[Intel-gfx] add remap_pfn_range_notrack instead of reinventing it in i915

[Christoph Hellwig]

Hi all,

i915 has some reason to want to avoid the track_pfn_remap overhead in
remap_pfn_range.  Add a function to the core VM to do just that rather
than reinventing the functionality poorly in the driver.

Note that the remap_io_sg path does get exercises when using Xorg on my
Thinkpad X1, so this should be considered lightly tested, I've not
managed to hit the remap_io_mapping path at all.


Diffstat:
 drivers/gpu/drm/i915/i915_mm.c |  101 ++++++++++-------------------------------
 include/linux/mm.h             |    2 
 mm/memory.c                    |   52 ++++++++++++---------
 3 files changed, 60 insertions(+), 95 deletions(-)