[PATCH] drm/etnaviv: fix memory leak when mapping prime imported buffers

[Fuzzey, Martin]

Hi Lucas,

> Am Mittwoch, den 20.05.2020, 12:10 +0200 schrieb Martin Fuzzey:
> What's the use-case where you did hit this issue? mmap'ing of imported
> buffers through the etnaviv DRM device is currently not well defined
> and I was pondering the idea of forbidding it completely by not
> returning a mmap offset for those objects.
>

I hit this on Android 8 (on i.MX6 using mesa 20.0.6 with gbm gralloc
and drm hwcomposer)  and had a memory leak every time an activity was
started.
I'm not sure exactly why but Android does a gralloc.lock() and
gralloc.unlock() on every activity startup.
Those map and unmap the buffer.

Under Android (at least in 8+) the actual graphics buffer allocations
are done by a dedicated process
(android.hardware.graphics.allocator at 2.0-service)
because it uses a "binderized HAL" for the allocation
[https://source.android.com/devices/architecture/hal-types]
This means that buffers are *always* imported (though they are usually
only mmaped for SW rendering or screen shots).

Regards,

Martin