Commit af9e4d5f authored Jul 26, 2016 by Kirill A. Shutemov Committed by Linus Torvalds Jul 26, 2016

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 <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent d21b9e57

mm/memory.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -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;
		}