On 07/23, Martin KaFai Lau wrote:

On Thu, Jul 22, 2021 at 05:27:47PM -0700, Stanislav Fomichev wrote:

quoted

Current max cgroup storage value size is 4k (PAGE_SIZE). The other local
storages accept up to 64k (BPF_LOCAL_STORAGE_MAX_VALUE_SIZE). Let's  

align

quoted

max cgroup value size with the other storages.

For percpu, the max is 32k (PCPU_MIN_UNIT_SIZE) because percpu
allocator is not happy about larger values.

netcnt test is extended to exercise those maximum values
(non-percpu max size is close to, but not real max).

Signed-off-by: Stanislav Fomichev <redacted>
---
 kernel/bpf/local_storage.c                    | 12 +++++-
 tools/testing/selftests/bpf/netcnt_common.h   | 38 +++++++++++++++----
 .../testing/selftests/bpf/progs/netcnt_prog.c | 29 +++++++-------
 tools/testing/selftests/bpf/test_netcnt.c     | 25 +++++++-----
 4 files changed, 73 insertions(+), 31 deletions(-)

diff --git a/kernel/bpf/local_storage.c b/kernel/bpf/local_storage.c
index 7ed2a14dc0de..a276da74c20a 100644
--- a/kernel/bpf/local_storage.c
+++ b/kernel/bpf/local_storage.c

@@ -1,6 +1,7 @@
 //SPDX-License-Identifier: GPL-2.0
 #include <linux/bpf-cgroup.h>
 #include <linux/bpf.h>
+#include <linux/bpf_local_storage.h>
 #include <linux/btf.h>
 #include <linux/bug.h>
 #include <linux/filter.h>

@@ -284,8 +285,17 @@ static int cgroup_storage_get_next_key(struct  

bpf_map *_map, void *key,

quoted

 static struct bpf_map *cgroup_storage_map_alloc(union bpf_attr *attr)
 {
 	int numa_node = bpf_map_attr_numa_node(attr);
+	__u32 max_value_size = PCPU_MIN_UNIT_SIZE;
 	struct bpf_cgroup_storage_map *map;

+	/* percpu is bound by PCPU_MIN_UNIT_SIZE, non-percu
+	 * is the same as other local storages.
+	 */
+	if (attr->map_type == BPF_MAP_TYPE_CGROUP_STORAGE)
+		max_value_size = BPF_LOCAL_STORAGE_MAX_VALUE_SIZE;
+
+	BUILD_BUG_ON(PCPU_MIN_UNIT_SIZE > BPF_LOCAL_STORAGE_MAX_VALUE_SIZE);

If PCPU_MIN_UNIT_SIZE did become larger, I assume it would be bounded by
BPF_LOCAL_STORAGE_MAX_VALUE_SIZE again?

Instead of BUILD_BUG_ON, how about a min_t here:

	if (attr->map_type == BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE)
		max_value_size = min_t(__u32,
					BPF_LOCAL_STORAGE_MAX_VALUE_SIZE,
					PCPU_MIN_UNIT_SIZE);

Sounds like a much better idea, thanks, will incorporate into v2.