Subject: + mm-track-vma-changes-with-vm_softdirty-bit-fix.patch added to -mm tree
To: gorcunov@xxxxxxxxx,akpm@xxxxxxxxxxxxxxxxxxxx,aneesh.kumar@xxxxxxxxxxxxxxxxxx,gorcunov@xxxxxxxxxx,kosaki.motohiro@xxxxxxxxx,luto@xxxxxxxxxxxxxx,mpm@xxxxxxxxxxx,mtosatti@xxxxxxxxxx,peterz@xxxxxxxxxxxxx,rdunlap@xxxxxxxxxxxxx,rob@xxxxxxxxxxx,sfr@xxxxxxxxxxxxxxxx,xemul@xxxxxxxxxxxxx,xiaoguangrong@xxxxxxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Tue, 20 Aug 2013 15:28:34 -0700
The patch titled
Subject: docs: Document soft dirty behaviour for freshly created memory regions, v2
has been added to the -mm tree. Its filename is
mm-track-vma-changes-with-vm_softdirty-bit-fix.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-track-vma-changes-with-vm_softdirty-bit-fix.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-track-vma-changes-with-vm_softdirty-bit-fix.patch
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------------------------------------------------------
From: Cyrill Gorcunov <gorcunov@xxxxxxxxx>
Subject: docs: Document soft dirty behaviour for freshly created memory regions, v2
Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Matt Mackall <mpm@xxxxxxxxxxx>
Cc: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
Cc: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxx>
Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: Rob Landley <rob@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/vm/soft-dirty.txt | 7 +++++++
1 file changed, 7 insertions(+)
diff -puN Documentation/vm/soft-dirty.txt~mm-track-vma-changes-with-vm_softdirty-bit-fix Documentation/vm/soft-dirty.txt
--- a/Documentation/vm/soft-dirty.txt~mm-track-vma-changes-with-vm_softdirty-bit-fix
+++ a/Documentation/vm/soft-dirty.txt
@@ -28,6 +28,13 @@ This is so, since the pages are still ma
the kernel does is finds this fact out and puts both writable and soft-dirty
bits on the PTE.
+ While in most cases tracking memory changes by #PF-s is more than enough
+there is still a scenario when we can lose soft dirty bits -- a task
+unmaps a previously mapped memory region and then maps a new one at exactly
+the same place. When unmap is called, the kernel internally clears PTE values
+including soft dirty bits. To notify user space application about such
+memory region renewal the kernel always marks new memory regions (and
+expanded regions) as soft dirty.
This feature is actively used by the checkpoint-restore project. You
can find more details about it on http://criu.org
_
Patches currently in -mm which might be from gorcunov@xxxxxxxxx are
arch-x86-include-asm-pgtable-2levelh-clean-up-pte_to_pgoff-and-pgoff_to_pte-helpers.patch
mm-track-vma-changes-with-vm_softdirty-bit.patch
mm-track-vma-changes-with-vm_softdirty-bit-fix.patch
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