From 9f8bdb3f3dad3f8f20df3e8903316cd5bb1c408e Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Fri, 15 Jan 2016 16:57:34 -0800 Subject: mm: make swapoff more robust against soft dirty Both s390 and powerpc have hit the issue of swapoff hanging, when CONFIG_HAVE_ARCH_SOFT_DIRTY and CONFIG_MEM_SOFT_DIRTY ifdefs were not quite as x86_64 had them. I think it would be much clearer if HAVE_ARCH_SOFT_DIRTY was just a Kconfig option set by architectures to determine whether the MEM_SOFT_DIRTY option should be offered, and the actual code depend upon CONFIG_MEM_SOFT_DIRTY alone. But won't embark on that change myself: instead make swapoff more robust, by using pte_swp_clear_soft_dirty() on each pte it encounters, without an explicit #ifdef CONFIG_MEM_SOFT_DIRTY. That being a no-op, whether the bit in question is defined as 0 or the asm-generic fallback is used, unless soft dirty is fully turned on. Why "maybe" in maybe_same_pte()? Rename it pte_same_as_swp(). Signed-off-by: Hugh Dickins Reviewed-by: Aneesh Kumar K.V Acked-by: Cyrill Gorcunov Cc: Laurent Dufour Cc: Michael Ellerman Cc: Martin Schwidefsky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/swapfile.c | 18 ++++-------------- 1 file changed, 4 insertions(+), 14 deletions(-) (limited to 'mm/swapfile.c') diff --git a/mm/swapfile.c b/mm/swapfile.c index 31dc94fb0f60..2bb30aa3a412 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1111,19 +1111,9 @@ unsigned int count_swap_pages(int type, int free) } #endif /* CONFIG_HIBERNATION */ -static inline int maybe_same_pte(pte_t pte, pte_t swp_pte) +static inline int pte_same_as_swp(pte_t pte, pte_t swp_pte) { -#ifdef CONFIG_MEM_SOFT_DIRTY - /* - * When pte keeps soft dirty bit the pte generated - * from swap entry does not has it, still it's same - * pte from logical point of view. - */ - pte_t swp_pte_dirty = pte_swp_mksoft_dirty(swp_pte); - return pte_same(pte, swp_pte) || pte_same(pte, swp_pte_dirty); -#else - return pte_same(pte, swp_pte); -#endif + return pte_same(pte_swp_clear_soft_dirty(pte), swp_pte); } /* @@ -1152,7 +1142,7 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, } pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); - if (unlikely(!maybe_same_pte(*pte, swp_entry_to_pte(entry)))) { + if (unlikely(!pte_same_as_swp(*pte, swp_entry_to_pte(entry)))) { mem_cgroup_cancel_charge(page, memcg, false); ret = 0; goto out; @@ -1210,7 +1200,7 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd, * swapoff spends a _lot_ of time in this loop! * Test inline before going to call unuse_pte. */ - if (unlikely(maybe_same_pte(*pte, swp_pte))) { + if (unlikely(pte_same_as_swp(*pte, swp_pte))) { pte_unmap(pte); ret = unuse_pte(vma, pmd, addr, entry, page); if (ret) -- cgit v1.2.3-58-ga151