Re: [PATCH v3 2/3] userfaultfd: UFFDIO_MOVE uABI

[David Hildenbrand]

On 23.10.23 14:29, David Hildenbrand wrote:
> > +
> > +	/* Only allow remapping if both are mlocked or both aren't */
> > +	if ((src_vma->vm_flags & VM_LOCKED) != (dst_vma->vm_flags & VM_LOCKED))
> > +		return -EINVAL;
> > +
> > +	if (!(src_vma->vm_flags & VM_WRITE) || !(dst_vma->vm_flags & VM_WRITE))
> > +		return -EINVAL;
>
> Why does one of both need VM_WRITE? If one really needs it, then the
> destination (where we're moving stuff to).

Just realized that we want both to be writable.

If you have this in place, there is no need to use maybe*_mkwrite(), you 
can use the non-maybe variants.

I recall that for UFFDIO_COPY we even support PROT_NONE VMAs, is there 
any reason why we want to have different semantics here?

--
Cheers,

David / dhildenb