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authorCyrill Gorcunov <gorcunov@gmail.com>2013-08-13 16:00:49 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-08-13 17:57:47 -0700
commit179ef71cbc085252e3fe6b8159263a7ed1d88ea4 (patch)
tree423b58912b0bf0dc9697fff3d2205b8ca653968e /mm/memory.c
parent3e6b11df245180949938734bc192eaf32f3a06b3 (diff)
downloadop-kernel-dev-179ef71cbc085252e3fe6b8159263a7ed1d88ea4.zip
op-kernel-dev-179ef71cbc085252e3fe6b8159263a7ed1d88ea4.tar.gz
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 'mm/memory.c')
-rw-r--r--mm/memory.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/mm/memory.c b/mm/memory.c
index 1ce2e2a..e98ecad2 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3115,6 +3115,8 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
exclusive = 1;
}
flush_icache_page(vma, page);
+ if (pte_swp_soft_dirty(orig_pte))
+ pte = pte_mksoft_dirty(pte);
set_pte_at(mm, address, page_table, pte);
if (page == swapcache)
do_page_add_anon_rmap(page, vma, address, exclusive);
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