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>
This commit is contained in:
Martin KaFai Lau
David S. Miller
parent
fd91de7b3c
commit
29ba732acb
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@ -85,6 +85,7 @@ enum bpf_map_type {
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BPF_MAP_TYPE_PERCPU_ARRAY,
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BPF_MAP_TYPE_STACK_TRACE,
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BPF_MAP_TYPE_CGROUP_ARRAY,
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BPF_MAP_TYPE_LRU_HASH,
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};
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enum bpf_prog_type {
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@ -106,6 +107,13 @@ enum bpf_prog_type {
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#define BPF_EXIST 2 /* update existing element */
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#define BPF_F_NO_PREALLOC (1U << 0)
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/* Instead of having one common LRU list in the
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* BPF_MAP_TYPE_LRU_HASH map, use a percpu LRU list
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* which can scale and perform better.
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* Note, the LRU nodes (including free nodes) cannot be moved
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* across different LRU lists.
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*/
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#define BPF_F_NO_COMMON_LRU (1U << 1)
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union bpf_attr {
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struct { /* anonymous struct used by BPF_MAP_CREATE command */
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@ -15,6 +15,7 @@
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#include <linux/filter.h>
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#include <linux/vmalloc.h>
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#include "percpu_freelist.h"
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#include "bpf_lru_list.h"
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struct bucket {
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struct hlist_head head;
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@ -25,7 +26,10 @@ struct bpf_htab {
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struct bpf_map map;
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struct bucket *buckets;
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void *elems;
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union {
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struct pcpu_freelist freelist;
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struct bpf_lru lru;
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};
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void __percpu *extra_elems;
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atomic_t count; /* number of elements in this hashtable */
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u32 n_buckets; /* number of hash buckets */
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@ -48,11 +52,19 @@ struct htab_elem {
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union {
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struct rcu_head rcu;
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enum extra_elem_state state;
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struct bpf_lru_node lru_node;
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};
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u32 hash;
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char key[0] __aligned(8);
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};
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static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node);
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static bool htab_is_lru(const struct bpf_htab *htab)
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{
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return htab->map.map_type == BPF_MAP_TYPE_LRU_HASH;
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}
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static inline void htab_elem_set_ptr(struct htab_elem *l, u32 key_size,
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void __percpu *pptr)
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{
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@ -87,7 +99,22 @@ free_elems:
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vfree(htab->elems);
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}
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static int prealloc_elems_and_freelist(struct bpf_htab *htab)
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static struct htab_elem *prealloc_lru_pop(struct bpf_htab *htab, void *key,
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u32 hash)
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{
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struct bpf_lru_node *node = bpf_lru_pop_free(&htab->lru, hash);
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struct htab_elem *l;
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if (node) {
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l = container_of(node, struct htab_elem, lru_node);
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memcpy(l->key, key, htab->map.key_size);
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return l;
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}
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return NULL;
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}
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static int prealloc_init(struct bpf_htab *htab)
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{
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int err = -ENOMEM, i;
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@ -110,12 +137,27 @@ static int prealloc_elems_and_freelist(struct bpf_htab *htab)
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}
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skip_percpu_elems:
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if (htab_is_lru(htab))
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err = bpf_lru_init(&htab->lru,
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htab->map.map_flags & BPF_F_NO_COMMON_LRU,
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offsetof(struct htab_elem, hash) -
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offsetof(struct htab_elem, lru_node),
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htab_lru_map_delete_node,
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htab);
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else
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err = pcpu_freelist_init(&htab->freelist);
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if (err)
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goto free_elems;
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pcpu_freelist_populate(&htab->freelist, htab->elems, htab->elem_size,
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htab->map.max_entries);
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if (htab_is_lru(htab))
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bpf_lru_populate(&htab->lru, htab->elems,
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offsetof(struct htab_elem, lru_node),
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htab->elem_size, htab->map.max_entries);
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else
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pcpu_freelist_populate(&htab->freelist, htab->elems,
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htab->elem_size, htab->map.max_entries);
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return 0;
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free_elems:
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@ -123,6 +165,16 @@ free_elems:
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return err;
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}
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static void prealloc_destroy(struct bpf_htab *htab)
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{
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htab_free_elems(htab);
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if (htab_is_lru(htab))
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bpf_lru_destroy(&htab->lru);
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else
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pcpu_freelist_destroy(&htab->freelist);
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}
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static int alloc_extra_elems(struct bpf_htab *htab)
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{
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void __percpu *pptr;
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@ -144,14 +196,34 @@ static int alloc_extra_elems(struct bpf_htab *htab)
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static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
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{
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bool percpu = attr->map_type == BPF_MAP_TYPE_PERCPU_HASH;
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bool lru = attr->map_type == BPF_MAP_TYPE_LRU_HASH;
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/* percpu_lru means each cpu has its own LRU list.
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* it is different from BPF_MAP_TYPE_PERCPU_HASH where
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* the map's value itself is percpu. percpu_lru has
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* nothing to do with the map's value.
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*/
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bool percpu_lru = (attr->map_flags & BPF_F_NO_COMMON_LRU);
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bool prealloc = !(attr->map_flags & BPF_F_NO_PREALLOC);
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struct bpf_htab *htab;
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int err, i;
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u64 cost;
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if (attr->map_flags & ~BPF_F_NO_PREALLOC)
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if (lru && !capable(CAP_SYS_ADMIN))
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/* LRU implementation is much complicated than other
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* maps. Hence, limit to CAP_SYS_ADMIN for now.
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*/
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return ERR_PTR(-EPERM);
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if (attr->map_flags & ~(BPF_F_NO_PREALLOC | BPF_F_NO_COMMON_LRU))
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/* reserved bits should not be used */
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return ERR_PTR(-EINVAL);
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if (!lru && percpu_lru)
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return ERR_PTR(-EINVAL);
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if (lru && !prealloc)
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return ERR_PTR(-ENOTSUPP);
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htab = kzalloc(sizeof(*htab), GFP_USER);
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if (!htab)
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return ERR_PTR(-ENOMEM);
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@ -171,6 +243,18 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
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htab->map.value_size == 0)
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goto free_htab;
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if (percpu_lru) {
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/* ensure each CPU's lru list has >=1 elements.
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* since we are at it, make each lru list has the same
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* number of elements.
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*/
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htab->map.max_entries = roundup(attr->max_entries,
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num_possible_cpus());
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if (htab->map.max_entries < attr->max_entries)
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htab->map.max_entries = rounddown(attr->max_entries,
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num_possible_cpus());
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}
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/* hash table size must be power of 2 */
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htab->n_buckets = roundup_pow_of_two(htab->map.max_entries);
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@ -241,14 +325,17 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
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raw_spin_lock_init(&htab->buckets[i].lock);
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}
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if (!percpu) {
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if (!percpu && !lru) {
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/* lru itself can remove the least used element, so
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* there is no need for an extra elem during map_update.
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*/
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err = alloc_extra_elems(htab);
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if (err)
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goto free_buckets;
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}
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if (!(attr->map_flags & BPF_F_NO_PREALLOC)) {
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err = prealloc_elems_and_freelist(htab);
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if (prealloc) {
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err = prealloc_init(htab);
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if (err)
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goto free_extra_elems;
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}
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@ -323,6 +410,46 @@ static void *htab_map_lookup_elem(struct bpf_map *map, void *key)
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return NULL;
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}
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static void *htab_lru_map_lookup_elem(struct bpf_map *map, void *key)
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{
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struct htab_elem *l = __htab_map_lookup_elem(map, key);
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if (l) {
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bpf_lru_node_set_ref(&l->lru_node);
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return l->key + round_up(map->key_size, 8);
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}
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return NULL;
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}
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/* It is called from the bpf_lru_list when the LRU needs to delete
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* older elements from the htab.
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*/
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static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node)
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{
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struct bpf_htab *htab = (struct bpf_htab *)arg;
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struct htab_elem *l, *tgt_l;
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struct hlist_head *head;
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unsigned long flags;
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struct bucket *b;
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tgt_l = container_of(node, struct htab_elem, lru_node);
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b = __select_bucket(htab, tgt_l->hash);
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head = &b->head;
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raw_spin_lock_irqsave(&b->lock, flags);
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hlist_for_each_entry_rcu(l, head, hash_node)
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if (l == tgt_l) {
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hlist_del_rcu(&l->hash_node);
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break;
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}
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raw_spin_unlock_irqrestore(&b->lock, flags);
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return l == tgt_l;
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}
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/* Called from syscall */
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static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
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{
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@ -579,6 +706,70 @@ err:
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return ret;
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}
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static int htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value,
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u64 map_flags)
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{
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struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
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struct htab_elem *l_new, *l_old = NULL;
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struct hlist_head *head;
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unsigned long flags;
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struct bucket *b;
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u32 key_size, hash;
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int ret;
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if (unlikely(map_flags > BPF_EXIST))
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/* unknown flags */
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return -EINVAL;
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WARN_ON_ONCE(!rcu_read_lock_held());
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key_size = map->key_size;
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hash = htab_map_hash(key, key_size);
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b = __select_bucket(htab, hash);
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head = &b->head;
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/* For LRU, we need to alloc before taking bucket's
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* spinlock because getting free nodes from LRU may need
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* to remove older elements from htab and this removal
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* operation will need a bucket lock.
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*/
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l_new = prealloc_lru_pop(htab, key, hash);
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if (!l_new)
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return -ENOMEM;
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memcpy(l_new->key + round_up(map->key_size, 8), value, map->value_size);
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/* bpf_map_update_elem() can be called in_irq() */
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raw_spin_lock_irqsave(&b->lock, flags);
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l_old = lookup_elem_raw(head, hash, key, key_size);
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ret = check_flags(htab, l_old, map_flags);
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if (ret)
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goto err;
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/* add new element to the head of the list, so that
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* concurrent search will find it before old elem
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*/
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hlist_add_head_rcu(&l_new->hash_node, head);
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if (l_old) {
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bpf_lru_node_set_ref(&l_new->lru_node);
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hlist_del_rcu(&l_old->hash_node);
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}
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ret = 0;
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err:
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raw_spin_unlock_irqrestore(&b->lock, flags);
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if (ret)
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bpf_lru_push_free(&htab->lru, &l_new->lru_node);
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else if (l_old)
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bpf_lru_push_free(&htab->lru, &l_old->lru_node);
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return ret;
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}
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static int __htab_percpu_map_update_elem(struct bpf_map *map, void *key,
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void *value, u64 map_flags,
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bool onallcpus)
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@ -671,6 +862,39 @@ static int htab_map_delete_elem(struct bpf_map *map, void *key)
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return ret;
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}
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static int htab_lru_map_delete_elem(struct bpf_map *map, void *key)
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{
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struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
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struct hlist_head *head;
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struct bucket *b;
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struct htab_elem *l;
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unsigned long flags;
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u32 hash, key_size;
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int ret = -ENOENT;
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WARN_ON_ONCE(!rcu_read_lock_held());
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key_size = map->key_size;
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hash = htab_map_hash(key, key_size);
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b = __select_bucket(htab, hash);
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head = &b->head;
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raw_spin_lock_irqsave(&b->lock, flags);
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l = lookup_elem_raw(head, hash, key, key_size);
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if (l) {
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hlist_del_rcu(&l->hash_node);
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ret = 0;
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}
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raw_spin_unlock_irqrestore(&b->lock, flags);
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if (l)
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bpf_lru_push_free(&htab->lru, &l->lru_node);
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return ret;
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}
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static void delete_all_elements(struct bpf_htab *htab)
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{
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int i;
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@ -703,12 +927,11 @@ static void htab_map_free(struct bpf_map *map)
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* not have executed. Wait for them.
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*/
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rcu_barrier();
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if (htab->map.map_flags & BPF_F_NO_PREALLOC) {
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if (htab->map.map_flags & BPF_F_NO_PREALLOC)
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delete_all_elements(htab);
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} else {
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htab_free_elems(htab);
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pcpu_freelist_destroy(&htab->freelist);
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}
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else
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prealloc_destroy(htab);
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free_percpu(htab->extra_elems);
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kvfree(htab->buckets);
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kfree(htab);
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@ -728,6 +951,20 @@ static struct bpf_map_type_list htab_type __read_mostly = {
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.type = BPF_MAP_TYPE_HASH,
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};
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static const struct bpf_map_ops htab_lru_ops = {
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.map_alloc = htab_map_alloc,
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.map_free = htab_map_free,
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.map_get_next_key = htab_map_get_next_key,
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.map_lookup_elem = htab_lru_map_lookup_elem,
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.map_update_elem = htab_lru_map_update_elem,
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.map_delete_elem = htab_lru_map_delete_elem,
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};
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static struct bpf_map_type_list htab_lru_type __read_mostly = {
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.ops = &htab_lru_ops,
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.type = BPF_MAP_TYPE_LRU_HASH,
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};
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/* Called from eBPF program */
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static void *htab_percpu_map_lookup_elem(struct bpf_map *map, void *key)
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{
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@ -798,6 +1035,7 @@ static int __init register_htab_map(void)
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{
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bpf_register_map_type(&htab_type);
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bpf_register_map_type(&htab_percpu_type);
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bpf_register_map_type(&htab_lru_type);
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return 0;
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}
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late_initcall(register_htab_map);
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