Re: [PATCH] drm/i915: Propagate error from drm_gem_object_init()

[Dave Gordon <david.s.gordon@intel.com>]

On 22/04/16 11:57, Matthew Auld wrote:
> From: Chris Wilson <chris@chris-wilson.co.uk>
>
> Propagate the real error from drm_gem_object_init(). Note this also
> fixes some confusion in the error return from i915_gem_alloc_object...
>
> v2:
> (Matthew Auld)
>    - updated new users of gem_alloc_object from latest drm-nightly
>    - replaced occurrences of IS_ERR_OR_NULL() with IS_ERR()
> v3:
> (Joonas Lahtinen)
>    - fix double "From:" in commit message
>    - add goto teardown path
>
> Signed-off-by: Matthew Auld <matthew.auld@intel.com>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> ---
>   drivers/gpu/drm/i915/i915_gem.c              | 21 +++++++++++++--------
>   drivers/gpu/drm/i915/i915_gem_batch_pool.c   |  4 ++--
>   drivers/gpu/drm/i915/i915_gem_context.c      |  4 ++--
>   drivers/gpu/drm/i915/i915_gem_render_state.c |  7 +++++--
>   drivers/gpu/drm/i915/i915_guc_submission.c   |  2 +-
>   drivers/gpu/drm/i915/intel_display.c         |  4 ++--
>   drivers/gpu/drm/i915/intel_fbdev.c           |  4 ++--
>   drivers/gpu/drm/i915/intel_lrc.c             | 10 ++++++----
>   drivers/gpu/drm/i915/intel_overlay.c         |  2 +-
>   drivers/gpu/drm/i915/intel_ringbuffer.c      | 19 ++++++++++---------
>   10 files changed, 44 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 261a3ef..c6c17dd 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -382,8 +382,8 @@ i915_gem_create(struct drm_file *file,
>
>   	/* Allocate the new object */
>   	obj = i915_gem_alloc_object(dev, size);
> -	if (obj == NULL)
> -		return -ENOMEM;
> +	if (IS_ERR(obj))
> +		return PTR_ERR(obj);
>
>   	ret = drm_gem_handle_create(file, &obj->base, &handle);
>   	/* drop reference from allocate - handle holds it now */
> @@ -4498,15 +4498,15 @@ struct drm_i915_gem_object *i915_gem_alloc_object(struct drm_device *dev,
>   	struct drm_i915_gem_object *obj;
>   	struct address_space *mapping;
>   	gfp_t mask;
> +	int ret;
>
>   	obj = i915_gem_object_alloc(dev);
>   	if (obj == NULL)
> -		return NULL;
> +		return ERR_PTR(-ENOMEM);

The two changes above looked really really confusing, where one tests 
the returned pointer and returns it if it's an ERR_PTR, and the other 
tests for NULL and returns ERR_PTR(-ENOMEM).

Then I realised one was i915_gem_alloc_object() and the other was 
i915_gem_object_alloc()!

Can we please get rid of one or the other? Since we generally use 
subsystem_class_action naming, I'd suggest keeping (the low-level 
memory-allocator) i915_gem_object_alloc(), and renaming the high-level 
i915_gem_alloc_object() to i915_gem_object_create() or similar.

> -	if (drm_gem_object_init(dev, &obj->base, size) != 0) {
> -		i915_gem_object_free(obj);
> -		return NULL;
> -	}
> +	ret = drm_gem_object_init(dev, &obj->base, size);
> +	if (ret)
> +		goto fail;
>
>   	mask = GFP_HIGHUSER | __GFP_RECLAIMABLE;
>   	if (IS_CRESTLINE(dev) || IS_BROADWATER(dev)) {
> @@ -4543,6 +4543,11 @@ struct drm_i915_gem_object *i915_gem_alloc_object(struct drm_device *dev,
>   	trace_i915_gem_object_create(obj);

Oh and BTW i915_gem_alloc_object() already calls itself 
i915_gem_object_create() in trace messages!

.Dave.
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