The patch titled
Subject: mm/rmap: warn on new PTE-mapped folios in page_add_anon_rmap()
has been added to the -mm mm-unstable branch. Its filename is
mm-rmap-warn-on-new-pte-mapped-folios-in-page_add_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-warn-on-new-pte-mapped-folios-in-page_add_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: warn on new PTE-mapped folios in page_add_anon_rmap()
Date: Wed, 13 Sep 2023 14:51:11 +0200
If swapin code would ever decide to not use order-0 pages and supply a
PTE-mapped large folio, we will have to change how we call
__folio_set_anon() -- eventually with exclusive=false and an adjusted
address. For now, let's add a VM_WARN_ON_FOLIO() with a comment about the
situation.
Link: https://lkml.kernel.org/r/20230913125113.313322-5-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 | 7 +++++++
1 file changed, 7 insertions(+)
--- a/mm/rmap.c~mm-rmap-warn-on-new-pte-mapped-folios-in-page_add_anon_rmap
+++ a/mm/rmap.c
@@ -1238,6 +1238,13 @@ void page_add_anon_rmap(struct page *pag
if (unlikely(!folio_test_anon(folio))) {
VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio);
+ /*
+ * For a PTE-mapped large folio, we only know that the single
+ * PTE is exclusive. Further, __folio_set_anon() might not get
+ * folio->index right when not given the address of the head
+ * page.
+ */
+ VM_WARN_ON_FOLIO(folio_test_large(folio) && !compound, folio);
__folio_set_anon(folio, vma, address,
!!(flags & RMAP_EXCLUSIVE));
} else if (likely(!folio_test_ksm(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
