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authorCyrill Gorcunov <gorcunov@gmail.com>2013-08-14 03:00:49 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2013-08-14 04:57:47 +0400
commit179ef71cbc085252e3fe6b8159263a7ed1d88ea4 (patch)
tree423b58912b0bf0dc9697fff3d2205b8ca653968e /fs
parent3e6b11df245180949938734bc192eaf32f3a06b3 (diff)
downloadlinux-179ef71cbc085252e3fe6b8159263a7ed1d88ea4.tar.xz
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 'fs')
-rw-r--r--fs/proc/task_mmu.c21
1 files changed, 15 insertions, 6 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index dbf61f6174f0..e2d9bdce5e7e 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -730,8 +730,14 @@ static inline void clear_soft_dirty(struct vm_area_struct *vma,
* of how soft-dirty works.
*/
pte_t ptent = *pte;
- ptent = pte_wrprotect(ptent);
- ptent = pte_clear_flags(ptent, _PAGE_SOFT_DIRTY);
+
+ if (pte_present(ptent)) {
+ ptent = pte_wrprotect(ptent);
+ ptent = pte_clear_flags(ptent, _PAGE_SOFT_DIRTY);
+ } else if (is_swap_pte(ptent)) {
+ ptent = pte_swp_clear_soft_dirty(ptent);
+ }
+
set_pte_at(vma->vm_mm, addr, pte, ptent);
#endif
}
@@ -752,14 +758,15 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,
pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
for (; addr != end; pte++, addr += PAGE_SIZE) {
ptent = *pte;
- if (!pte_present(ptent))
- continue;
if (cp->type == CLEAR_REFS_SOFT_DIRTY) {
clear_soft_dirty(vma, addr, pte);
continue;
}
+ if (!pte_present(ptent))
+ continue;
+
page = vm_normal_page(vma, addr, ptent);
if (!page)
continue;
@@ -930,8 +937,10 @@ static void pte_to_pagemap_entry(pagemap_entry_t *pme, struct pagemapread *pm,
flags = PM_PRESENT;
page = vm_normal_page(vma, addr, pte);
} else if (is_swap_pte(pte)) {
- swp_entry_t entry = pte_to_swp_entry(pte);
-
+ swp_entry_t entry;
+ if (pte_swp_soft_dirty(pte))
+ flags2 |= __PM_SOFT_DIRTY;
+ entry = pte_to_swp_entry(pte);
frame = swp_type(entry) |
(swp_offset(entry) << MAX_SWAPFILES_SHIFT);
flags = PM_SWAP;