The patch titled
Subject: mm/rmap: move folio_test_anon() check out of __folio_set_anon()
has been added to the -mm mm-unstable branch. Its filename is
mm-rmap-move-folio_test_anon-check-out-of-__folio_set_anon.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-rmap-move-folio_test_anon-check-out-of-__folio_set_anon.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: David Hildenbrand <david@xxxxxxxxxx>
Subject: mm/rmap: move folio_test_anon() check out of __folio_set_anon()
Date: Wed, 13 Sep 2023 14:51:10 +0200
Let's handle it in the caller; no need for the "first" check based on the
mapcount.
We really only end up with !anon pages in page_add_anon_rmap() via
do_swap_page(), where we hold the folio lock. So races are not possible.
Add a VM_WARN_ON_FOLIO() to make sure that we really hold the folio lock.
In the future, we might want to let do_swap_page() use
folio_add_new_anon_rmap() on new pages instead: however, we might have to
pass then whether the folio is exclusive or not. So keep it in there for
now.
For hugetlb we never expect to have a non-anon page in
hugepage_add_anon_rmap(). Remove that code, along with some other checks
that are either not required or were checked in
hugepage_add_new_anon_rmap() already.
Link: https://lkml.kernel.org/r/20230913125113.313322-4-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/rmap.c | 23 ++++++++---------------
1 file changed, 8 insertions(+), 15 deletions(-)
--- a/mm/rmap.c~mm-rmap-move-folio_test_anon-check-out-of-__folio_set_anon
+++ a/mm/rmap.c
@@ -1135,9 +1135,6 @@ static void __folio_set_anon(struct foli
BUG_ON(!anon_vma);
- if (folio_test_anon(folio))
- return;
-
/*
* If the folio isn't exclusive to this vma, we must use the _oldest_
* possible anon_vma for the folio mapping!
@@ -1239,12 +1236,12 @@ void page_add_anon_rmap(struct page *pag
if (nr)
__lruvec_stat_mod_folio(folio, NR_ANON_MAPPED, nr);
- if (likely(!folio_test_ksm(folio))) {
- if (first)
- __folio_set_anon(folio, vma, address,
- !!(flags & RMAP_EXCLUSIVE));
- else
- __page_check_anon_rmap(folio, page, vma, address);
+ if (unlikely(!folio_test_anon(folio))) {
+ VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio);
+ __folio_set_anon(folio, vma, address,
+ !!(flags & RMAP_EXCLUSIVE));
+ } else if (likely(!folio_test_ksm(folio))) {
+ __page_check_anon_rmap(folio, page, vma, address);
}
if (flags & RMAP_EXCLUSIVE)
SetPageAnonExclusive(page);
@@ -2528,17 +2525,13 @@ void hugepage_add_anon_rmap(struct page
unsigned long address, rmap_t flags)
{
struct folio *folio = page_folio(page);
- struct anon_vma *anon_vma = vma->anon_vma;
int first;
- BUG_ON(!folio_test_locked(folio));
- BUG_ON(!anon_vma);
+ VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
+
first = atomic_inc_and_test(&folio->_entire_mapcount);
VM_BUG_ON_PAGE(!first && (flags & RMAP_EXCLUSIVE), page);
VM_BUG_ON_PAGE(!first && PageAnonExclusive(page), page);
- if (first)
- __folio_set_anon(folio, vma, address,
- !!(flags & RMAP_EXCLUSIVE));
if (flags & RMAP_EXCLUSIVE)
SetPageAnonExclusive(page);
}
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
mm-rmap-drop-stale-comment-in-page_add_anon_rmap-and-hugepage_add_anon_rmap.patch
mm-rmap-move-setpageanonexclusive-out-of-__page_set_anon_rmap.patch
mm-rmap-move-folio_test_anon-check-out-of-__folio_set_anon.patch
mm-rmap-warn-on-new-pte-mapped-folios-in-page_add_anon_rmap.patch
mm-rmap-simplify-pageanonexclusive-sanity-checks-when-adding-anon-rmap.patch
mm-rmap-pass-folio-to-hugepage_add_anon_rmap.patch
