Commit 33b57e0c authored by Stanislav Fomichev's avatar Stanislav Fomichev Committed by Andrii Nakryiko
Browse files

bpf: Increase supported cgroup storage value size 



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
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).

v4:
* remove inner union (Andrii Nakryiko)
* keep net_cnt on the stack (Andrii Nakryiko)

v3:
* refine SIZEOF_BPF_LOCAL_STORAGE_ELEM comment (Yonghong Song)
* anonymous struct in percpu_net_cnt & net_cnt (Yonghong Song)
* reorder free (Yonghong Song)

v2:
* cap max_value_size instead of BUILD_BUG_ON (Martin KaFai Lau)

Signed-off-by: default avatarStanislav Fomichev <sdf@google.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20210727222335.4029096-1-sdf@google.com
parent 043c5bb3

kernel/bpf/local_storage.c

+10 −1
Original line number Diff line number Diff line 
//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>
@@ -283,9 +284,17 @@ static int cgroup_storage_get_next_key(struct bpf_map *_map, void *key, 


static struct bpf_map *cgroup_storage_map_alloc(union bpf_attr *attr)

{

	__u32 max_value_size = BPF_LOCAL_STORAGE_MAX_VALUE_SIZE;

	int numa_node = bpf_map_attr_numa_node(attr);

	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_PERCPU_CGROUP_STORAGE)

		max_value_size = min_t(__u32, max_value_size,

				       PCPU_MIN_UNIT_SIZE);



	if (attr->key_size != sizeof(struct bpf_cgroup_storage_key) &&

	    attr->key_size != sizeof(__u64))

		return ERR_PTR(-EINVAL);
@@ -293,7 +302,7 @@ static struct bpf_map *cgroup_storage_map_alloc(union bpf_attr *attr) 
	if (attr->value_size == 0)

		return ERR_PTR(-EINVAL);



	if (attr->value_size > PAGE_SIZE)

	if (attr->value_size > max_value_size)

		return ERR_PTR(-E2BIG);



	if (attr->map_flags & ~LOCAL_STORAGE_CREATE_FLAG_MASK ||

tools/testing/selftests/bpf/netcnt_common.h

+29 −9
Original line number Diff line number Diff line
@@ -6,7 +6,22 @@ 


#define MAX_PERCPU_PACKETS 32



struct percpu_net_cnt {

/* sizeof(struct bpf_local_storage_elem):

 *

 * It really is about 128 bytes on x86_64, but allocate more to account for

 * possible layout changes, different architectures, etc.

 * The kernel will wrap up to PAGE_SIZE internally anyway.

 */

#define SIZEOF_BPF_LOCAL_STORAGE_ELEM		256



/* Try to estimate kernel's BPF_LOCAL_STORAGE_MAX_VALUE_SIZE: */

#define BPF_LOCAL_STORAGE_MAX_VALUE_SIZE	(0xFFFF - \

						 SIZEOF_BPF_LOCAL_STORAGE_ELEM)



#define PCPU_MIN_UNIT_SIZE			32768



union percpu_net_cnt {

	struct {

		__u64 packets;

		__u64 bytes;
@@ -15,10 +30,15 @@ struct percpu_net_cnt { 
		__u64 prev_packets;

		__u64 prev_bytes;

	};

	__u8 data[PCPU_MIN_UNIT_SIZE];

};



struct net_cnt {

union net_cnt {

	struct {

		__u64 packets;

		__u64 bytes;

	};

	__u8 data[BPF_LOCAL_STORAGE_MAX_VALUE_SIZE];

};



#endif

tools/testing/selftests/bpf/progs/netcnt_prog.c

+4 −4
Original line number Diff line number Diff line
@@ -13,21 +13,21 @@ 
struct {

	__uint(type, BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE);

	__type(key, struct bpf_cgroup_storage_key);

	__type(value, struct percpu_net_cnt);

	__type(value, union percpu_net_cnt);

} percpu_netcnt SEC(".maps");



struct {

	__uint(type, BPF_MAP_TYPE_CGROUP_STORAGE);

	__type(key, struct bpf_cgroup_storage_key);

	__type(value, struct net_cnt);

	__type(value, union net_cnt);

} netcnt SEC(".maps");



SEC("cgroup/skb")

int bpf_nextcnt(struct __sk_buff *skb)

{

	struct percpu_net_cnt *percpu_cnt;

	union percpu_net_cnt *percpu_cnt;

	char fmt[] = "%d %llu %llu\n";

	struct net_cnt *cnt;

	union net_cnt *cnt;

	__u64 ts, dt;

	int ret;

tools/testing/selftests/bpf/test_netcnt.c

+2 −2
Original line number Diff line number Diff line
@@ -33,14 +33,14 @@ static int bpf_find_map(const char *test, struct bpf_object *obj, 


int main(int argc, char **argv)

{

	struct percpu_net_cnt *percpu_netcnt;

	union percpu_net_cnt *percpu_netcnt;

	struct bpf_cgroup_storage_key key;

	int map_fd, percpu_map_fd;

	int error = EXIT_FAILURE;

	struct net_cnt netcnt;

	struct bpf_object *obj;

	int prog_fd, cgroup_fd;

	unsigned long packets;

	union net_cnt netcnt;

	unsigned long bytes;

	int cpu, nproc;

	__u32 prog_cnt;