bpf: Check map->record at the beginning of check_and_free_fields()

When there are no special fields in the map value, there is no need to
invoke bpf_obj_free_fields(). Therefore, checking the validity of
map->record in advance.

After the change, the benchmark result of the per-cpu update case in
map_perf_test increased by 40% under a 16-CPU VM.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20250315150930.1511727-1-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index c308300fc72f671acb066e854a92ab138dcf4fa4..877298133fdae792772b51a780905a97dcd480a4 100644 (file)
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -787,6 +787,9 @@ static int htab_lru_map_gen_lookup(struct bpf_map *map,
 static void check_and_free_fields(struct bpf_htab *htab,
                                  struct htab_elem *elem)
 {
+       if (IS_ERR_OR_NULL(htab->map.record))
+               return;
+
        if (htab_is_percpu(htab)) {
                void __percpu *pptr = htab_elem_get_ptr(elem, htab->map.key_size);
                int cpu;