drm/i915: If we hit OOM when allocating GTT pages, clear the aperture

Rather than evicting an object at random, which is unlikely to alleviate
the memory pressure sufficient to allow us to continue, zap the entire
aperture. That should give the system long enough to recover and reap
some pages from the evicted objects, forestalling the allocation error
for the new object.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_gem.c

@@ -2782,10 +2782,8 @@ i915_gem_object_bind_to_gtt(struct drm_i915_gem_object *obj,
 		obj->gtt_space = NULL;
 
 		if (ret == -ENOMEM) {
-			/* first try to clear up some space from the GTT */
-			ret = i915_gem_evict_something(dev, size,
-						       alignment,
-						       map_and_fenceable);
+			/* first try to reclaim some memory by clearing the GTT */
+			ret = i915_gem_evict_everything(dev, false);
 			if (ret) {
 				/* now try to shrink everyone else */
 				if (gfpmask) {
@@ -2793,7 +2791,7 @@ i915_gem_object_bind_to_gtt(struct drm_i915_gem_object *obj,
 					goto search_free;
 				}
 
-				return ret;
+				return -ENOMEM;
 			}
 
 			goto search_free;
@@ -2808,9 +2806,7 @@ i915_gem_object_bind_to_gtt(struct drm_i915_gem_object *obj,
 		drm_mm_put_block(obj->gtt_space);
 		obj->gtt_space = NULL;
 
-		ret = i915_gem_evict_something(dev, size,
-					       alignment, map_and_fenceable);
-		if (ret)
+		if (i915_gem_evict_everything(dev, false))
 			return ret;
 
 		goto search_free;