From: Peter Feiner <pfeiner@google.com>
Date: Thu, 25 Sep 2014 23:05:29 +0000 (-0700)
Subject: mm: softdirty: keep bit when zapping file pte
X-Git-Tag: v3.17-rc7~9^2
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=dbab31aa2ceec2d201966fa0b552f151310ba5f4;p=platform%2Fkernel%2Flinux-stable.git

mm: softdirty: keep bit when zapping file pte

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@google.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Jamie Liu <jamieliu@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>	[3.12+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/memory.c b/mm/memory.c
index d17f1bc..e229970 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1127,7 +1127,7 @@ 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))