Re: [PATCH 16/42] drm/i915: Refactor object page API

[Joonas Lahtinen <joonas.lahtinen@linux.intel.com>]

On pe, 2016-10-07 at 10:46 +0100, Chris Wilson wrote:
> +static inline int __must_check
> +i915_gem_object_pin_pages(struct drm_i915_gem_object *obj)
>  {
> -	BUG_ON(obj->pages == NULL);
> -	obj->pages_pin_count++;
> +	lockdep_assert_held(&obj->base.dev->struct_mutex);

\n here.

> +	if (obj->mm.pages_pin_count++)
> +		return 0;
> +
> +	return __i915_gem_object_get_pages(obj);

I also second John here, what's up with the dummy wrapper convetion.
Add TODO comments if you intend to introduce new stuff relying on that.

> +}
> +
> +static inline void
> +__i915_gem_object_pin_pages(struct drm_i915_gem_object *obj)
> +{
> +	lockdep_assert_held(&obj->base.dev->struct_mutex);

Ditto.

> +	GEM_BUG_ON(!obj->mm.pages);
> +	obj->mm.pages_pin_count++;
> +}
> +
> +static inline bool
> +i915_gem_object_has_pinned_pages(struct drm_i915_gem_object *obj)
> +{
> +	return obj->mm.pages_pin_count;
> +}
> +
> +static inline void
> +__i915_gem_object_unpin_pages(struct drm_i915_gem_object *obj)
> +{
> +	lockdep_assert_held(&obj->base.dev->struct_mutex);
> +	GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
> +	GEM_BUG_ON(!obj->mm.pages);

\n at least here.

> +	obj->mm.pages_pin_count--;
>  }
>  

<SNIP>

> @@ -812,7 +809,7 @@ int i915_gem_obj_prepare_shmem_write(struct drm_i915_gem_object *obj,
>  		obj->cache_dirty = true;
>  
>  	intel_fb_obj_invalidate(obj, ORIGIN_CPU);
> -	obj->dirty = 1;
> +	obj->mm.dirty = true;

The type is not bool dirty : 1, do we get yelled at by compiler?

> @@ -1268,7 +1261,7 @@ i915_gem_gtt_pwrite_fast(struct drm_i915_private *i915,
>  		goto out_unpin;
>  
>  	intel_fb_obj_invalidate(obj, ORIGIN_CPU);
> -	obj->dirty = true;
> +	obj->mm.dirty = true;

I assume not as this has not been changed. Consistency is good anyway.

> @@ -2483,24 +2474,25 @@ i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
>  
>  	lockdep_assert_held(&obj->base.dev->struct_mutex);
>  
> -	if (obj->pages)
> +	if (obj->mm.pages)
>  		return 0;
>  
> -	if (obj->madv != I915_MADV_WILLNEED) {
> +	if (obj->mm.madv != I915_MADV_WILLNEED) {
>  		DRM_DEBUG("Attempting to obtain a purgeable object\n");
> +		__i915_gem_object_unpin_pages(obj);

Confusing to have teardown of another function in here.

>  		return -EFAULT;
>  	}
>  
> -	BUG_ON(obj->pages_pin_count);
> -
>  	ret = ops->get_pages(obj);
> -	if (ret)
> +	if (ret) {
> +		__i915_gem_object_unpin_pages(obj);

And if you like *really* have to, at least try not to duplicate code.
Bonus points form moving this to be proper teardown path where it has a
counter-part.

Strange side effects on failing function call do not lead to very
understandable code structure, but major spaghetti. Can be fixed in
follow-up patch too.

Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

Regards, Joonas
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
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