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Date: Thu, 3 Mar 2016 19:52:04 +0300 From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> To: Hugh Dickins <hughd@...gle.com>, Andrea Arcangeli <aarcange@...hat.com>, Andrew Morton <akpm@...ux-foundation.org> Cc: Dave Hansen <dave.hansen@...el.com>, Vlastimil Babka <vbabka@...e.cz>, Christoph Lameter <cl@...two.org>, Naoya Horiguchi <n-horiguchi@...jp.nec.com>, Jerome Marchand <jmarchan@...hat.com>, Yang Shi <yang.shi@...aro.org>, Sasha Levin <sasha.levin@...cle.com>, linux-kernel@...r.kernel.org, linux-mm@...ck.org, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> Subject: [PATCHv3 14/29] 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. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.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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