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: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20210727222335.4029096-1-sdf@google.com

diff --git a/kernel/bpf/local_storage.c b/kernel/bpf/local_storage.c
index 7ed2a14..035e9e3 100644 (file)
--- 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>
@@ -283,9 +284,17 @@ enoent:
 
 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 ||

diff --git a/tools/testing/selftests/bpf/netcnt_common.h b/tools/testing/selftests/bpf/netcnt_common.h
index 81084c1..0ab1c88 100644 (file)
--- a/tools/testing/selftests/bpf/netcnt_common.h
+++ b/tools/testing/selftests/bpf/netcnt_common.h
@@ -6,19 +6,39 @@
 
 #define MAX_PERCPU_PACKETS 32
 
-struct percpu_net_cnt {
-       __u64 packets;
-       __u64 bytes;
+/* 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
 
-       __u64 prev_ts;
+/* Try to estimate kernel's BPF_LOCAL_STORAGE_MAX_VALUE_SIZE: */
+#define BPF_LOCAL_STORAGE_MAX_VALUE_SIZE       (0xFFFF - \
+                                                SIZEOF_BPF_LOCAL_STORAGE_ELEM)
 
-       __u64 prev_packets;
-       __u64 prev_bytes;
+#define PCPU_MIN_UNIT_SIZE                     32768
+
+union percpu_net_cnt {
+       struct {
+               __u64 packets;
+               __u64 bytes;
+
+               __u64 prev_ts;
+
+               __u64 prev_packets;
+               __u64 prev_bytes;
+       };
+       __u8 data[PCPU_MIN_UNIT_SIZE];
 };
 
-struct net_cnt {
-       __u64 packets;
-       __u64 bytes;
+union net_cnt {
+       struct {
+               __u64 packets;
+               __u64 bytes;
+       };
+       __u8 data[BPF_LOCAL_STORAGE_MAX_VALUE_SIZE];
 };
 
 #endif

diff --git a/tools/testing/selftests/bpf/progs/netcnt_prog.c b/tools/testing/selftests/bpf/progs/netcnt_prog.c
index d071adf..43649bc 100644 (file)
--- a/tools/testing/selftests/bpf/progs/netcnt_prog.c
+++ b/tools/testing/selftests/bpf/progs/netcnt_prog.c
@@ -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;
 

diff --git a/tools/testing/selftests/bpf/test_netcnt.c b/tools/testing/selftests/bpf/test_netcnt.c
index a7b9a69..4990a99 100644 (file)
--- a/tools/testing/selftests/bpf/test_netcnt.c
+++ b/tools/testing/selftests/bpf/test_netcnt.c
@@ -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;