From ae2c5d8042426b69c5f4a74296d1a20bb769a8ad Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Wed, 3 Jun 2020 16:00:17 -0700 Subject: [PATCH] khugepaged: drain LRU add pagevec after swapin collapse_huge_page() tries to swap in pages that are part of the PMD range. Just swapped in page goes though LRU add cache. The cache gets extra reference on the page. The extra reference can lead to the collapse fail: the following __collapse_huge_page_isolate() would check refcount and abort collapse seeing unexpected refcount. The fix is to drain local LRU add cache in __collapse_huge_page_swapin() if we successfully swapped in any pages. Signed-off-by: Kirill A. Shutemov Signed-off-by: Andrew Morton Tested-by: Zi Yan Reviewed-by: William Kucharski Reviewed-by: Zi Yan Acked-by: Yang Shi Cc: Andrea Arcangeli Cc: John Hubbard Cc: Mike Kravetz Cc: Ralph Campbell Link: http://lkml.kernel.org/r/20200416160026.16538-5-kirill.shutemov@linux.intel.com Signed-off-by: Linus Torvalds --- mm/khugepaged.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 8a74b9705a65..37d6c4be632f 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -931,6 +931,11 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, } vmf.pte--; pte_unmap(vmf.pte); + + /* Drain LRU add pagevec to remove extra pin on the swapped in pages */ + if (swapped_in) + lru_add_drain(); + trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1); return true; } -- GitLab