Re: [PATCH bpf-next v2 00/13] bpf: Add support for local percpu kptr

[Yonghong Song <yonghong.song@linux.dev>]

On 8/25/23 12:53 PM, Yonghong Song wrote:
> Patch set [1] implemented cgroup local storage BPF_MAP_TYPE_CGRP_STORAGE
> similar to sk/task/inode local storage and old BPF_MAP_TYPE_CGROUP_STORAGE
> map is marked as deprecated since old BPF_MAP_TYPE_CGROUP_STORAGE map can
> only work with current cgroup.
> 
> Similarly, the existing BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE map
> is a percpu version of BPF_MAP_TYPE_CGROUP_STORAGE and only works
> with current cgroup. But there is no replacement which can work
> with arbitrary cgroup.
> 
> This patch set solved this problem but adding support for local
> percpu kptr. The map value can have a percpu kptr field which holds
> a bpf prog allocated percpu data. The below is an example,
> 
>    struct percpu_val_t {
>      ... fields ...
>    }
> 
>    struct map_value_t {
>      struct percpu_val_t __percpu *percpu_data_ptr;
>    }
> 
> In the above, 'map_value_t' is the map value type for a
> BPF_MAP_TYPE_CGRP_STORAGE map. User can access 'percpu_data_ptr'
> and then read/write percpu data. This covers BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE
> and more. So BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE map type
> is marked as deprecated.
> 
> In additional, local percpu kptr supports the same map type
> as other kptrs including hash, lru_hash, array, sk/inode/task/cgrp
> local storage. Currently, percpu data structure does not support
> non-scalars or special fields (e.g., bpf_spin_lock, bpf_rb_root, etc.).
> They can be supported in the future if there exist use cases.
> 
> Please for individual patches for details.
> 
>    [1] https://lore.kernel.org/all/20221026042835.672317-1-yhs@fb.com/
> 
> Changelog:
>    v1 -> v2:
>      - does not support special fields in percpu data structure.
>      - rename __percpu attr to __percpu_kptr attr.
>      - rename BPF_KPTR_PERCPU_REF to BPF_KPTR_PERCPU.
>      - better code to handle bpf_{this,per}_cpu_ptr() helpers.
>      - add more negative tests.
>      - fix a bpftool related test failure.
> 
> Yonghong Song (13):
>    bpf: Add support for non-fix-size percpu mem allocation
>    bpf: Add BPF_KPTR_PERCPU as a field type
>    bpf: Add alloc/xchg/direct_access support for local percpu kptr
>    bpf: Add bpf_this_cpu_ptr/bpf_per_cpu_ptr support for allocated percpu
>      obj
>    selftests/bpf: Update error message in negative linked_list test
>    libbpf: Add __percpu_kptr macro definition
>    selftests/bpf: Add bpf_percpu_obj_{new,drop}() macro in
>      bpf_experimental.h
>    selftests/bpf: Add tests for array map with local percpu kptr
>    bpf: Mark OBJ_RELEASE argument as MEM_RCU when possible
>    selftests/bpf: Remove unnecessary direct read of local percpu kptr
>    selftests/bpf: Add tests for cgrp_local_storage with local percpu kptr
>    selftests/bpf: Add some negative tests
>    bpf: Mark BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE deprecated
> 
>   include/linux/bpf.h                           |  22 +-
>   include/linux/bpf_verifier.h                  |   1 +
>   include/uapi/linux/bpf.h                      |   9 +-
>   kernel/bpf/btf.c                              |   5 +
>   kernel/bpf/core.c                             |   8 +-
>   kernel/bpf/helpers.c                          |  16 ++
>   kernel/bpf/memalloc.c                         |  14 +-
>   kernel/bpf/syscall.c                          |   4 +
>   kernel/bpf/verifier.c                         | 191 +++++++++++++++---
>   tools/include/uapi/linux/bpf.h                |   9 +-
>   tools/lib/bpf/bpf_helpers.h                   |   1 +
>   .../testing/selftests/bpf/bpf_experimental.h  |  31 +++
>   .../selftests/bpf/prog_tests/linked_list.c    |   4 +-
>   .../selftests/bpf/prog_tests/percpu_alloc.c   | 125 ++++++++++++
>   .../selftests/bpf/progs/percpu_alloc_array.c  | 183 +++++++++++++++++
>   .../progs/percpu_alloc_cgrp_local_storage.c   | 105 ++++++++++
>   .../selftests/bpf/progs/percpu_alloc_fail.c   | 164 +++++++++++++++
>   .../selftests/bpf/test_bpftool_synctypes.py   |   9 +
>   18 files changed, 848 insertions(+), 53 deletions(-)
>   create mode 100644 tools/testing/selftests/bpf/prog_tests/percpu_alloc.c
>   create mode 100644 tools/testing/selftests/bpf/progs/percpu_alloc_array.c
>   create mode 100644 tools/testing/selftests/bpf/progs/percpu_alloc_cgrp_local_storage.c
>   create mode 100644 tools/testing/selftests/bpf/progs/percpu_alloc_fail.c

There is a test failure for libbpf_str/bpf_map_type_str reported by CI,
I will fix it in the next revision.