Re: [PATCH v1] x86/mm/pat: (un)track_pfn_copy() fix + improvements

[Ingo Molnar]

* David Hildenbrand <david@xxxxxxxxxx> wrote:

> We got a late smatch warning and some additional review feedback.
> 
> 	smatch warnings:
> 	mm/memory.c:1428 copy_page_range() error: uninitialized symbol 'pfn'.

> -	if (!(src_vma->vm_flags & VM_PAT))
> +	if (!(src_vma->vm_flags & VM_PAT)) {
> +		*pfn = 0;
>  		return 0;
> +	}

>  static inline int track_pfn_copy(struct vm_area_struct *dst_vma,
>  		struct vm_area_struct *src_vma, unsigned long *pfn)
>  {
> +	*pfn = 0;
>  	return 0;
>  }

That's way too ugly. There's nothing wrong with not touching 'pfn' in 
the error path: in fact it's pretty standard API where output pointers 
may not get set on errors.

If Smatch has a problem with it, Smatch should be fixed, or the false 
positive warning should be worked around by initializing 'pfn' in the 
callers.

Thanks,

	Ingo