diff options
| author | Herbert Xu <herbert@gondor.apana.org.au> | 2015-03-24 00:50:21 +1100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-03-23 22:07:51 -0400 |
| commit | 31ccde2dacea8375c3a7d6fffbf0060ee0d40214 (patch) | |
| tree | 82c65efdd9369d9793996e568ada542ab54bc3c7 /include | |
| parent | de91b25c8011089f5dd99b9d24743db1f550ca4b (diff) | |
rhashtable: Allow hashfn to be unset
Since every current rhashtable user uses jhash as their hash
function, the fact that jhash is an inline function causes each
user to generate a copy of its code.
This function provides a solution to this problem by allowing
hashfn to be unset. In which case rhashtable will automatically
set it to jhash. Furthermore, if the key length is a multiple
of 4, we will switch over to jhash2.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/rhashtable.h | 33 |
1 files changed, 27 insertions, 6 deletions
diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h index 3851952781d7..bc2488b98321 100644 --- a/include/linux/rhashtable.h +++ b/include/linux/rhashtable.h @@ -19,6 +19,7 @@ #include <linux/compiler.h> #include <linux/errno.h> +#include <linux/jhash.h> #include <linux/list_nulls.h> #include <linux/workqueue.h> #include <linux/mutex.h> @@ -103,7 +104,7 @@ struct rhashtable; * @min_size: Minimum size while shrinking * @nulls_base: Base value to generate nulls marker * @locks_mul: Number of bucket locks to allocate per cpu (default: 128) - * @hashfn: Function to hash key + * @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 */ @@ -125,6 +126,7 @@ struct rhashtable_params { * struct rhashtable - Hash table handle * @tbl: Bucket table * @nelems: Number of elements in table + * @key_len: Key length for hashfn * @p: Configuration parameters * @run_work: Deferred worker to expand/shrink asynchronously * @mutex: Mutex to protect current/future table swapping @@ -134,6 +136,7 @@ struct rhashtable { struct bucket_table __rcu *tbl; atomic_t nelems; bool being_destroyed; + unsigned int key_len; struct rhashtable_params p; struct work_struct run_work; struct mutex mutex; @@ -199,13 +202,31 @@ static inline unsigned int rht_key_hashfn( struct rhashtable *ht, const struct bucket_table *tbl, const void *key, const struct rhashtable_params params) { + unsigned hash; + /* params must be equal to ht->p if it isn't constant. */ - unsigned key_len = __builtin_constant_p(params.key_len) ? - (params.key_len ?: ht->p.key_len) : - params.key_len; + if (!__builtin_constant_p(params.key_len)) + hash = ht->p.hashfn(key, ht->key_len, tbl->hash_rnd); + else if (params.key_len) { + unsigned key_len = params.key_len; + + if (params.hashfn) + hash = params.hashfn(key, key_len, tbl->hash_rnd); + else if (key_len & (sizeof(u32) - 1)) + hash = jhash(key, key_len, tbl->hash_rnd); + else + hash = jhash2(key, key_len / sizeof(u32), + tbl->hash_rnd); + } else { + unsigned key_len = ht->p.key_len; + + if (params.hashfn) + hash = params.hashfn(key, key_len, tbl->hash_rnd); + else + hash = jhash(key, key_len, tbl->hash_rnd); + } - return rht_bucket_index(tbl, params.hashfn(key, key_len, - tbl->hash_rnd)); + return rht_bucket_index(tbl, hash); } static inline unsigned int rht_head_hashfn( |