[PATCH] drm/shmem-helper: Don't remove the offset in vm_area_struct pgoff

[Alyssa Rosenzweig]

> Yeah plus Cc: stable for backporting and I think an igt or similar for
> panfrost to check this works correctly would be pretty good too. Since
> if it took us over 1 year to notice this bug it's pretty clear that
> normal testing doesn't catch this. So very likely we'll break this
> again.

Unfortunately there are a lot of kernel bugs which are noticed during actual
use (but not CI runs), some of which have never been fixed. I do know
the shrinker impl is buggy for us, if this is the fix I'm very happy.

> btw for testing shrinkers recommended way is to have a debugfs file
> that just force-shrinks everything. That way you avoid all the trouble
> that tend to happen when you drive a system close to OOM on linux, and
> it's also much faster.

2nding this as a good idea.