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rhashtable: remove nulls_base and related code.

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This "feature" is unused, undocumented, and untested and so doesn't
really belong.  A patch is under development to properly implement
support for detecting when a search gets diverted down a different
chain, which the common purpose of nulls markers.

This patch actually fixes a bug too.  The table resizing allows a
table to grow to 2^31 buckets, but the hash is truncated to 27 bits -
any growth beyond 2^27 is wasteful an ineffective.

This patch results in NULLS_MARKER(0) being used for all chains,
and leaves the use of rht_is_a_null() to test for it.

Acked-by: Herbert Xu <[email protected]>
Signed-off-by: NeilBrown <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
This commit is contained in:
NeilBrown 2018-06-18 12:52:50 +10:00 • committed by David S. Miller
commit 9f9a707738
5 changed files with 6 additions and 46 deletions
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8
lib/rhashtable.c
View file

@ -995,7 +995,6 @@ static u32 rhashtable_jhash2(const void *key, u32 length, u32 seed)
* .key_offset = offsetof(struct test_obj, key),
* .key_len = sizeof(int),
* .hashfn = jhash,
* .nulls_base = (1U << RHT_BASE_SHIFT),
* };
*
* Configuration Example 2: Variable length keys
@ -1029,9 +1028,6 @@ int rhashtable_init(struct rhashtable *ht,
(params->obj_hashfn && !params->obj_cmpfn))
return -EINVAL;
if (params->nulls_base && params->nulls_base < (1U << RHT_BASE_SHIFT))
return -EINVAL;
memset(ht, 0, sizeof(*ht));
mutex_init(&ht->mutex);
spin_lock_init(&ht->lock);
@ -1096,10 +1092,6 @@ int rhltable_init(struct rhltable *hlt, const struct rhashtable_params *params)
{
int err;
/* No rhlist NULLs marking for now. */
if (params->nulls_base)
return -EINVAL;
err = rhashtable_init(&hlt->ht, params);
hlt->ht.rhlist = true;
return err;

5
lib/test_rhashtable.c
View file

@ -83,7 +83,7 @@ static u32 my_hashfn(const void *data, u32 len, u32 seed)
{
const struct test_obj_rhl *obj = data;
return (obj->value.id % 10) << RHT_HASH_RESERVED_SPACE;
return (obj->value.id % 10);
}
static int my_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
@ -99,7 +99,6 @@ static struct rhashtable_params test_rht_params = {
.key_offset = offsetof(struct test_obj, value),
.key_len = sizeof(struct test_obj_val),
.hashfn = jhash,
.nulls_base = (3U << RHT_BASE_SHIFT),
};
static struct rhashtable_params test_rht_params_dup = {
@ -296,8 +295,6 @@ static int __init test_rhltable(unsigned int entries)
if (!obj_in_table)
goto out_free;
/* nulls_base not supported in rhlist interface */
test_rht_params.nulls_base = 0;
err = rhltable_init(&rhlt, &test_rht_params);
if (WARN_ON(err))
goto out_free;