[PATCH bpf-next v2 0/6] bpf: Implement cgroup local storage available to non-cgroup-attached bpf progs

Yonghong Song
2022-10-20T22:13:06Z

There already exists a local storage implementation for cgroup-attached
bpf programs. See map type BPF_MAP_TYPE_CGROUP_STORAGE and helper
bpf_get_local_storage(). But there are use cases such that non-cgroup
attached bpf progs wants to access cgroup local storage data. For example,
tc egress prog has access to sk and cgroup. It is possible to use
sk local storage to emulate cgroup local storage by storing data in socket.
But this is a waste as it could be lots of sockets belonging to a particular
cgroup. Alternatively, a separate map can be created with cgroup id as the key.
But this will introduce additional overhead to manipulate the new map.
A cgroup local storage, similar to existing sk/inode/task storage,
should help for this use case.

This patch implemented new cgroup local storage available to
non-cgroup-attached bpf programs. In the patch series, Patch 1
is a preparation patch. Patch 2 implemented new cgroup local storage
kernel support. Patches 3 and 4 implemented libbpf and bpftool support.
Patch 5 added two tests to validate kernel/libbpf implementations.
Patch 6 added documentation for new BPF_MAP_TYPE_CGRP_STORAGE map type
and comparison of the old and new cgroup local storage maps.

Changelogs:
v1 -> v2:
. change map name from BPF_MAP_TYPE_CGROUP_LOCAL_STORAGE to
BPF_MAP_TYPE_CGRP_STORAGE.
. removed support of sleepable programs.
. changed the place of freeing cgrp local storage from put_css_set_locked()
to css_free_rwork_fn().
. added map documentation.

Yonghong Song (6):
bpf: Make struct cgroup btf id global
bpf: Implement cgroup storage available to non-cgroup-attached bpf
progs
libbpf: Support new cgroup local storage
bpftool: Support new cgroup local storage
selftests/bpf: Add selftests for cgroup local storage
docs/bpf: Add documentation for map type BPF_MAP_TYPE_CGRP_STROAGE

Documentation/bpf/map_cgrp_storage.rst | 104 +++++++
include/linux/bpf.h | 3 +
include/linux/bpf_types.h | 1 +
include/linux/btf_ids.h | 1 +
include/linux/cgroup-defs.h | 4 +
include/uapi/linux/bpf.h | 48 ++-
kernel/bpf/Makefile | 2 +-
kernel/bpf/bpf_cgrp_storage.c | 276 ++++++++++++++++++
kernel/bpf/cgroup_iter.c | 2 +-
kernel/bpf/helpers.c | 6 +
kernel/bpf/syscall.c | 3 +-
kernel/bpf/verifier.c | 13 +-
kernel/cgroup/cgroup.c | 4 +
kernel/trace/bpf_trace.c | 4 +
scripts/bpf_doc.py | 2 +
.../bpf/bpftool/Documentation/bpftool-map.rst | 2 +-
tools/bpf/bpftool/map.c | 2 +-
tools/include/uapi/linux/bpf.h | 48 ++-
tools/lib/bpf/libbpf.c | 1 +
tools/lib/bpf/libbpf_probes.c | 1 +
.../bpf/prog_tests/cgroup_local_storage.c | 92 ++++++
.../bpf/progs/cgroup_local_storage.c | 88 ++++++
.../selftests/bpf/progs/cgroup_ls_recursion.c | 70 +++++
23 files changed, 769 insertions(+), 8 deletions(-)
create mode 100644 Documentation/bpf/map_cgrp_storage.rst
create mode 100644 kernel/bpf/bpf_cgrp_storage.c
create mode 100644 tools/testing/selftests/bpf/prog_tests/cgroup_local_storage.c
create mode 100644 tools/testing/selftests/bpf/progs/cgroup_local_storage.c
create mode 100644 tools/testing/selftests/bpf/progs/cgroup_ls_recursion.c

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2.30.2