[3.13.y.z extended stable] Patch "mm: softdirty: keep bit when zapping file pte" has been added to staging queue

Kamal Mostafa kamal at canonical.com
Thu Oct 9 20:51:48 UTC 2014

This is a note to let you know that I have just added a patch titled

    mm: softdirty: keep bit when zapping file pte

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:


This patch is scheduled to be released in version

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see



>From 092cb83d4fc82cdff1f8366bbf8c376cc25ff44a Mon Sep 17 00:00:00 2001
From: Peter Feiner <pfeiner at google.com>
Date: Thu, 25 Sep 2014 16:05:29 -0700
Subject: mm: softdirty: keep bit when zapping file pte

commit dbab31aa2ceec2d201966fa0b552f151310ba5f4 upstream.

This fixes the same bug as b43790eedd31 ("mm: softdirty: don't forget to
save file map softdiry bit on unmap") and 9aed8614af5a ("mm/memory.c:
don't forget to set softdirty on file mapped fault") where the return
value of pte_*mksoft_dirty was being ignored.

To be sure that no other pte/pmd "mk" function return values were being
ignored, I annotated the functions in arch/x86/include/asm/pgtable.h
with __must_check and rebuilt.

The userspace effect of this bug is that the softdirty mark might be
lost if a file mapped pte get zapped.

Signed-off-by: Peter Feiner <pfeiner at google.com>
Acked-by: Cyrill Gorcunov <gorcunov at openvz.org>
Cc: Pavel Emelyanov <xemul at parallels.com>
Cc: Jamie Liu <jamieliu at google.com>
Cc: Hugh Dickins <hughd at google.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
 mm/memory.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memory.c b/mm/memory.c
index d411f0d..e3c11e4 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1119,7 +1119,7 @@ again:
 						addr) != page->index) {
 				pte_t ptfile = pgoff_to_pte(page->index);
 				if (pte_soft_dirty(ptent))
-					pte_file_mksoft_dirty(ptfile);
+					ptfile = pte_file_mksoft_dirty(ptfile);
 				set_pte_at(mm, addr, pte, ptfile);
 			if (PageAnon(page))

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