) + * @automatic_shrinking: Enable automatic shrinking of tables + * @nulls_base: Base value to generate nulls marker * @hashfn: Hash function (default: jhash2 if !(key_len % 4), or jhash) * @obj_hashfn: Function to hash object * @obj_cmpfn: Function to compare key with object */ struct rhashtable_params { - size_t nelem_hint; - size_t key_len; - size_t key_offset; - size_t head_offset; - unsigned int insecure_max_entries; + u16 nelem_hint; + u16 key_len; + u16 key_offset; + u16 head_offset; unsigned int max_size; - unsigned int min_size; - u32 nulls_base; - bool insecure_elasticity; + u16 min_size; bool automatic_shrinking; - size_t locks_mul; + u8 locks_mul; + u32 nulls_base; rht_hashfn_t hashfn; rht_obj_hashfn_t obj_hashfn; rht_obj_cmpfn_t obj_cmpfn; @@ -143,8 +154,8 @@ 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 + * @max_elems: Maximum number of elements in table * @rhlist: True if this is an rhltable * @run_work: Deferred worker to expand/shrink asynchronously * @mutex: Mutex to protect current/future table swapping @@ -154,8 +165,8 @@ struct rhashtable { struct bucket_table __rcu *tbl; atomic_t nelems; unsigned int key_len; - unsigned int elasticity; struct rhashtable_params p; + unsigned int max_elems; bool rhlist; struct work_struct run_work; struct mutex mutex; @@ -318,8 +329,7 @@ static inline bool rht_grow_above_100(const struct rhashtable *ht, static inline bool rht_grow_above_max(const struct rhashtable *ht, const struct bucket_table *tbl) { - return ht->p.insecure_max_entries && - atomic_read(&ht->nelems) >= ht->p.insecure_max_entries; + return atomic_read(&ht->nelems) >= ht->max_elems; } /* The bucket lock is selected based on the hash and protects mutations @@ -726,7 +736,7 @@ 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 +926,28 @@ 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 |