Re: [PATCH v2 2/2] mm: attempt to batch free swap entries for zap_pte_range()

[David Hildenbrand]

> > > +     if (!has_cache) {
> > > +             spin_lock(&si->lock);
> >
> > I'm no expert on that code, but we might drop the cluster lock the take
> > the swap_info lock and then retake the cluster lock. I assume there are
> > no races we are worrying about here, right?
>
> I suppose so. Even the original single-entry code follows the same pattern:
>
> static unsigned char __swap_entry_free(struct swap_info_struct *p,
>         swp_entry_t entry)
> {
>           struct swap_cluster_info *ci;
>           unsigned long offset = swp_offset(entry);
>           unsigned char usage;
>
>           ci = lock_cluster_or_swap_info(p, offset);
>           usage = __swap_entry_free_locked(p, offset, 1);
>           unlock_cluster_or_swap_info(p, ci);
>           if (!usage)
>                    free_swap_slot(entry);
>
>           return usage;
> }
>
> I assume that once we mark them as SWAP_HAS_CACHE, no one else
> will touch them except ourselves.

That makes sense, thanks!

--
Cheers,

David / dhildenb