From 67f4c78b7f6e8b3db12ff0391ca8af66afb7db89 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Mon, 2 Aug 2021 11:00:41 +0800 Subject: [PATCH] mm/thp: another PVMW_SYNC fix in page_vma_mapped_walk() stable inclusion from linux-4.19.197 commit e943b4373cf706ee8ee433988bc0c4d6e3ea5907 -------------------------------- [ Upstream commit a7a69d8ba88d8dcee7ef00e91d413a4bd003a814 ] Aha! Shouldn't that quick scan over pte_none()s make sure that it holds ptlock in the PVMW_SYNC case? That too might have been responsible for BUGs or WARNs in split_huge_page_to_list() or its unmap_page(), though I've never seen any. Link: https://lkml.kernel.org/r/1bdf384c-8137-a149-2a1e-475a4791c3c@google.com Link: https://lore.kernel.org/linux-mm/20210412180659.B9E3.409509F4@e16-tech.com/ Fixes: ace71a19cec5 ("mm: introduce page_vma_mapped_walk()") Signed-off-by: Hugh Dickins Acked-by: Kirill A. Shutemov Tested-by: Wang Yugui Cc: Alistair Popple Cc: Matthew Wilcox Cc: Peter Xu Cc: Ralph Campbell Cc: Will Deacon Cc: Yang Shi Cc: Zi Yan Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin Signed-off-by: Yang Yingliang --- mm/page_vma_mapped.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c index b7a8009c1549..edca78609318 100644 --- a/mm/page_vma_mapped.c +++ b/mm/page_vma_mapped.c @@ -272,6 +272,10 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) goto restart; } pvmw->pte++; + if ((pvmw->flags & PVMW_SYNC) && !pvmw->ptl) { + pvmw->ptl = pte_lockptr(mm, pvmw->pmd); + spin_lock(pvmw->ptl); + } } while (pte_none(*pvmw->pte)); if (!pvmw->ptl) { -- GitLab