[RFC 0/3] arm: support get_user_pages_fast

[minchan@kernel.org (Minchan Kim)]

Recently, I got a report get_user_pages_fast helps app's launching time
due to reducing uninterruptible sleep time because it could reduce
mmap_sem lock contentions when app is launching.

To support gupf in ARM-non-LPAE, first patch reorders memory type table
to use 5th bit of the page table. It seems we don't use the bit in ARMv6+
but it needs double check from maintainers.

Second patch introduces L_PTE_SPECIAL for arm so that last patch can
support get_user_pags_fast.

I would greatly appreciate if guys review that I screw up something,
especially, architecture stuffs.

Thanks.

Minchan Kim (3):
  arm: mm: reordering memory type table
  arm: mm: introduce L_PTE_SPECIAL
  arm: mm: support get_user_pages_fast

 arch/arm/Kconfig                      |   2 +-
 arch/arm/include/asm/pgtable-2level.h |  16 +-
 arch/arm/include/asm/pgtable-3level.h |   6 -
 arch/arm/include/asm/pgtable.h        |  13 ++
 arch/arm/mm/Makefile                  |   6 +
 arch/arm/mm/gup.c                     | 221 ++++++++++++++++++++++++++
 arch/arm/mm/proc-macros.S             |  16 +-
 7 files changed, 261 insertions(+), 19 deletions(-)
 create mode 100644 arch/arm/mm/gup.c

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2.19.0.rc1.350.ge57e33dbd1-goog