From f707fa493784b515ced01d4e261afe16fc784b5d Mon Sep 17 00:00:00 2001 From: Yang Shi Date: Thu, 16 Jun 2022 10:48:36 -0700 Subject: [PATCH] mm: khugepaged: better comments for anon vma check in hugepage_vma_revalidate The hugepage_vma_revalidate() needs to check if the vma is still anonymous vma or not since the address may be unmapped then remapped to file before khugepaged reaquired the mmap_lock. The old comment is not quite helpful, elaborate this with better comment. Link: https://lkml.kernel.org/r/20220616174840.1202070-4-shy828301@gmail.com Signed-off-by: Yang Shi Reviewed-by: Zach O'Keefe Cc: Kirill A. Shutemov Cc: Matthew Wilcox Cc: Miaohe Lin Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- mm/khugepaged.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index c7e2213..67e144e 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -958,7 +958,13 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, return SCAN_ADDRESS_RANGE; if (!hugepage_vma_check(vma, vma->vm_flags)) return SCAN_VMA_CHECK; - /* Anon VMA expected */ + /* + * Anon VMA expected, the address may be unmapped then + * remapped to file after khugepaged reaquired the mmap_lock. + * + * hugepage_vma_check may return true for qualified file + * vmas. + */ if (!vma->anon_vma || !vma_is_anonymous(vma)) return SCAN_VMA_CHECK; return 0; -- 2.7.4