Re: [PATCH 3/5] mm: Rework return value for copy_one_pte()

Oleg Nesterov
2020-09-22T10:18:35Z

On 09/22, Oleg Nesterov wrote:
>
> On 09/21, Peter Xu wrote:
> >
> > @@ -866,13 +877,18 @@ static int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
> > pte_unmap_unlock(orig_dst_pte, dst_ptl);
> > cond_resched();
> >
> > - if (entry.val) {
> > - if (add_swap_count_continuation(entry, GFP_KERNEL) < 0)
> > + switch (copy_ret) {
> > + case COPY_MM_SWAP_CONT:
> > + if (add_swap_count_continuation(data.entry, GFP_KERNEL) < 0)
> > return -ENOMEM;
> > - progress = 0;
> > + break;
>
> Note that you didn't clear copy_ret, it is still COPY_MM_SWAP_CONT,
>
> > + default:
> > + break;
> > }
> > +
> > if (addr != end)
> > goto again;
>
> After that the main loop can stop again because of need_resched(), and
> in this case add_swap_count_continuation(data.entry) will be called again?

No, this is not possible, copy_one_pte() should be called at least once,
progress = 0 before restart. Sorry for noise.

Oleg.