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authorCyrill Gorcunov <gorcunov@gmail.com>2013-08-13 19:00:49 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2013-08-13 20:57:47 -0400
commit179ef71cbc085252e3fe6b8159263a7ed1d88ea4 (patch)
tree423b58912b0bf0dc9697fff3d2205b8ca653968e /include/asm-generic
parent3e6b11df245180949938734bc192eaf32f3a06b3 (diff)
mm: save soft-dirty bits on swapped pages
Andy Lutomirski reported that if a page with _PAGE_SOFT_DIRTY bit set get swapped out, the bit is getting lost and no longer available when pte read back. To resolve this we introduce _PTE_SWP_SOFT_DIRTY bit which is saved in pte entry for the page being swapped out. When such page is to be read back from a swap cache we check for bit presence and if it's there we clear it and restore the former _PAGE_SOFT_DIRTY bit back. One of the problem was to find a place in pte entry where we can save the _PTE_SWP_SOFT_DIRTY bit while page is in swap. The _PAGE_PSE was chosen for that, it doesn't intersect with swap entry format stored in pte. Reported-by: Andy Lutomirski <luto@amacapital.net> Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org> Acked-by: Pavel Emelyanov <xemul@parallels.com> Cc: Matt Mackall <mpm@selenic.com> Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Peter Zijlstra <peterz@infradead.org> Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> Reviewed-by: Minchan Kim <minchan@kernel.org> Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/asm-generic')
-rw-r--r--include/asm-generic/pgtable.h15
1 files changed, 15 insertions, 0 deletions
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 2f47ade1b567..2a7e0d10ad9a 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -417,6 +417,21 @@ static inline pmd_t pmd_mksoft_dirty(pmd_t pmd)
417{ 417{
418 return pmd; 418 return pmd;
419} 419}
420
421static inline pte_t pte_swp_mksoft_dirty(pte_t pte)
422{
423 return pte;
424}
425
426static inline int pte_swp_soft_dirty(pte_t pte)
427{
428 return 0;
429}
430
431static inline pte_t pte_swp_clear_soft_dirty(pte_t pte)
432{
433 return pte;
434}
420#endif 435#endif
421 436
422#ifndef __HAVE_PFNMAP_TRACKING 437#ifndef __HAVE_PFNMAP_TRACKING