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[PATCHv9-rebased2 14/37] thp: handle file pages in split_huge_pmd()

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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().

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 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 d8fd49073280..f10febd4f6e1 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2991,10 +2991,18 @@ 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);
-- 
2.8.1

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[PATCHv9-rebased2 00/37] THP-enabled tmpfs/shmem using compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 05/37] khugepaged: recheck pmd after mmap_sem re-acquired "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
    Re: [PATCHv9-rebased2 05/37] khugepaged: recheck pmd after mmap_sem  re-acquired Ebru Akagunduz <ebru.akagunduz@gmail.com> - 2016-06-16 13:50 +0200
      Re: [PATCHv9-rebased2 05/37] khugepaged: recheck pmd after mmap_sem  re-acquired "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-06-16 14:00 +0200
  [PATCHv9-rebased2 12/37] thp, vmstats: add counters for huge file pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 17/37] thp: prepare change_huge_pmd() for file thp "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 09/37] mm: postpone page table allocation until we have page to map "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 18/37] thp: run vma_adjust_trans_huge() outside i_mmap_rwsem "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 21/37] vmscan: split file huge pages before paging them out "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 13/37] thp: support file pages in zap_huge_pmd() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 29/37] shmem: add huge pages support "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 06/37] thp, mlock: update unevictable-lru.txt "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 19/37] thp: file pages support for split_huge_page() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 28/37] shmem: get_unmapped_area align huge page "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 07/37] mm: do not pass mm_struct into handle_mm_fault "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 34/37] khugepaged: add support of collapse for tmpfs/shmem pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 14/37] thp: handle file pages in split_huge_pmd() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 11/37] mm: introduce do_set_pmd() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 26/37] mm, rmap: account shmem thp pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 25/37] truncate: handle file thp "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 24/37] filemap: prepare find and delete operations for huge pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 22/37] page-flags: relax policy for PG_mappedtodisk and PG_reclaim "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 27/37] shmem: prepare huge= mount option and sysfs knob "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 10/37] rmap: support file thp "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:20 +0200
  [PATCHv9-rebased2 04/37]  mm-thp-make-swapin-readahead-under-down_read-of-mmap_sem-fix-2-fix "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-15 22:30 +0200

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