[Intel-gfx] improve use_mm / unuse_mm v2

[Christoph Hellwig]

On Thu, Apr 16, 2020 at 08:17:44PM -0700, Matthew Wilcox wrote:
> On Thu, Apr 16, 2020 at 07:31:55AM +0200, Christoph Hellwig wrote:
> > this series improves the use_mm / unuse_mm interface by better
> > documenting the assumptions, and my taking the set_fs manipulations
> > spread over the callers into the core API.
> 
> I appreciate all the work you're doing here.
> 
> Do you have plans to introduce a better-named API than set_fs() / get_fs()?

Eventually.  For now I just plan to kill as many as possible.

> Also, having set_fs() return the previous value of 'fs' would simplify
> a lot of the callers.

One thing that should go relatively soon is the need to store the
previous value because we'll have so few callers left that we know we can't
recurse. We should be able to get there around 5.9 / 5.10.