Commit 988dfbd7 authored by Herbert Xu's avatar Herbert Xu Committed by David S. Miller

rhashtable: Move hash_rnd into bucket_table

Currently hash_rnd is a parameter that users can set.  However,
no existing users set this parameter.  It is also something that
people are unlikely to want to set directly since it's just a
random number.

In preparation for allowing the reseeding/rehashing of rhashtable,
this patch moves hash_rnd into bucket_table so that it's now an
internal state rather than a parameter.
Signed-off-by: default avatarHerbert Xu <>
Acked-by: default avatarThomas Graf <>
Signed-off-by: default avatarDavid S. Miller <>
parent 0ddcf43d
......@@ -49,12 +49,14 @@ struct rhash_head {
* struct bucket_table - Table of hash buckets
* @size: Number of hash buckets
* @hash_rnd: Random seed to fold into hash
* @locks_mask: Mask to apply before accessing locks[]
* @locks: Array of spinlocks protecting individual buckets
* @buckets: size * hash buckets
struct bucket_table {
size_t size;
u32 hash_rnd;
unsigned int locks_mask;
spinlock_t *locks;
......@@ -72,7 +74,6 @@ 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
* @hash_rnd: Seed to use while hashing
* @max_shift: Maximum number of shifts while expanding
* @min_shift: Minimum number of shifts while shrinking
* @nulls_base: Base value to generate nulls marker
......@@ -85,7 +86,6 @@ struct rhashtable_params {
size_t key_len;
size_t key_offset;
size_t head_offset;
u32 hash_rnd;
size_t max_shift;
size_t min_shift;
u32 nulls_base;
......@@ -66,25 +66,28 @@ static u32 rht_bucket_index(const struct bucket_table *tbl, u32 hash)
return hash & (tbl->size - 1);
static u32 obj_raw_hashfn(const struct rhashtable *ht, const void *ptr)
static u32 obj_raw_hashfn(struct rhashtable *ht, const void *ptr)
struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht);
u32 hash;
if (unlikely(!ht->p.key_len))
hash = ht->p.obj_hashfn(ptr, ht->p.hash_rnd);
hash = ht->p.obj_hashfn(ptr, tbl->hash_rnd);
hash = ht->p.hashfn(ptr + ht->p.key_offset, ht->p.key_len,
return hash >> HASH_RESERVED_SPACE;
static u32 key_hashfn(struct rhashtable *ht, const void *key, u32 len)
return ht->p.hashfn(key, len, ht->p.hash_rnd) >> HASH_RESERVED_SPACE;
struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht);
return ht->p.hashfn(key, len, tbl->hash_rnd) >> HASH_RESERVED_SPACE;
static u32 head_hashfn(const struct rhashtable *ht,
static u32 head_hashfn(struct rhashtable *ht,
const struct bucket_table *tbl,
const struct rhash_head *he)
......@@ -92,7 +95,7 @@ static u32 head_hashfn(const struct rhashtable *ht,
static void debug_dump_buckets(const struct rhashtable *ht,
static void debug_dump_buckets(struct rhashtable *ht,
const struct bucket_table *tbl)
struct rhash_head *he;
......@@ -385,6 +388,8 @@ int rhashtable_expand(struct rhashtable *ht)
if (new_tbl == NULL)
return -ENOMEM;
new_tbl->hash_rnd = old_tbl->hash_rnd;
/* Make insertions go into the new, empty table right away. Deletions
......@@ -476,6 +481,8 @@ int rhashtable_shrink(struct rhashtable *ht)
if (new_tbl == NULL)
return -ENOMEM;
new_tbl->hash_rnd = tbl->hash_rnd;
rcu_assign_pointer(ht->future_tbl, new_tbl);
......@@ -1099,14 +1106,13 @@ int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params)
if (tbl == NULL)
return -ENOMEM;
get_random_bytes(&tbl->hash_rnd, sizeof(tbl->hash_rnd));
atomic_set(&ht->nelems, 0);
atomic_set(&ht->shift, ilog2(tbl->size));
RCU_INIT_POINTER(ht->tbl, tbl);
RCU_INIT_POINTER(ht->future_tbl, tbl);
if (!ht->p.hash_rnd)
get_random_bytes(&ht->p.hash_rnd, sizeof(ht->p.hash_rnd));
INIT_WORK(&ht->run_work, rht_deferred_worker);
return 0;
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