[0/3,v2] fs/proc: extend the PAGEMAP_SCAN ioctl to report guard regions

Message

Andrei Vagin March 24, 2025, 6:53 a.m. UTC

Introduce the PAGE_IS_GUARD flag in the PAGEMAP_SCAN ioctl to expose
information about guard regions. This allows userspace tools, such as
CRIU, to detect and handle guard regions.

Currently, CRIU utilizes PAGEMAP_SCAN as a more efficient alternative to
parsing /proc/pid/pagemap. Without this change, guard regions are
incorrectly reported as swap-anon regions, leading CRIU to attempt
dumping them and subsequently failing.

This series should be applied on top of "[PATCH 0/2] fs/proc/task_mmu:
add guard region bit to pagemap":
https://lore.kernel.org/all/2025031926-engraved-footer-3e9b@gregkh/T/

The series includes updates to the documentation and selftests to
reflect the new functionality.

v2:
- sync linux/fs.h with the kernel sources
- address comments from Lorenzo and David.

Andrei Vagin (3):
  fs/proc: extend the PAGEMAP_SCAN ioctl to report guard regions
  tools headers UAPI: Sync linux/fs.h with the kernel sources
  selftests/mm: add PAGEMAP_SCAN guard region test

 Documentation/admin-guide/mm/pagemap.rst   |  1 +
 fs/proc/task_mmu.c                         | 17 ++++---
 include/uapi/linux/fs.h                    |  1 +
 tools/include/uapi/linux/fs.h              | 19 +++++++-
 tools/testing/selftests/mm/guard-regions.c | 57 ++++++++++++++++++++++
 5 files changed, 87 insertions(+), 8 deletions(-)