Messages in this thread Patch in this message | | | Date | Mon, 18 Sep 2023 11:59:03 +0200 | Subject | Re: [PATCH v1 5/6] mm/rmap: simplify PageAnonExclusive sanity checks when adding anon rmap | From | David Hildenbrand <> |
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On 13.09.23 14:51, David Hildenbrand wrote: > 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(). > > Signed-off-by: David Hildenbrand <david@redhat.com> > ---
Hi Andrew, the following fixup on top:
From 4b945ca15817b491123cc922f022b253134075b7 Mon Sep 17 00:00:00 2001 From: David Hildenbrand <david@redhat.com> Date: Mon, 18 Sep 2023 11:16:57 +0200 Subject: [PATCH] fixup: mm/rmap: simplify PageAnonExclusive sanity checks when adding anon rmap
While PTE-mapping a THP, we temporarily have an exclusive page of a THP mapped by both, a PMD and a PTE at the same time. Update our check to allow for that combination.
Reported-by: syzbot+6e4f59235036c3c2e296@syzkaller.appspotmail.com Signed-off-by: David Hildenbrand <david@redhat.com> --- mm/rmap.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c index 789a2beb8b3a..f13a2927163d 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1249,8 +1249,10 @@ void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma, } if (flags & RMAP_EXCLUSIVE) SetPageAnonExclusive(page); - VM_WARN_ON_FOLIO(page_mapcount(page) > 1 && PageAnonExclusive(page), - folio); + /* While PTE-mapping a THP we have a PMD and a PTE mapping. */ + VM_WARN_ON_FOLIO((atomic_read(&page->_mapcount) > 0 || + (folio_test_large(folio) && folio_entire_mapcount(folio) > 1)) && + PageAnonExclusive(page), folio); mlock_vma_folio(folio, vma, compound); } -- 2.41.0
-- Cheers,
David / dhildenb
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