Re: [PATCH v4] gpu: drm: i915: Change return type to vm_fault_t

[Chris Wilson <chris@chris-wilson.co.uk>]

Quoting Souptick Joarder (2018-05-16 20:12:20)
> Use new return type vm_fault_t for fault handler. For
> now, this is just documenting that the function returns
> a VM_FAULT value rather than an errno. Once all instances
> are converted, vm_fault_t will become a distinct type.
> 
> commit 1c8f422059ae ("mm: change return type to vm_fault_t")
> 
> Fixed one checkpatch.pl warning inside WARN_ONCE.
> 
> Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
> ---

> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index dd89abd..732abdf 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1882,7 +1882,7 @@ int i915_gem_mmap_gtt_version(void)
>   * The current feature set supported by i915_gem_fault() and thus GTT mmaps
>   * is exposed via I915_PARAM_MMAP_GTT_VERSION (see i915_gem_mmap_gtt_version).
>   */
> -int i915_gem_fault(struct vm_fault *vmf)
> +vm_fault_t i915_gem_fault(struct vm_fault *vmf)
>  {
>  #define MIN_CHUNK_PAGES ((1 << 20) >> PAGE_SHIFT) /* 1 MiB */
>         struct vm_area_struct *area = vmf->vma;
> @@ -1894,7 +1894,8 @@ int i915_gem_fault(struct vm_fault *vmf)
>         struct i915_vma *vma;
>         pgoff_t page_offset;
>         unsigned int flags;
> -       int ret;
> +       int err;
> +       vm_fault_t ret = VM_FAULT_SIGBUS;
>  
>         /* We don't use vmf->pgoff since that has the fake offset */
>         page_offset = (vmf->address - area->vm_start) >> PAGE_SHIFT;
> @@ -2027,8 +2028,7 @@ int i915_gem_fault(struct vm_fault *vmf)
>                 ret = VM_FAULT_SIGBUS;
>                 break;
>         default:
> -               WARN_ONCE(ret, "unhandled error in i915_gem_fault: %i\n", ret);
> -               ret = VM_FAULT_SIGBUS;
> +               WARN_ONCE(ret, "unhandled error in %s: %x\n", __func__, err);
>                 break;

Even simpler would be to use e.g. return VM_FAULT_SIGBUS for each case
above. No early initialisation of use-once variables allowing the
compiler to do it's job. For a smaller patch, you can even skip the
s/ret/err/
-Chris
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