Re: [PATCH v4 08/23] vfio, mm: fix get_user_pages_remote() and FOLL_LONGTERM

[John Hubbard]

On 11/13/19 11:17 AM, Ira Weiny wrote:
...
> > > @@ -348,33 +347,13 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr,
> > >   		flags |= FOLL_WRITE;
> > >   
> > >   	down_read(&mm->mmap_sem);
> > > -	if (mm == current->mm) {
> > > -		ret = get_user_pages(vaddr, 1, flags | FOLL_LONGTERM, page,
> > > -				     vmas);
> > > -	} else {
> > > -		ret = get_user_pages_remote(NULL, mm, vaddr, 1, flags, page,
> > > -					    vmas, NULL);
> > > -		/*
> > > -		 * The lifetime of a vaddr_get_pfn() page pin is
> > > -		 * userspace-controlled. In the fs-dax case this could
> > > -		 * lead to indefinite stalls in filesystem operations.
> > > -		 * Disallow attempts to pin fs-dax pages via this
> > > -		 * interface.
> > > -		 */
> > > -		if (ret > 0 && vma_is_fsdax(vmas[0])) {
> > > -			ret = -EOPNOTSUPP;
> > > -			put_page(page[0]);
> > > -		}
> > > -	}
> > > -	up_read(&mm->mmap_sem);
> > > -
> > > +	ret = get_user_pages_remote(NULL, mm, vaddr, 1, flags | FOLL_LONGTERM,
> > > +				    page, NULL, NULL);
> > >   	if (ret == 1) {
> > >   		*pfn = page_to_pfn(page[0]);
> > >   		return 0;
> >
> > Mind the return with the lock held this needs some goto unwind
>
> Ah yea...  retract my reviewed by...  :-(

ooops, embarrassed that I missed that, good catch. Will repost with it fixed.



thanks,
--
John Hubbard
NVIDIA