Re: [PATCH 01/16] mm: use untagged_addr() for get_user_pages_fast addresses

[Christoph Hellwig]

On Fri, Jun 21, 2019 at 10:39:11AM -0300, Jason Gunthorpe wrote:
> Hmm, this function, and the other, goes on to do:
> 
>         if (unlikely(!access_ok((void __user *)start, len)))
>                 return 0;
> 
> and I thought that access_ok takes in the tagged pointer?
> 
> How about re-order it a bit?

Actually..  I we reorder this we'd need to to duplicate a few things
due to the zero/negative length checking.  Given the feedback from
Khalid I'd thus rather skip the reorder for now.  If we have a good
reason we could add it back, but it would be a bit involved.