[Intel-gfx] [PATCH v2 1/2] drm/i915: Prevent a race during I915_GEM_MMAP ioctl with WC set

[Chris Wilson]

Quoting Joonas Lahtinen (2019-01-29 16:12:36)
> Make sure the underlying VMA in the process address space is the
> same as it was during vm_mmap to avoid applying WC to wrong VMA.
> 
> A more long-term solution would be to have vm_mmap_locked variant
> in linux/mmap.h for when caller wants to hold mmap_sem for an
> extended duration.
> 
> v2:
> - Refactor the compare function
> 
> Fixes: 1816f9236303 ("drm/i915: Support creation of unbound wc user mappings for objects")
> Reported-by: Adam Zabrocki <adamza at microsoft.com>
> Suggested-by: Linus Torvalds <torvalds at linux-foundation.org>
> Signed-off-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: <stable at vger.kernel.org> # v4.0+
> Cc: Akash Goel <akash.goel at intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
> Cc: Adam Zabrocki <adamza at microsoft.com>
> Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk> #v1
> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com> #v1
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris