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nftables: Convert nft_hash to use generic rhashtable
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The sizing of the hash table and the practice of requiring a lookup
to retrieve the pprev to be stored in the element cookie before the
deletion of an entry is left intact.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Acked-by: Patrick McHardy <kaber@trash.net>
Reviewed-by: Nikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Thomas Graf authored and David S. Miller committed Aug 3, 2014
1 parent e341694 commit cfe4a9d
Showing 1 changed file with 55 additions and 236 deletions.
291 changes: 55 additions & 236 deletions net/netfilter/nft_hash.c
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Original file line number Diff line number Diff line change
Expand Up @@ -15,209 +15,40 @@
#include <linux/log2.h>
#include <linux/jhash.h>
#include <linux/netlink.h>
#include <linux/vmalloc.h>
#include <linux/rhashtable.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nf_tables.h>
#include <net/netfilter/nf_tables.h>

#define NFT_HASH_MIN_SIZE 4UL

struct nft_hash {
struct nft_hash_table __rcu *tbl;
};

struct nft_hash_table {
unsigned int size;
struct nft_hash_elem __rcu *buckets[];
};
/* We target a hash table size of 4, element hint is 75% of final size */
#define NFT_HASH_ELEMENT_HINT 3

struct nft_hash_elem {
struct nft_hash_elem __rcu *next;
struct rhash_head node;
struct nft_data key;
struct nft_data data[];
};

#define nft_hash_for_each_entry(i, head) \
for (i = nft_dereference(head); i != NULL; i = nft_dereference(i->next))
#define nft_hash_for_each_entry_rcu(i, head) \
for (i = rcu_dereference(head); i != NULL; i = rcu_dereference(i->next))

static u32 nft_hash_rnd __read_mostly;
static bool nft_hash_rnd_initted __read_mostly;

static unsigned int nft_hash_data(const struct nft_data *data,
unsigned int hsize, unsigned int len)
{
unsigned int h;

h = jhash(data->data, len, nft_hash_rnd);
return h & (hsize - 1);
}

static bool nft_hash_lookup(const struct nft_set *set,
const struct nft_data *key,
struct nft_data *data)
{
const struct nft_hash *priv = nft_set_priv(set);
const struct nft_hash_table *tbl = rcu_dereference(priv->tbl);
const struct rhashtable *priv = nft_set_priv(set);
const struct nft_hash_elem *he;
unsigned int h;

h = nft_hash_data(key, tbl->size, set->klen);
nft_hash_for_each_entry_rcu(he, tbl->buckets[h]) {
if (nft_data_cmp(&he->key, key, set->klen))
continue;
if (set->flags & NFT_SET_MAP)
nft_data_copy(data, he->data);
return true;
}
return false;
}

static void nft_hash_tbl_free(const struct nft_hash_table *tbl)
{
kvfree(tbl);
}

static unsigned int nft_hash_tbl_size(unsigned int nelem)
{
return max(roundup_pow_of_two(nelem * 4 / 3), NFT_HASH_MIN_SIZE);
}

static struct nft_hash_table *nft_hash_tbl_alloc(unsigned int nbuckets)
{
struct nft_hash_table *tbl;
size_t size;

size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]);
tbl = kzalloc(size, GFP_KERNEL | __GFP_REPEAT | __GFP_NOWARN);
if (tbl == NULL)
tbl = vzalloc(size);
if (tbl == NULL)
return NULL;
tbl->size = nbuckets;

return tbl;
}

static void nft_hash_chain_unzip(const struct nft_set *set,
const struct nft_hash_table *ntbl,
struct nft_hash_table *tbl, unsigned int n)
{
struct nft_hash_elem *he, *last, *next;
unsigned int h;

he = nft_dereference(tbl->buckets[n]);
if (he == NULL)
return;
h = nft_hash_data(&he->key, ntbl->size, set->klen);

/* Find last element of first chain hashing to bucket h */
last = he;
nft_hash_for_each_entry(he, he->next) {
if (nft_hash_data(&he->key, ntbl->size, set->klen) != h)
break;
last = he;
}

/* Unlink first chain from the old table */
RCU_INIT_POINTER(tbl->buckets[n], last->next);

/* If end of chain reached, done */
if (he == NULL)
return;
he = rhashtable_lookup(priv, key);
if (he && set->flags & NFT_SET_MAP)
nft_data_copy(data, he->data);

/* Find first element of second chain hashing to bucket h */
next = NULL;
nft_hash_for_each_entry(he, he->next) {
if (nft_hash_data(&he->key, ntbl->size, set->klen) != h)
continue;
next = he;
break;
}

/* Link the two chains */
RCU_INIT_POINTER(last->next, next);
}

static int nft_hash_tbl_expand(const struct nft_set *set, struct nft_hash *priv)
{
struct nft_hash_table *tbl = nft_dereference(priv->tbl), *ntbl;
struct nft_hash_elem *he;
unsigned int i, h;
bool complete;

ntbl = nft_hash_tbl_alloc(tbl->size * 2);
if (ntbl == NULL)
return -ENOMEM;

/* Link new table's buckets to first element in the old table
* hashing to the new bucket.
*/
for (i = 0; i < ntbl->size; i++) {
h = i < tbl->size ? i : i - tbl->size;
nft_hash_for_each_entry(he, tbl->buckets[h]) {
if (nft_hash_data(&he->key, ntbl->size, set->klen) != i)
continue;
RCU_INIT_POINTER(ntbl->buckets[i], he);
break;
}
}

/* Publish new table */
rcu_assign_pointer(priv->tbl, ntbl);

/* Unzip interleaved hash chains */
do {
/* Wait for readers to use new table/unzipped chains */
synchronize_rcu();

complete = true;
for (i = 0; i < tbl->size; i++) {
nft_hash_chain_unzip(set, ntbl, tbl, i);
if (tbl->buckets[i] != NULL)
complete = false;
}
} while (!complete);

nft_hash_tbl_free(tbl);
return 0;
}

static int nft_hash_tbl_shrink(const struct nft_set *set, struct nft_hash *priv)
{
struct nft_hash_table *tbl = nft_dereference(priv->tbl), *ntbl;
struct nft_hash_elem __rcu **pprev;
unsigned int i;

ntbl = nft_hash_tbl_alloc(tbl->size / 2);
if (ntbl == NULL)
return -ENOMEM;

for (i = 0; i < ntbl->size; i++) {
ntbl->buckets[i] = tbl->buckets[i];

for (pprev = &ntbl->buckets[i]; *pprev != NULL;
pprev = &nft_dereference(*pprev)->next)
;
RCU_INIT_POINTER(*pprev, tbl->buckets[i + ntbl->size]);
}

/* Publish new table */
rcu_assign_pointer(priv->tbl, ntbl);
synchronize_rcu();

nft_hash_tbl_free(tbl);
return 0;
return !!he;
}

static int nft_hash_insert(const struct nft_set *set,
const struct nft_set_elem *elem)
{
struct nft_hash *priv = nft_set_priv(set);
struct nft_hash_table *tbl = nft_dereference(priv->tbl);
struct rhashtable *priv = nft_set_priv(set);
struct nft_hash_elem *he;
unsigned int size, h;
unsigned int size;

if (elem->flags != 0)
return -EINVAL;
Expand All @@ -234,13 +65,7 @@ static int nft_hash_insert(const struct nft_set *set,
if (set->flags & NFT_SET_MAP)
nft_data_copy(he->data, &elem->data);

h = nft_hash_data(&he->key, tbl->size, set->klen);
RCU_INIT_POINTER(he->next, tbl->buckets[h]);
rcu_assign_pointer(tbl->buckets[h], he);

/* Expand table when exceeding 75% load */
if (set->nelems + 1 > tbl->size / 4 * 3)
nft_hash_tbl_expand(set, priv);
rhashtable_insert(priv, &he->node, GFP_KERNEL);

return 0;
}
Expand All @@ -257,36 +82,31 @@ static void nft_hash_elem_destroy(const struct nft_set *set,
static void nft_hash_remove(const struct nft_set *set,
const struct nft_set_elem *elem)
{
struct nft_hash *priv = nft_set_priv(set);
struct nft_hash_table *tbl = nft_dereference(priv->tbl);
struct nft_hash_elem *he, __rcu **pprev;
struct rhashtable *priv = nft_set_priv(set);
struct rhash_head *he, __rcu **pprev;

pprev = elem->cookie;
he = nft_dereference((*pprev));
he = rht_dereference((*pprev), priv);

rhashtable_remove_pprev(priv, he, pprev, GFP_KERNEL);

RCU_INIT_POINTER(*pprev, he->next);
synchronize_rcu();
kfree(he);

/* Shrink table beneath 30% load */
if (set->nelems - 1 < tbl->size * 3 / 10 &&
tbl->size > NFT_HASH_MIN_SIZE)
nft_hash_tbl_shrink(set, priv);
}

static int nft_hash_get(const struct nft_set *set, struct nft_set_elem *elem)
{
const struct nft_hash *priv = nft_set_priv(set);
const struct nft_hash_table *tbl = nft_dereference(priv->tbl);
struct nft_hash_elem __rcu * const *pprev;
const struct rhashtable *priv = nft_set_priv(set);
const struct bucket_table *tbl = rht_dereference_rcu(priv->tbl, priv);
struct rhash_head __rcu * const *pprev;
struct nft_hash_elem *he;
unsigned int h;
u32 h;

h = nft_hash_data(&elem->key, tbl->size, set->klen);
h = rhashtable_hashfn(priv, &elem->key, set->klen);
pprev = &tbl->buckets[h];
nft_hash_for_each_entry(he, tbl->buckets[h]) {
rht_for_each_entry_rcu(he, tbl->buckets[h], node) {
if (nft_data_cmp(&he->key, &elem->key, set->klen)) {
pprev = &he->next;
pprev = &he->node.next;
continue;
}

Expand All @@ -302,14 +122,15 @@ static int nft_hash_get(const struct nft_set *set, struct nft_set_elem *elem)
static void nft_hash_walk(const struct nft_ctx *ctx, const struct nft_set *set,
struct nft_set_iter *iter)
{
const struct nft_hash *priv = nft_set_priv(set);
const struct nft_hash_table *tbl = nft_dereference(priv->tbl);
const struct rhashtable *priv = nft_set_priv(set);
const struct bucket_table *tbl;
const struct nft_hash_elem *he;
struct nft_set_elem elem;
unsigned int i;

tbl = rht_dereference_rcu(priv->tbl, priv);
for (i = 0; i < tbl->size; i++) {
nft_hash_for_each_entry(he, tbl->buckets[i]) {
rht_for_each_entry_rcu(he, tbl->buckets[i], node) {
if (iter->count < iter->skip)
goto cont;

Expand All @@ -329,48 +150,46 @@ static void nft_hash_walk(const struct nft_ctx *ctx, const struct nft_set *set,

static unsigned int nft_hash_privsize(const struct nlattr * const nla[])
{
return sizeof(struct nft_hash);
return sizeof(struct rhashtable);
}

static int lockdep_nfnl_lock_is_held(void)
{
return lockdep_nfnl_is_held(NFNL_SUBSYS_NFTABLES);
}

static int nft_hash_init(const struct nft_set *set,
const struct nft_set_desc *desc,
const struct nlattr * const tb[])
{
struct nft_hash *priv = nft_set_priv(set);
struct nft_hash_table *tbl;
unsigned int size;
struct rhashtable *priv = nft_set_priv(set);
struct rhashtable_params params = {
.nelem_hint = desc->size ? : NFT_HASH_ELEMENT_HINT,
.head_offset = offsetof(struct nft_hash_elem, node),
.key_offset = offsetof(struct nft_hash_elem, key),
.key_len = set->klen,
.hashfn = jhash,
.grow_decision = rht_grow_above_75,
.shrink_decision = rht_shrink_below_30,
.mutex_is_held = lockdep_nfnl_lock_is_held,
};

if (unlikely(!nft_hash_rnd_initted)) {
get_random_bytes(&nft_hash_rnd, 4);
nft_hash_rnd_initted = true;
}

size = NFT_HASH_MIN_SIZE;
if (desc->size)
size = nft_hash_tbl_size(desc->size);

tbl = nft_hash_tbl_alloc(size);
if (tbl == NULL)
return -ENOMEM;
RCU_INIT_POINTER(priv->tbl, tbl);
return 0;
return rhashtable_init(priv, &params);
}

static void nft_hash_destroy(const struct nft_set *set)
{
const struct nft_hash *priv = nft_set_priv(set);
const struct nft_hash_table *tbl = nft_dereference(priv->tbl);
const struct rhashtable *priv = nft_set_priv(set);
const struct bucket_table *tbl;
struct nft_hash_elem *he, *next;
unsigned int i;

for (i = 0; i < tbl->size; i++) {
for (he = nft_dereference(tbl->buckets[i]); he != NULL;
he = next) {
next = nft_dereference(he->next);
tbl = rht_dereference(priv->tbl, priv);
for (i = 0; i < tbl->size; i++)
rht_for_each_entry_safe(he, next, tbl->buckets[i], priv, node)
nft_hash_elem_destroy(set, he);
}
}
kfree(tbl);

rhashtable_destroy(priv);
}

static bool nft_hash_estimate(const struct nft_set_desc *desc, u32 features,
Expand All @@ -383,8 +202,8 @@ static bool nft_hash_estimate(const struct nft_set_desc *desc, u32 features,
esize += FIELD_SIZEOF(struct nft_hash_elem, data[0]);

if (desc->size) {
est->size = sizeof(struct nft_hash) +
nft_hash_tbl_size(desc->size) *
est->size = sizeof(struct rhashtable) +
roundup_pow_of_two(desc->size * 4 / 3) *
sizeof(struct nft_hash_elem *) +
desc->size * esize;
} else {
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