+ mm-mm_init-initialize-page-_mapcount-directly-in-__init_single_page.patch added to mm-unstable branch

+ mm-mm_init-initialize-page-_mapcount-directly-in-__init_single_page.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/mm_init: initialize page->_mapcount directly in __init_single_page()
has been added to the -mm mm-unstable branch.  Its filename is
     mm-mm_init-initialize-page-_mapcount-directly-in-__init_single_page.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mm_init-initialize-page-_mapcount-directly-in-__init_single_page.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days

------------------------------------------------------
From: David Hildenbrand <david@redhat.com>
Subject: mm/mm_init: initialize page->_mapcount directly in __init_single_page()
Date: Wed, 29 May 2024 13:19:04 +0200

Let's simply reinitialize the page->_mapcount directly.  We can now get
rid of page_mapcount_reset().

Link: https://lkml.kernel.org/r/20240529111904.2069608-7-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/mm.h |    5 -----
 mm/mm_init.c       |    2 +-
 2 files changed, 1 insertion(+), 6 deletions(-)

--- a/include/linux/mm.h~mm-mm_init-initialize-page-_mapcount-directly-in-__init_single_page
+++ a/include/linux/mm.h
@@ -1206,11 +1206,6 @@ static inline int folio_entire_mapcount(
 	return atomic_read(&folio->_entire_mapcount) + 1;
 }
 
-static inline void page_mapcount_reset(struct page *page)
-{
-	atomic_set(&(page)->_mapcount, -1);
-}
-
 /**
  * page_mapcount() - Number of times this precise page is mapped.
  * @page: The page.
--- a/mm/mm_init.c~mm-mm_init-initialize-page-_mapcount-directly-in-__init_single_page
+++ a/mm/mm_init.c
@@ -568,7 +568,7 @@ void __meminit __init_single_page(struct
 	mm_zero_struct_page(page);
 	set_page_links(page, zone, nid, pfn);
 	init_page_count(page);
-	page_mapcount_reset(page);
+	atomic_set(&page->_mapcount, -1);
 	page_cpupid_reset_last(page);
 	page_kasan_tag_reset(page);
 
_

Patches currently in -mm which might be from david@redhat.com are

mm-memory-move-page_count-check-into-validate_page_before_insert.patch
mm-memory-cleanly-support-zeropage-in-vm_insert_page-vm_map_pages-and-vmf_insert_mixed.patch
mm-rmap-sanity-check-that-zeropages-are-not-passed-to-rmap.patch
mm-update-_mapcount-and-page_type-documentation.patch
mm-allow-reuse-of-the-lower-16-bit-of-the-page-type-with-an-actual-type.patch
mm-zsmalloc-use-a-proper-page-type.patch
mm-page_alloc-clear-pagebuddy-using-__clearpagebuddy-for-bad-pages.patch
mm-filemap-reinitialize-folio-_mapcount-directly.patch
mm-mm_init-initialize-page-_mapcount-directly-in-__init_single_page.patch