[0/3] mm,huge,rmap: unify and speed up compound mapcounts

Message

Hugh Dickins Nov. 3, 2022, 1:44 a.m. UTC

I had intended to send just a self-explanatory 1/2 and 2/2 against
6.1-rc3 on Monday; but checked for clashes with linux-next (mainly
mm-unstable) just before sending, and fuzz in mm_types.h revealed
not just a clash with Sidhartha's series, but also that I had missed
the hugetlb usage of tail page->private, problematic for me on 32-bit.

So that series was slightly broken; and although it would probably
have been easy to fix with a "SUBPAGE_INDEX_SUBPOOL = 2" patch,
that would not have moved us forward very well.  So this series is
against next-20221102 (and hopefully later nexts), with a preparatory
1/3 to rejig the hugetlb tail private usage, on top of Sidhartha's.

1/3 mm,hugetlb: use folio fields in second tail page
2/3 mm,thp,rmap: simplify compound page mapcount handling
3/3 mm,thp,rmap: lock_compound_mapcounts() on THP mapcounts

2/3 and 3/3 can almost be applied cleanly to 6.1-rc3 (okay when
you are on 64-bit): just a couple of easily resolved rejects.

 Documentation/mm/transhuge.rst |  34 +---
 include/linux/hugetlb.h        |  23 +--
 include/linux/hugetlb_cgroup.h |  31 +--
 include/linux/mm.h             |  85 ++++++---
 include/linux/mm_types.h       |  91 ++++++---
 include/linux/page-flags.h     |  21 --
 include/linux/rmap.h           |  12 +-
 mm/Kconfig                     |   2 +-
 mm/debug.c                     |   5 +-
 mm/folio-compat.c              |   6 -
 mm/huge_memory.c               |  37 +---
 mm/hugetlb.c                   |   2 +
 mm/khugepaged.c                |  11 +-
 mm/memory-failure.c            |   5 +-
 mm/page_alloc.c                |  27 +--
 mm/rmap.c                      | 359 ++++++++++++++++++++---------------
 mm/util.c                      |  79 --------
 17 files changed, 401 insertions(+), 429 deletions(-)

Hugh