On Fri, Sep 11, 2020 at 10:36:43PM +0200, Vasily Gorbik wrote:

Currently to make sure that every page table entry is read just once
gup_fast walks perform READ_ONCE and pass pXd value down to the next
gup_pXd_range function by value e.g.:

...snip...

---
v2: added brackets &pgd -> &(pgd)

 arch/s390/include/asm/pgtable.h | 42 +++++++++++++++++++++++----------
 include/linux/pgtable.h         | 10 ++++++++
 mm/gup.c                        | 18 +++++++-------
 3 files changed, 49 insertions(+), 21 deletions(-)

Andrew, any chance you would pick this up?

There is an Ack from Linus. And I haven't seen any objections from Jason or John.
This seems to be as safe for other architectures as possible.

@Jason and John
Any acks/nacks?

Thank you,
Vasily