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authorMartin KaFai Lau <kafai@fb.com>2016-11-11 10:55:09 -0800
committerDavid S. Miller <davem@davemloft.net>2016-11-15 11:50:20 -0500
commit29ba732acbeece1e34c68483d1ec1f3720fa1bb3 (patch)
tree31274a2c9d6b8bda6cc14253d0781f6462974dd1
parentfd91de7b3c69a7f108b92521e1115df3e058af55 (diff)
bpf: Add BPF_MAP_TYPE_LRU_HASH
Provide a LRU version of the existing BPF_MAP_TYPE_HASH. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--include/uapi/linux/bpf.h8
-rw-r--r--kernel/bpf/hashtab.c266
2 files changed, 260 insertions, 14 deletions
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index e2f38e0..ed8c679 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -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 */
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index b478d80..4a9e71a 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -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 @@ free_elems:
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 @@ free_elems:
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 @@ err:
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);