| From | "Kirill A. Shutemov" <> | Subject | [PATCHv3 14/29] thp: handle file COW faults | Date | Thu, 3 Mar 2016 19:52:04 +0300 |
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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.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> --- mm/memory.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/mm/memory.c b/mm/memory.c index ab9acc4d83a2..0acdd33bfe16 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3369,6 +3369,11 @@ 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; } -- 2.7.0
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