From d21b9e57c74ce82ac459e2ec8ce667db9b9da8b0 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Tue, 26 Jul 2016 15:25:37 -0700 Subject: [PATCH] thp: handle file pages in split_huge_pmd() Splitting THP PMD is simple: just unmap it as in DAX case. This way we can avoid memory overhead on page table allocation to deposit. It's probably a good idea to try to allocation page table with GFP_ATOMIC in __split_huge_pmd_locked() to avoid refaulting the area, but clearing pmd should be good enough for now. Unlike DAX, we also remove the page from rmap and drop reference. pmd_young() is transfered to PageReferenced(). Link: http://lkml.kernel.org/r/1466021202-61880-15-git-send-email-kirill.shutemov@linux.intel.com Signed-off-by: Kirill A. Shutemov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/huge_memory.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index d8ccd245947d..e6725c5c5a62 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2987,10 +2987,18 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, count_vm_event(THP_SPLIT_PMD); - if (vma_is_dax(vma)) { - pmd_t _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd); + if (!vma_is_anonymous(vma)) { + _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd); if (is_huge_zero_pmd(_pmd)) put_huge_zero_page(); + if (vma_is_dax(vma)) + return; + page = pmd_page(_pmd); + if (!PageReferenced(page) && pmd_young(_pmd)) + SetPageReferenced(page); + page_remove_rmap(page, true); + put_page(page); + add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR); return; } else if (is_huge_zero_pmd(*pmd)) { return __split_huge_zero_page_pmd(vma, haddr, pmd); -- 2.20.1