[PATCH 0/6] mm/page_owner: add bpf_iter and kfuncs

[Zhen Ni]

Hi all,

Introduction
============

page_owner records who allocated every page and is a core memory-debug
facility, but it currently reaches userspace as the debugfs flat dump:
slicing allocations by pid, comm, NUMA node, cgroup or stack, etc.,
means streaming and parsing the entire file in userspace, which is
expensive on large hosts and hard to query live.

Exposing the same walk to eBPF lets a program filter and aggregate in
the kernel and surface only the records it cares about. This series
adds that access as a seq_file bpf_iter target and an open-coded
iterator.

Implementation
==============

The page walk is factored into page_owner_next_eligible(), shared by
the read path and the iterators so eligibility stays identical. Three
kfuncs expose information that a BPF program cannot decode from the
snapshot alone: the NUMA node, per-page memcg info including the full
cgroup path, and the stack trace behind a stack_depot handle. Each
record is snapshotted under the page_ext RCU lock, so consumers read
a consistent copy.

Testing
=======

The selftest exercises the seq_file and open-coded iterators, and
validates the get_nid, stack_snprint and get_memcg_info kfuncs.

Zhen Ni (6):
  mm/page_owner: extract page_owner_next_eligible() from read loop
  mm/page_owner: add bpf_iter target "page_owner"
  mm/page_owner: add open-coded page_owner iterator
  mm/page_owner: add bpf_page_owner_get_nid() kfunc
  mm/page_owner: add bpf_page_owner_get_memcg_info() kfunc
  selftests/bpf: add tests for the page_owner bpf_iter target

 kernel/bpf/helpers.c                          |   8 +
 mm/Makefile                                   |   3 +
 mm/page_owner.c                               | 219 +++++++++++-------
 mm/page_owner.h                               |  58 +++++
 mm/page_owner_iter.c                          | 180 ++++++++++++++
 .../bpf/prog_tests/page_owner_iter.c          | 173 ++++++++++++++
 .../selftests/bpf/progs/bpf_iter_page_owner.c | 161 +++++++++++++
 7 files changed, 722 insertions(+), 80 deletions(-)
 create mode 100644 mm/page_owner.h
 create mode 100644 mm/page_owner_iter.c
 create mode 100644 tools/testing/selftests/bpf/prog_tests/page_owner_iter.c
 create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_page_owner.c

-- 
2.20.1