linux-kernel - [PATCH v1 0/6] fs/proc: move page_mapcount() to fs/proc/internal.h

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Date: Fri,  7 Jun 2024 14:23:51 +0200
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org,
	linux-doc@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	David Hildenbrand <david@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jonathan Corbet <corbet@....net>
Subject: [PATCH v1 0/6] fs/proc: move page_mapcount() to fs/proc/internal.h

With all other page_mapcount() users in the tree gone, move
page_mapcount() to fs/proc/internal.h, rename it and extend the
documentation to prevent future (ab)use.

... of course, I find some issues while working on that code that I sort
first ;)

We'll now only end up calling page_mapcount()
[now folio_precise_page_mapcount()] on pages mapped via present page table
entries. Except for /proc/kpagecount, that still does questionable things,
but we'll leave that legacy interface as is for now.

Did a quick sanity check. Likely we would want some better selfestest
for /proc/$/pagemap + smaps. I'll see if I can find some time to write
some more.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Jonathan Corbet <corbet@....net>

David Hildenbrand (6):
  fs/proc/task_mmu: indicate PM_FILE for PMD-mapped file THP
  fs/proc/task_mmu: don't indicate PM_MMAP_EXCLUSIVE without PM_PRESENT
  fs/proc/task_mmu: properly detect PM_MMAP_EXCLUSIVE per page of
    PMD-mapped THPs
  fs/proc/task_mmu: account non-present entries as "maybe shared, but no
    idea how often"
  fs/proc: move page_mapcount() to fs/proc/internal.h
  Documentation/admin-guide/mm/pagemap.rst: drop "Using pagemap to do
    something useful"

 Documentation/admin-guide/mm/pagemap.rst |  21 -----
 fs/proc/internal.h                       |  33 ++++++++
 fs/proc/page.c                           |  21 +++--
 fs/proc/task_mmu.c                       | 102 +++++++++++++----------
 include/linux/mm.h                       |  27 +-----
 5 files changed, 104 insertions(+), 100 deletions(-)

base-commit: 19b8422c5bd56fb5e7085995801c6543a98bda1f
-- 
2.45.2