From d670ffd87509b6b136d8ed6f757851a8ebe442b2 Mon Sep 17 00:00:00 2001 From: "Aneesh Kumar K.V" Date: Tue, 10 Jan 2017 16:57:18 -0800 Subject: [PATCH] mm/thp/pagecache/collapse: free the pte page table on collapse for thp page cache. With THP page cache, when trying to build a huge page from regular pte pages, we just clear the pmd entry. We will take another fault and at that point we will find the huge page in the radix tree, thereby using the huge page to complete the page fault The second fault path will allocate the needed pgtable_t page for archs like ppc64. So no need to deposit the same in collapse path. Depositing them in the collapse path resulting in a pgtable_t memory leak also giving errors like BUG: non-zero nr_ptes on freeing mm: 3 Fixes: 953c66c2b22a ("mm: THP page cache support for ppc64") Link: http://lkml.kernel.org/r/20161212163428.6780-2-aneesh.kumar@linux.vnet.ibm.com Signed-off-by: Aneesh Kumar K.V Acked-by: Kirill A. Shutemov Cc: Michael Ellerman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/khugepaged.c | 21 ++------------------- 1 file changed, 2 insertions(+), 19 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index e32389a97030..b0924a68cc36 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1242,7 +1242,6 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) struct vm_area_struct *vma; unsigned long addr; pmd_t *pmd, _pmd; - bool deposited = false; i_mmap_lock_write(mapping); vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) { @@ -1267,26 +1266,10 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) spinlock_t *ptl = pmd_lock(vma->vm_mm, pmd); /* assume page table is clear */ _pmd = pmdp_collapse_flush(vma, addr, pmd); - /* - * now deposit the pgtable for arch that need it - * otherwise free it. - */ - if (arch_needs_pgtable_deposit()) { - /* - * The deposit should be visibile only after - * collapse is seen by others. - */ - smp_wmb(); - pgtable_trans_huge_deposit(vma->vm_mm, pmd, - pmd_pgtable(_pmd)); - deposited = true; - } spin_unlock(ptl); up_write(&vma->vm_mm->mmap_sem); - if (!deposited) { - atomic_long_dec(&vma->vm_mm->nr_ptes); - pte_free(vma->vm_mm, pmd_pgtable(_pmd)); - } + atomic_long_dec(&vma->vm_mm->nr_ptes); + pte_free(vma->vm_mm, pmd_pgtable(_pmd)); } } i_mmap_unlock_write(mapping); -- 2.39.5