Re: [PATCH v3 2/3] mm: swap: drop dropbehind swap cache folios on writeback completion

[Alexandre Ghiti]

Hi Matthew,

On Thu, Aug 20, 2026 at 5:42 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
>
> >
> On Thu, Aug 20, 2026 at 07:36:42PM +0800, Barry Song wrote:
> > > +void swap_writeback_dropbehind_folio(struct folio *folio)
> > > +{
> > > +       llist_add((struct llist_node *)&folio->lru,
> > > +                 raw_cpu_ptr(&swap_dropbehind_llist));
> > > +       queue_work(swap_dropbehind_wq, &swap_dropbehind_work);
> > > +}
> > > +
> >
> > This is good. For file dropbehind, I see both F2FS [1] and block
> > devices [2] reinventing workqueues in their own filesystems or
> > drivers, while folio_end_dropbehind() simply benefits from its safe,
> > sleepable context. This seems a bit odd.
> >
> > So I'm really curious whether this could be extended to file-backed
> > folios as well, so that those filesystems and device drivers don't
> > have to deal with this themselves.
>
> You should probably both be aware of Tal's series:
>
> https://lore.kernel.org/linux-mm/20260730-blk-dontcache-v7-0-3e8e6850068d@xxxxxxxxxxxx/
>
> In fact, I'd base this series on Tal's.  It would be considerably
> easier.

At first sight, it seems so, yes. I'm looking into it more deeply
right now, thanks for letting me know!

Thanks,

Alex

>