Re: [PATCH] drm/i915: tidy up gen8_init_scratch

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

On ti, 2016-04-26 at 10:27 +0100, Matthew Auld wrote:
> Use goto teardown path and also ensure we reset any struct members which
> would otherwise contain an error encoded pointer, and could be mistaken
> for a valid address.
> 
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Signed-off-by: Matthew Auld <matthew.auld@intel.com>

As this goes through the whole function, good idea to check with git
blame for the function author and CC (in this case Mika, added as CC).

> ---
>  drivers/gpu/drm/i915/i915_gem_gtt.c | 36 +++++++++++++++++++++++++-----------
>  1 file changed, 25 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index 0d666b3..a723b74 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -866,31 +866,31 @@ static void gen8_free_page_tables(struct drm_device *dev,
>  static int gen8_init_scratch(struct i915_address_space *vm)
>  {
>  	struct drm_device *dev = vm->dev;
> +	int ret;
>  
>  	vm->scratch_page = alloc_scratch_page(dev);
> -	if (IS_ERR(vm->scratch_page))
> -		return PTR_ERR(vm->scratch_page);
> +	if (IS_ERR(vm->scratch_page)) {
> +		ret = PTR_ERR(vm->scratch_page);
> +		goto fail_scratch;
> +	}
>  
>  	vm->scratch_pt = alloc_pt(dev);
>  	if (IS_ERR(vm->scratch_pt)) {
> -		free_scratch_page(dev, vm->scratch_page);
> -		return PTR_ERR(vm->scratch_pt);
> +		ret = PTR_ERR(vm->scratch_pt);
> +		goto fail_pt;
>  	}
>  
>  	vm->scratch_pd = alloc_pd(dev);
>  	if (IS_ERR(vm->scratch_pd)) {
> -		free_pt(dev, vm->scratch_pt);
> -		free_scratch_page(dev, vm->scratch_page);
> -		return PTR_ERR(vm->scratch_pd);
> +		ret = PTR_ERR(vm->scratch_pd);
> +		goto fail_pd;
>  	}
>  
>  	if (USES_FULL_48BIT_PPGTT(dev)) {
>  		vm->scratch_pdp = alloc_pdp(dev);
>  		if (IS_ERR(vm->scratch_pdp)) {
> -			free_pd(dev, vm->scratch_pd);
> -			free_pt(dev, vm->scratch_pt);
> -			free_scratch_page(dev, vm->scratch_page);
> -			return PTR_ERR(vm->scratch_pdp);
> +			ret = PTR_ERR(vm->scratch_pdp);
> +			goto fail_pdp;
>  		}
>  	}
>  
> @@ -900,6 +900,20 @@ static int gen8_init_scratch(struct i915_address_space *vm)
>  		gen8_initialize_pdp(vm, vm->scratch_pdp);
>  
>  	return 0;
> +
> +fail_pdp:
> +	vm->scratch_pdp = NULL;

I don't think assigning to NULL is necessary. If this function fails,
it'll lead to driver init failure.

> +	free_pd(dev, vm->scratch_pd);
> +fail_pd:
> +	vm->scratch_pd = NULL;
> +	free_pt(dev, vm->scratch_pt);
> +fail_pt:
> +	vm->scratch_pt = NULL;
> +	free_scratch_page(dev, vm->scratch_page);
> +fail_scratch:
> +	vm->scratch_page = NULL;
> +

Same comment as in the last patch, related to labels, the label should
describe the code under goto section, not the code/situation that jumps
to it.

Regards, Joonas

> +	return ret;
>  }
>  
>  static int gen8_ppgtt_notify_vgt(struct i915_hw_ppgtt *ppgtt, bool create)
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
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