nftables: Convert nft_hash to use generic rhashtable

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>

1 files changed, 55 insertions, 236 deletions

diff --git a/net/netfilter/nft_hash.c b/net/netfilter/nft_hash.c
index 4080ed6a072b..28fb8f38e6ba 100644
--- a/net/netfilter/nft_hash.c
+++ b/net/netfilter/nft_hash.c
@@ -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;
@@ -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;
 }
@@ -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;
                 }
 
@@ -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;
 
@@ -329,48 +150,46 @@ cont:
 
 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,
@@ -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 {