On Thu, Feb 10, 2022 at 10:17:27PM +0800, Miaohe Lin wrote: > It's unnecessary to walk the page table when vma_address() return -EFAULT. > Return early if so to save some cpu cycles. > > Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx> Acked-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> Does this patch fix the real problem rather than just saving cpu cycles? Without this patch, "address == -EFAULT" seems to make pgd_offset() return invalid pointer and result in some serious result like general protection fault. If that's the case, this patch might be worth sending to stable. Thanks, Naoya Horiguchi > --- > mm/memory-failure.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > index b3ff7e99a421..f86819145ea8 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -315,6 +315,8 @@ static unsigned long dev_pagemap_mapping_shift(struct page *page, > pmd_t *pmd; > pte_t *pte; > > + if (address == -EFAULT) > + return 0; > pgd = pgd_offset(vma->vm_mm, address); > if (!pgd_present(*pgd)) > return 0; > --- > 2.23.0 >
