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[PATCHv9-rebased 09/32] 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 1ffd53de82ce..c9473faea7aa 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2994,10 +2994,18 @@ 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 00/32] THP-enabled tmpfs/shmem using compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-06 16:20 +0200
  [PATCHv9 11/32] thp: skip file huge pmd on copy_huge_pmd() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-06 16:20 +0200
  [PATCHv9 09/32] thp: handle file pages in split_huge_pmd() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-06 16:30 +0200
  [PATCHv9 06/32] mm: introduce do_set_pmd() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-06 16:30 +0200
  [PATCHv9 13/32] thp: run vma_adjust_trans_huge() outside i_mmap_rwsem "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-06 16:30 +0200
  [PATCHv9 04/32] mm: postpone page table allocation until we have page to map "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-06 16:30 +0200
  [PATCHv9-rebased 24/32] shmem: add huge pages support "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:10 +0200
  [PATCHv9-rebased 25/32] shmem, thp: respect MADV_{NO,}HUGEPAGE for file mappings "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:10 +0200
  [PATCHv9-rebased 06/32] mm: introduce do_set_pmd() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:10 +0200
  [PATCHv9-rebased 16/32] vmscan: split file huge pages before paging them out "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:10 +0200
  [PATCHv9-rebased 07/32] thp, vmstats: add counters for huge file pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:10 +0200
  [PATCHv9-rebased 23/32] shmem: get_unmapped_area align huge page "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:10 +0200
  [PATCHv9-rebased 19/32] filemap: prepare find and delete operations for huge pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:10 +0200
  [PATCHv9-rebased 30/32] thp: introduce CONFIG_TRANSPARENT_HUGE_PAGECACHE "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:10 +0200
  [PATCHv9-rebased 01/32] thp, mlock: update unevictable-lru.txt "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:10 +0200
  [PATCHv9-rebased 13/32] thp: run vma_adjust_trans_huge() outside i_mmap_rwsem "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:10 +0200
  [PATCHv9-rebased 04/32] mm: postpone page table allocation until we have page to map "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:10 +0200
  [PATCHv9-rebased 28/32] shmem: make shmem_inode_info::lock irq-safe "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:10 +0200
  [PATCHv9-rebased 32/32] thp: update Documentation/{vm/transhuge,filesystems/proc}.txt "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:10 +0200
  [PATCHv9-rebased 27/32] khugepaged: move up_read(mmap_sem) out of khugepaged_alloc_page() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:10 +0200
  [PATCHv9-rebased 10/32] thp: handle file COW faults "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:10 +0200
  [PATCHv9-rebased 29/32] khugepaged: add support of collapse for tmpfs/shmem pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:10 +0200
  [PATCHv9-rebased 31/32] shmem: split huge pages beyond i_size under memory pressure "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:10 +0200
  [PATCHv9-rebased 02/32] mm: do not pass mm_struct into handle_mm_fault "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:20 +0200
  [PATCHv9-rebased 21/32] mm, rmap: account shmem thp pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:20 +0200
  [PATCHv9-rebased 12/32] thp: prepare change_huge_pmd() for file thp "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:20 +0200
  [PATCHv9-rebased 08/32] thp: support file pages in zap_huge_pmd() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:20 +0200
  [PATCHv9-rebased 05/32] rmap: support file thp "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:20 +0200
  [PATCHv9-rebased 11/32] thp: skip file huge pmd on copy_huge_pmd() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:20 +0200
  [PATCHv9-rebased 00/32] THP-enabled tmpfs/shmem using compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:20 +0200
    [PATCHv9-rebased 22/32] shmem: prepare huge= mount option and sysfs knob "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:20 +0200
    [PATCHv9-rebased 15/32] thp, mlock: do not mlock PTE-mapped file huge pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:20 +0200
    [PATCHv9-rebased 17/32] page-flags: relax policy for PG_mappedtodisk and PG_reclaim "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:20 +0200
    [PATCHv9-rebased 20/32] truncate: handle file thp "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:20 +0200
    [PATCHv9-rebased 18/32] radix-tree: implement radix_tree_maybe_preload_order() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:20 +0200
    [PATCHv9-rebased 09/32] thp: handle file pages in split_huge_pmd() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:20 +0200
    [PATCHv9-rebased 14/32] thp: file pages support for split_huge_page() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-06-07 13:20 +0200

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