On Mon,  7 Jul 2014 09:53:56 +0900
Minchan Kim [off-list ref] wrote:

MADV_FREE needs pmd_dirty and pmd_mkclean for detecting recent
overwrite of the contents since MADV_FREE syscall is called for
THP page but for s390 pmds only referenced bit is available
because there is no free bit left in the pmd entry for the
software dirty bit so this patch adds dumb pmd_dirty which
returns always true by suggesting by Martin.

They finally find a solution in future.
http://marc.info/?l=linux-api&m=140440328820808&w=2

Cc: Martin Schwidefsky <redacted>
Cc: Heiko Carstens <redacted>
Cc: Gerald Schaefer <redacted>
Cc: Dominik Dingel <redacted>
Cc: Christian Borntraeger <redacted>
Cc: linux-s390-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Signed-off-by: Minchan Kim <redacted>
---
 arch/s390/include/asm/pgtable.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

Acked-by: Gerald Schaefer <redacted>