From: Kirill A. Shutemov Date: Tue, 26 Jul 2016 22:25:40 +0000 (-0700) Subject: thp: handle file COW faults X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=af9e4d5f2de2eabdc7145e077ba48b2a638465c6;p=openwrt%2Fstaging%2Fblogic.git thp: handle file COW faults File COW for THP is handled on pte level: just split the pmd. It's not clear how benefitial would be allocation of huge pages on COW faults. And it would require some code to make them work. I think at some point we can consider teaching khugepaged to collapse pages in COW mappings, but allocating huge on fault is probably overkill. Link: http://lkml.kernel.org/r/1466021202-61880-16-git-send-email-kirill.shutemov@linux.intel.com Signed-off-by: Kirill A. Shutemov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/memory.c b/mm/memory.c index 10a424eca8a4..8f4254798130 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3446,6 +3446,11 @@ static int wp_huge_pmd(struct fault_env *fe, pmd_t orig_pmd) if (fe->vma->vm_ops->pmd_fault) return fe->vma->vm_ops->pmd_fault(fe->vma, fe->address, fe->pmd, fe->flags); + + /* COW handled on pte level: split pmd */ + VM_BUG_ON_VMA(fe->vma->vm_flags & VM_SHARED, fe->vma); + split_huge_pmd(fe->vma, fe->pmd, fe->address); + return VM_FAULT_FALLBACK; }