Commit 29ba732a authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by David S. Miller
Browse files

bpf: Add BPF_MAP_TYPE_LRU_HASH



Provide a LRU version of the existing BPF_MAP_TYPE_HASH.
Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent fd91de7b
......@@ -85,6 +85,7 @@ enum bpf_map_type {
BPF_MAP_TYPE_PERCPU_ARRAY,
BPF_MAP_TYPE_STACK_TRACE,
BPF_MAP_TYPE_CGROUP_ARRAY,
BPF_MAP_TYPE_LRU_HASH,
};
enum bpf_prog_type {
......@@ -106,6 +107,13 @@ enum bpf_prog_type {
#define BPF_EXIST 2 /* update existing element */
#define BPF_F_NO_PREALLOC (1U << 0)
/* Instead of having one common LRU list in the
* BPF_MAP_TYPE_LRU_HASH map, use a percpu LRU list
* which can scale and perform better.
* Note, the LRU nodes (including free nodes) cannot be moved
* across different LRU lists.
*/
#define BPF_F_NO_COMMON_LRU (1U << 1)
union bpf_attr {
struct { /* anonymous struct used by BPF_MAP_CREATE command */
......
......@@ -15,6 +15,7 @@
#include <linux/filter.h>
#include <linux/vmalloc.h>
#include "percpu_freelist.h"
#include "bpf_lru_list.h"
struct bucket {
struct hlist_head head;
......@@ -25,7 +26,10 @@ struct bpf_htab {
struct bpf_map map;
struct bucket *buckets;
void *elems;
struct pcpu_freelist freelist;
union {
struct pcpu_freelist freelist;
struct bpf_lru lru;
};
void __percpu *extra_elems;
atomic_t count; /* number of elements in this hashtable */
u32 n_buckets; /* number of hash buckets */
......@@ -48,11 +52,19 @@ struct htab_elem {
union {
struct rcu_head rcu;
enum extra_elem_state state;
struct bpf_lru_node lru_node;
};
u32 hash;
char key[0] __aligned(8);
};
static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node);
static bool htab_is_lru(const struct bpf_htab *htab)
{
return htab->map.map_type == BPF_MAP_TYPE_LRU_HASH;
}
static inline void htab_elem_set_ptr(struct htab_elem *l, u32 key_size,
void __percpu *pptr)
{
......@@ -87,7 +99,22 @@ static void htab_free_elems(struct bpf_htab *htab)
vfree(htab->elems);
}
static int prealloc_elems_and_freelist(struct bpf_htab *htab)
static struct htab_elem *prealloc_lru_pop(struct bpf_htab *htab, void *key,
u32 hash)
{
struct bpf_lru_node *node = bpf_lru_pop_free(&htab->lru, hash);
struct htab_elem *l;
if (node) {
l = container_of(node, struct htab_elem, lru_node);
memcpy(l->key, key, htab->map.key_size);
return l;
}
return NULL;
}
static int prealloc_init(struct bpf_htab *htab)
{
int err = -ENOMEM, i;
......@@ -110,12 +137,27 @@ static int prealloc_elems_and_freelist(struct bpf_htab *htab)
}
skip_percpu_elems:
err = pcpu_freelist_init(&htab->freelist);
if (htab_is_lru(htab))
err = bpf_lru_init(&htab->lru,
htab->map.map_flags & BPF_F_NO_COMMON_LRU,
offsetof(struct htab_elem, hash) -
offsetof(struct htab_elem, lru_node),
htab_lru_map_delete_node,
htab);
else
err = pcpu_freelist_init(&htab->freelist);
if (err)
goto free_elems;
pcpu_freelist_populate(&htab->freelist, htab->elems, htab->elem_size,
htab->map.max_entries);
if (htab_is_lru(htab))
bpf_lru_populate(&htab->lru, htab->elems,
offsetof(struct htab_elem, lru_node),
htab->elem_size, htab->map.max_entries);
else
pcpu_freelist_populate(&htab->freelist, htab->elems,
htab->elem_size, htab->map.max_entries);
return 0;
free_elems:
......@@ -123,6 +165,16 @@ static int prealloc_elems_and_freelist(struct bpf_htab *htab)
return err;
}
static void prealloc_destroy(struct bpf_htab *htab)
{
htab_free_elems(htab);
if (htab_is_lru(htab))
bpf_lru_destroy(&htab->lru);
else
pcpu_freelist_destroy(&htab->freelist);
}
static int alloc_extra_elems(struct bpf_htab *htab)
{
void __percpu *pptr;
......@@ -144,14 +196,34 @@ static int alloc_extra_elems(struct bpf_htab *htab)
static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
{
bool percpu = attr->map_type == BPF_MAP_TYPE_PERCPU_HASH;
bool lru = attr->map_type == BPF_MAP_TYPE_LRU_HASH;
/* percpu_lru means each cpu has its own LRU list.
* it is different from BPF_MAP_TYPE_PERCPU_HASH where
* the map's value itself is percpu. percpu_lru has
* nothing to do with the map's value.
*/
bool percpu_lru = (attr->map_flags & BPF_F_NO_COMMON_LRU);
bool prealloc = !(attr->map_flags & BPF_F_NO_PREALLOC);
struct bpf_htab *htab;
int err, i;
u64 cost;
if (attr->map_flags & ~BPF_F_NO_PREALLOC)
if (lru && !capable(CAP_SYS_ADMIN))
/* LRU implementation is much complicated than other
* maps. Hence, limit to CAP_SYS_ADMIN for now.
*/
return ERR_PTR(-EPERM);
if (attr->map_flags & ~(BPF_F_NO_PREALLOC | BPF_F_NO_COMMON_LRU))
/* reserved bits should not be used */
return ERR_PTR(-EINVAL);
if (!lru && percpu_lru)
return ERR_PTR(-EINVAL);
if (lru && !prealloc)
return ERR_PTR(-ENOTSUPP);
htab = kzalloc(sizeof(*htab), GFP_USER);
if (!htab)
return ERR_PTR(-ENOMEM);
......@@ -171,6 +243,18 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
htab->map.value_size == 0)
goto free_htab;
if (percpu_lru) {
/* ensure each CPU's lru list has >=1 elements.
* since we are at it, make each lru list has the same
* number of elements.
*/
htab->map.max_entries = roundup(attr->max_entries,
num_possible_cpus());
if (htab->map.max_entries < attr->max_entries)
htab->map.max_entries = rounddown(attr->max_entries,
num_possible_cpus());
}
/* hash table size must be power of 2 */
htab->n_buckets = roundup_pow_of_two(htab->map.max_entries);
......@@ -241,14 +325,17 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
raw_spin_lock_init(&htab->buckets[i].lock);
}
if (!percpu) {
if (!percpu && !lru) {
/* lru itself can remove the least used element, so
* there is no need for an extra elem during map_update.
*/
err = alloc_extra_elems(htab);
if (err)
goto free_buckets;
}
if (!(attr->map_flags & BPF_F_NO_PREALLOC)) {
err = prealloc_elems_and_freelist(htab);
if (prealloc) {
err = prealloc_init(htab);
if (err)
goto free_extra_elems;
}
......@@ -323,6 +410,46 @@ static void *htab_map_lookup_elem(struct bpf_map *map, void *key)
return NULL;
}
static void *htab_lru_map_lookup_elem(struct bpf_map *map, void *key)
{
struct htab_elem *l = __htab_map_lookup_elem(map, key);
if (l) {
bpf_lru_node_set_ref(&l->lru_node);
return l->key + round_up(map->key_size, 8);
}
return NULL;
}
/* It is called from the bpf_lru_list when the LRU needs to delete
* older elements from the htab.
*/
static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node)
{
struct bpf_htab *htab = (struct bpf_htab *)arg;
struct htab_elem *l, *tgt_l;
struct hlist_head *head;
unsigned long flags;
struct bucket *b;
tgt_l = container_of(node, struct htab_elem, lru_node);
b = __select_bucket(htab, tgt_l->hash);
head = &b->head;
raw_spin_lock_irqsave(&b->lock, flags);
hlist_for_each_entry_rcu(l, head, hash_node)
if (l == tgt_l) {
hlist_del_rcu(&l->hash_node);
break;
}
raw_spin_unlock_irqrestore(&b->lock, flags);
return l == tgt_l;
}
/* Called from syscall */
static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
{
......@@ -579,6 +706,70 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
return ret;
}
static int htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value,
u64 map_flags)
{
struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
struct htab_elem *l_new, *l_old = NULL;
struct hlist_head *head;
unsigned long flags;
struct bucket *b;
u32 key_size, hash;
int ret;
if (unlikely(map_flags > BPF_EXIST))
/* unknown flags */
return -EINVAL;
WARN_ON_ONCE(!rcu_read_lock_held());
key_size = map->key_size;
hash = htab_map_hash(key, key_size);
b = __select_bucket(htab, hash);
head = &b->head;
/* For LRU, we need to alloc before taking bucket's
* spinlock because getting free nodes from LRU may need
* to remove older elements from htab and this removal
* operation will need a bucket lock.
*/
l_new = prealloc_lru_pop(htab, key, hash);
if (!l_new)
return -ENOMEM;
memcpy(l_new->key + round_up(map->key_size, 8), value, map->value_size);
/* bpf_map_update_elem() can be called in_irq() */
raw_spin_lock_irqsave(&b->lock, flags);
l_old = lookup_elem_raw(head, hash, key, key_size);
ret = check_flags(htab, l_old, map_flags);
if (ret)
goto err;
/* add new element to the head of the list, so that
* concurrent search will find it before old elem
*/
hlist_add_head_rcu(&l_new->hash_node, head);
if (l_old) {
bpf_lru_node_set_ref(&l_new->lru_node);
hlist_del_rcu(&l_old->hash_node);
}
ret = 0;
err:
raw_spin_unlock_irqrestore(&b->lock, flags);
if (ret)
bpf_lru_push_free(&htab->lru, &l_new->lru_node);
else if (l_old)
bpf_lru_push_free(&htab->lru, &l_old->lru_node);
return ret;
}
static int __htab_percpu_map_update_elem(struct bpf_map *map, void *key,
void *value, u64 map_flags,
bool onallcpus)
......@@ -671,6 +862,39 @@ static int htab_map_delete_elem(struct bpf_map *map, void *key)
return ret;
}
static int htab_lru_map_delete_elem(struct bpf_map *map, void *key)
{
struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
struct hlist_head *head;
struct bucket *b;
struct htab_elem *l;
unsigned long flags;
u32 hash, key_size;
int ret = -ENOENT;
WARN_ON_ONCE(!rcu_read_lock_held());
key_size = map->key_size;
hash = htab_map_hash(key, key_size);
b = __select_bucket(htab, hash);
head = &b->head;
raw_spin_lock_irqsave(&b->lock, flags);
l = lookup_elem_raw(head, hash, key, key_size);
if (l) {
hlist_del_rcu(&l->hash_node);
ret = 0;
}
raw_spin_unlock_irqrestore(&b->lock, flags);
if (l)
bpf_lru_push_free(&htab->lru, &l->lru_node);
return ret;
}
static void delete_all_elements(struct bpf_htab *htab)
{
int i;
......@@ -703,12 +927,11 @@ static void htab_map_free(struct bpf_map *map)
* not have executed. Wait for them.
*/
rcu_barrier();
if (htab->map.map_flags & BPF_F_NO_PREALLOC) {
if (htab->map.map_flags & BPF_F_NO_PREALLOC)
delete_all_elements(htab);
} else {
htab_free_elems(htab);
pcpu_freelist_destroy(&htab->freelist);
}
else
prealloc_destroy(htab);
free_percpu(htab->extra_elems);
kvfree(htab->buckets);
kfree(htab);
......@@ -728,6 +951,20 @@ static struct bpf_map_type_list htab_type __read_mostly = {
.type = BPF_MAP_TYPE_HASH,
};
static const struct bpf_map_ops htab_lru_ops = {
.map_alloc = htab_map_alloc,
.map_free = htab_map_free,
.map_get_next_key = htab_map_get_next_key,
.map_lookup_elem = htab_lru_map_lookup_elem,
.map_update_elem = htab_lru_map_update_elem,
.map_delete_elem = htab_lru_map_delete_elem,
};
static struct bpf_map_type_list htab_lru_type __read_mostly = {
.ops = &htab_lru_ops,
.type = BPF_MAP_TYPE_LRU_HASH,
};
/* Called from eBPF program */
static void *htab_percpu_map_lookup_elem(struct bpf_map *map, void *key)
{
......@@ -798,6 +1035,7 @@ static int __init register_htab_map(void)
{
bpf_register_map_type(&htab_type);
bpf_register_map_type(&htab_percpu_type);
bpf_register_map_type(&htab_lru_type);
return 0;
}
late_initcall(register_htab_map);
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