[PATCH 3.13 146/163] mm: softdirty: keep bit when zapping file pte

From: Kamal Mostafa
Date: Thu Oct 09 2014 - 17:06:35 EST -stable review patch. If anyone has any objections, please let me know.


From: Peter Feiner <pfeiner@xxxxxxxxxx>

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@xxxxxxxxxx>
Acked-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Cc: Jamie Liu <jamieliu@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
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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