From: Alexei Starovoitov <ast@xxxxxxxxxx>
Convert dynamic allocations in percpu hash map from alloc_percpu() to
bpf_mem_cache_alloc() from per-cpu bpf_mem_alloc. Since bpf_mem_alloc frees
objects after RCU gp the call_rcu() is removed. pcpu_init_value() now needs to
zero-fill per-cpu allocations, since dynamically allocated map elements are now
similar to full prealloc, since alloc_percpu() is not called inline and the
elements are reused in the freelist.
Acked-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
---
kernel/bpf/hashtab.c | 45 +++++++++++++++++++-------------------------
1 file changed, 19 insertions(+), 26 deletions(-)
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 70b02ff4445e..a77b9c4a4e48 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -94,6 +94,7 @@ struct bucket {
struct bpf_htab {
struct bpf_map map;
struct bpf_mem_alloc ma;
+ struct bpf_mem_alloc pcpu_ma;
struct bucket *buckets;
void *elems;
union {
@@ -121,14 +122,14 @@ struct htab_elem {
struct {
void *padding;
union {
- struct bpf_htab *htab;
struct pcpu_freelist_node fnode;
struct htab_elem *batch_flink;
};
};
};
union {
- struct rcu_head rcu;
+ /* pointer to per-cpu pointer */
+ void *ptr_to_pptr;
struct bpf_lru_node lru_node;
};
u32 hash;
@@ -448,8 +449,6 @@ static int htab_map_alloc_check(union bpf_attr *attr)
bool zero_seed = (attr->map_flags & BPF_F_ZERO_SEED);
int numa_node = bpf_map_attr_numa_node(attr);
- BUILD_BUG_ON(offsetof(struct htab_elem, htab) !=
- offsetof(struct htab_elem, hash_node.pprev));
BUILD_BUG_ON(offsetof(struct htab_elem, fnode.next) !=
offsetof(struct htab_elem, hash_node.pprev));
@@ -610,6 +609,12 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
err = bpf_mem_alloc_init(&htab->ma, htab->elem_size, false);
if (err)
goto free_map_locked;
+ if (percpu) {
+ err = bpf_mem_alloc_init(&htab->pcpu_ma,
+ round_up(htab->map.value_size, 8), true);
+ if (err)
+ goto free_map_locked;
+ }
}
return &htab->map;
@@ -620,6 +625,7 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
for (i = 0; i < HASHTAB_MAP_LOCK_COUNT; i++)
free_percpu(htab->map_locked[i]);
bpf_map_area_free(htab->buckets);
+ bpf_mem_alloc_destroy(&htab->pcpu_ma);
bpf_mem_alloc_destroy(&htab->ma);
free_htab:
lockdep_unregister_key(&htab->lockdep_key);
@@ -895,19 +901,11 @@ static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
static void htab_elem_free(struct bpf_htab *htab, struct htab_elem *l)
{
if (htab->map.map_type == BPF_MAP_TYPE_PERCPU_HASH)
- free_percpu(htab_elem_get_ptr(l, htab->map.key_size));
+ bpf_mem_cache_free(&htab->pcpu_ma, l->ptr_to_pptr);
check_and_free_fields(htab, l);
bpf_mem_cache_free(&htab->ma, l);
}
-static void htab_elem_free_rcu(struct rcu_head *head)
-{
- struct htab_elem *l = container_of(head, struct htab_elem, rcu);
- struct bpf_htab *htab = l->htab;
-
- htab_elem_free(htab, l);
-}
-
static void htab_put_fd_value(struct bpf_htab *htab, struct htab_elem *l)
{
struct bpf_map *map = &htab->map;
@@ -953,12 +951,7 @@ static void free_htab_elem(struct bpf_htab *htab, struct htab_elem *l)
__pcpu_freelist_push(&htab->freelist, &l->fnode);
} else {
dec_elem_count(htab);
- if (htab->map.map_type == BPF_MAP_TYPE_PERCPU_HASH) {
- l->htab = htab;
- call_rcu(&l->rcu, htab_elem_free_rcu);
- } else {
- htab_elem_free(htab, l);
- }
+ htab_elem_free(htab, l);
}
}
@@ -983,13 +976,12 @@ static void pcpu_copy_value(struct bpf_htab *htab, void __percpu *pptr,
static void pcpu_init_value(struct bpf_htab *htab, void __percpu *pptr,
void *value, bool onallcpus)
{
- /* When using prealloc and not setting the initial value on all cpus,
- * zero-fill element values for other cpus (just as what happens when
- * not using prealloc). Otherwise, bpf program has no way to ensure
+ /* When not setting the initial value on all cpus, zero-fill element
+ * values for other cpus. Otherwise, bpf program has no way to ensure
* known initial values for cpus other than current one
* (onallcpus=false always when coming from bpf prog).
*/
- if (htab_is_prealloc(htab) && !onallcpus) {
+ if (!onallcpus) {
u32 size = round_up(htab->map.value_size, 8);
int current_cpu = raw_smp_processor_id();
int cpu;
@@ -1060,18 +1052,18 @@ static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
memcpy(l_new->key, key, key_size);
if (percpu) {
- size = round_up(size, 8);
if (prealloc) {
pptr = htab_elem_get_ptr(l_new, key_size);
} else {
/* alloc_percpu zero-fills */
- pptr = bpf_map_alloc_percpu(&htab->map, size, 8,
- GFP_NOWAIT | __GFP_NOWARN);
+ pptr = bpf_mem_cache_alloc(&htab->pcpu_ma);
if (!pptr) {
bpf_mem_cache_free(&htab->ma, l_new);
l_new = ERR_PTR(-ENOMEM);
goto dec_count;
}
+ l_new->ptr_to_pptr = pptr;
+ pptr = *(void **)pptr;
}
pcpu_init_value(htab, pptr, value, onallcpus);
@@ -1568,6 +1560,7 @@ static void htab_map_free(struct bpf_map *map)
bpf_map_free_kptr_off_tab(map);
free_percpu(htab->extra_elems);
bpf_map_area_free(htab->buckets);
+ bpf_mem_alloc_destroy(&htab->pcpu_ma);
bpf_mem_alloc_destroy(&htab->ma);
if (htab->use_percpu_counter)
percpu_counter_destroy(&htab->pcount);
--
2.30.2
