[PATCH v2] mm/gup: fix gup_fast with dynamic page table folding

[Vasily Gorbik]

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