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

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Date:   Wed, 2 Nov 2022 18:44:53 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     "Kirill A. Shutemov" <kirill@...temov.name>,
        Matthew Wilcox <willy@...radead.org>,
        David Hildenbrand <david@...hat.com>,
        Vlastimil Babka <vbabka@...e.cz>, Peter Xu <peterx@...hat.com>,
        Yang Shi <shy828301@...il.com>,
        John Hubbard <jhubbard@...dia.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Sidhartha Kumar <sidhartha.kumar@...cle.com>,
        Muchun Song <songmuchun@...edance.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Naoya Horiguchi <naoya.horiguchi@...ux.dev>,
        Mina Almasry <almasrymina@...gle.com>,
        James Houghton <jthoughton@...gle.com>,
        Zach O'Keefe <zokeefe@...gle.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 0/3] mm,huge,rmap: unify and speed up compound mapcounts

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