The patch titled
Subject: mm: make swapoff more robust against soft dirty
has been added to the -mm tree. Its filename is
mm-make-swapoff-more-robust-against-soft-dirty.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-make-swapoff-more-robust-against-soft-dirty.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-make-swapoff-more-robust-against-soft-dirty.patch
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From: Hugh Dickins <hughd@xxxxxxxxxx>
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 <hughd@xxxxxxxxxx>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Acked-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
Cc: Laurent Dufour <ldufour@xxxxxxxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swapfile.c | 18 ++++--------------
1 file changed, 4 insertions(+), 14 deletions(-)
diff -puN mm/swapfile.c~mm-make-swapoff-more-robust-against-soft-dirty mm/swapfile.c
--- a/mm/swapfile.c~mm-make-swapoff-more-robust-against-soft-dirty
+++ a/mm/swapfile.c
@@ -1111,19 +1111,9 @@ unsigned int count_swap_pages(int type,
}
#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_stru
}
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_are
* 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)
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
mm-memcontrol-hook-up-vmpressure-to-socket-pressure-fix.patch
mm-make-swapoff-more-robust-against-soft-dirty.patch
powerpc-mm-fix-_page_swp_soft_dirty-breaking-swapoff.patch
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