drm/i915: Ditch i915 globals shrink infrastructure

This essentially reverts

commit 84a1074920
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Wed Jan 24 11:36:08 2018 +0000

    drm/i915: Shrink the GEM kmem_caches upon idling

mm/vmscan.c:do_shrink_slab() is a thing, if there's an issue with it
then we need to fix that there, not hand-roll our own slab shrinking
code in i915.

Also when this was added there was only one other caller of
kmem_cache_shrink (added 2005 to the acpi code). Now there's a 2nd one
outside of i915 code in a kunit test, which seems legit since that
wants to very carefully control what's in the kmem_cache. This out of
a total of over 500 calls to kmem_cache_create. This alone should have
been warning sign enough that we're doing something silly.

Noticed while reviewing a patch set from Jason to fix up some issues
in our i915_init() and i915_exit() module load/cleanup code. Now that
i915_globals.c isn't any different than normal init/exit functions, we
should convert them over to one unified table and remove
i915_globals.[hc] entirely.

v2: Improve commit message (Jason)

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Cc: David Airlie <airlied@linux.ie>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210721183229.4136488-1-daniel.vetter@ffwll.ch

drivers/gpu/drm/i915/gem/i915_gem_context.c

@@ -2280,18 +2280,12 @@ i915_gem_engines_iter_next(struct i915_gem_engines_iter *it)
 #include "selftests/i915_gem_context.c"
 #endif
 
-static void i915_global_gem_context_shrink(void)
-{
-	kmem_cache_shrink(global.slab_luts);
-}
-
 static void i915_global_gem_context_exit(void)
 {
 	kmem_cache_destroy(global.slab_luts);
 }
 
 static struct i915_global_gem_context global = { {
-	.shrink = i915_global_gem_context_shrink,
 	.exit = i915_global_gem_context_exit,
 } };