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| author | Hugh Dickins <hughd@google.com> | 2016-01-15 16:57:34 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-01-15 17:56:32 -0800 |
| commit | 9f8bdb3f3dad3f8f20df3e8903316cd5bb1c408e (patch) | |
| tree | 5e1eb6e9a27377d4738ada576a2456629a310a27 /mm/swapfile.c | |
| parent | 88f306b68cbb36e500da4b9601b2e3d13dd683c4 (diff) | |
| download | lwn-9f8bdb3f3dad3f8f20df3e8903316cd5bb1c408e.tar.gz lwn-9f8bdb3f3dad3f8f20df3e8903316cd5bb1c408e.zip | |
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 <hughd@google.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/swapfile.c')
| -rw-r--r-- | mm/swapfile.c | 18 |
1 files changed, 4 insertions, 14 deletions
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) |