[RFC v3 0/4] move PG_slab flag to page_type

[Hyeonggon Yoo <42.hyeyoo@gmail.com>]

RFC v2:
https://lore.kernel.org/linux-mm/20221106140355.294845-1-42.hyeyoo@gmail.com/

This patch series moves PG_slab page flag to page_type,
freeing one bit in page->flags and introduces %pGt format
that prints human-readable page_type like %pGp for printing page flags.

See changelog of patch 2 for more implementation details.

Thanks everyone that gave valuable comments.

v2 -> v3:
- dropped show_page_types() in a thought that it is not interesting
  to track refcount of non-usermapped pages.
- added patch 1 that cleans up MF_MSG_SLAB in hwpoison
- split implementation and application of %pGt to separate patches.
- instead of printing "no page_type for ..." in %pGt, just print 
  '0x<value>()' for a page that does not use page_type field.

Hyeonggon Yoo (4):
  mm/hwpoison: remove MF_MSG_SLAB from action_page_types
  mm: move PG_slab flag to page_type
  mm, printk: introduce new format %pGt for page_type
  mm/debug: use %pGt to print page_type in dump_page()

 Documentation/core-api/printk-formats.rst |  3 +-
 fs/proc/page.c                            | 13 ++--
 include/linux/mm_types.h                  | 11 ++--
 include/linux/page-flags.h                | 77 ++++++++++++++++-------
 include/trace/events/mmflags.h            |  8 ++-
 kernel/crash_core.c                       |  3 +-
 lib/test_printf.c                         | 26 ++++++++
 lib/vsprintf.c                            | 21 +++++++
 mm/debug.c                                |  7 +++
 mm/internal.h                             |  1 +
 mm/memory-failure.c                       | 10 ---
 mm/slab.c                                 | 44 ++++++++-----
 mm/slab.h                                 |  3 +-
 13 files changed, 162 insertions(+), 65 deletions(-)

-- 
2.32.0