Re: [PATCH] powerpc: platform: cell: spufs: Change return type to vm_fault_t

[Matthew Wilcox <willy@infradead.org>]

On Wed, Apr 18, 2018 at 12:50:38AM +0530, Souptick Joarder wrote:
> 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.
> 
> Reference id -> 1c8f422059ae ("mm: change return type to
> vm_fault_t")
> 
> Previously vm_insert_pfn() returns err but driver returns 
> VM_FAULT_NOPAGE as default. The new function vmf_insert_pfn()
> will replace this inefficiency by returning correct VM_FAULT_*
> type.
> 
> vmf_handle_error is a inline wrapper function which
> will convert error number to vm_fault_t type err.

I think you sent the wrong version of this one ...

The commit message should mention that we're fixing a minor bug, that
the error from vm_insert_pfn() was being ignored and the effect of this
is likely to be only felt in OOM situations.

> @@ -256,11 +257,11 @@ static ssize_t spufs_attr_write(struct file *file, const char __user *buf,
>  		vma->vm_page_prot = pgprot_noncached_wc(vma->vm_page_prot);
>  		pfn = (ctx->spu->local_store_phys + offset) >> PAGE_SHIFT;
>  	}
> -	vm_insert_pfn(vma, vmf->address, pfn);
> +	ret = vmf_insert_pfn(vma, vmf->address, pfn);
>  
>  	spu_release(ctx);
>  
> -	return VM_FAULT_NOPAGE;
> +	return ret;
>  }

I thought I said not to introduce vmf_handle_error(), because it's too
trivial and obfuscates what's actually going on.

> -static int spufs_ps_fault(struct vm_fault *vmf,
> +static inline vm_fault_t vmf_handle_error(int err)
> +{
> +	return VM_FAULT_NOPAGE;
> +}
> +

Re-reading spufs_ps_fault(), I wouldn't change anything inside it.  Just
change its return type to vm_fault_t and call it done.