drm/i915: blow away userspace mappings before fence change

This aligns it with the other user of i915_gem_clear_fence_reg,
which blows away the mapping before changing the fence reg.

Only affects userspace if it races against itself when changing
tiling parameters, i.e. behaviour is undefined, anyway.
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/i915_gem.c

@@ -2544,6 +2544,12 @@ i915_gem_object_put_fence_reg(struct drm_gem_object *obj)
 	if (obj_priv->fence_reg == I915_FENCE_REG_NONE)
 		return 0;
 
+	/* If we've changed tiling, GTT-mappings of the object
+	 * need to re-fault to ensure that the correct fence register
+	 * setup is in place.
+	 */
+	i915_gem_release_mmap(obj);
+
 	/* On the i915, GPU access to tiled buffers is via a fence,
 	 * therefore we must wait for any outstanding access to complete
 	 * before clearing the fence.

drivers/gpu/drm/i915/i915_gem_tiling.c

@@ -371,12 +371,6 @@ i915_gem_set_tiling(struct drm_device *dev, void *data,
 			goto err;
 		}
 
-		/* If we've changed tiling, GTT-mappings of the object
-		 * need to re-fault to ensure that the correct fence register
-		 * setup is in place.
-		 */
-		i915_gem_release_mmap(obj);
-
 		obj_priv->tiling_mode = args->tiling_mode;
 		obj_priv->stride = args->stride;
 	}