The patch titled
Subject: mm/rmap: simplify PageAnonExclusive sanity checks when adding anon rmap
has been added to the -mm mm-unstable branch. Its filename is
mm-rmap-simplify-pageanonexclusive-sanity-checks-when-adding-anon-rmap.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-rmap-simplify-pageanonexclusive-sanity-checks-when-adding-anon-rmap.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: simplify PageAnonExclusive sanity checks when adding anon rmap
Date: Wed, 13 Sep 2023 14:51:12 +0200
Let's sanity-check PageAnonExclusive vs. mapcount in page_add_anon_rmap()
and hugepage_add_anon_rmap() after setting PageAnonExclusive simply by
re-reading the mapcounts.
We can stop initializing the "first" variable in page_add_anon_rmap() and
no longer need an atomic_inc_and_test() in hugepage_add_anon_rmap().
While at it, switch to VM_WARN_ON_FOLIO().
Link: https://lkml.kernel.org/r/20230913125113.313322-6-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 | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
--- a/mm/rmap.c~mm-rmap-simplify-pageanonexclusive-sanity-checks-when-adding-anon-rmap
+++ a/mm/rmap.c
@@ -1199,7 +1199,7 @@ void page_add_anon_rmap(struct page *pag
atomic_t *mapped = &folio->_nr_pages_mapped;
int nr = 0, nr_pmdmapped = 0;
bool compound = flags & RMAP_COMPOUND;
- bool first = true;
+ bool first;
/* Is page being mapped by PTE? Is this its first map to be added? */
if (likely(!compound)) {
@@ -1228,9 +1228,6 @@ void page_add_anon_rmap(struct page *pag
}
}
- VM_BUG_ON_PAGE(!first && (flags & RMAP_EXCLUSIVE), page);
- VM_BUG_ON_PAGE(!first && PageAnonExclusive(page), page);
-
if (nr_pmdmapped)
__lruvec_stat_mod_folio(folio, NR_ANON_THPS, nr_pmdmapped);
if (nr)
@@ -1252,6 +1249,8 @@ void page_add_anon_rmap(struct page *pag
}
if (flags & RMAP_EXCLUSIVE)
SetPageAnonExclusive(page);
+ VM_WARN_ON_FOLIO(page_mapcount(page) > 1 && PageAnonExclusive(page),
+ folio);
mlock_vma_folio(folio, vma, compound);
}
@@ -2532,15 +2531,14 @@ void hugepage_add_anon_rmap(struct page
unsigned long address, rmap_t flags)
{
struct folio *folio = page_folio(page);
- int first;
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);
+ atomic_inc(&folio->_entire_mapcount);
if (flags & RMAP_EXCLUSIVE)
SetPageAnonExclusive(page);
+ VM_WARN_ON_FOLIO(folio_entire_mapcount(folio) > 1 &&
+ PageAnonExclusive(page), folio);
}
void hugepage_add_new_anon_rmap(struct folio *folio,
_
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
