Re: Weird code with change "mm/gup: clean up follow_pfn_pte() slightly"

[Jason Gunthorpe]

On Thu, Feb 03, 2022 at 12:38:33AM -0800, John Hubbard wrote:
> On 2/2/22 22:27, Lukas Bulwahn wrote:
> > Dear John,
> > 
> > Your change "mm/gup: clean up follow_pfn_pte() slightly" (see Link),
> > visible in linux-next as commit 05fef840b5c6 ("mm/gup: clean up
> > follow_pfn_pte() slightly"), is somehow weird.
> 
> Well. That sounds like something to be avoided. :)
> 
> > 
> > In the new branch if (pages), you set page = ERR_PTR(-EFAULT) and goto
> > out. However, at the label out, the value of page is not used, but the
> > return uses the variables i and ret.
> 
> Yes, I think that the complaint is accurate. The intent of this code is
> to return either number of pages so far (i) or ret (which should be zero
> in this case), because we are just stopping early, rather than calling
> this an actual error.

IIRC GUP shouldn't return 0, it should return an error code, not zero.

Jason