Re: [PATCH v3 2/3] mm: move folio LRU code out of swap

[Lorenzo Stoakes <ljs@kernel.org>]

On Wed, Jun 03, 2026 at 08:29:44PM +0800, Jianyue Wu wrote:
> On Wed, Jun 3, 2026 at 8:03 PM Lorenzo Stoakes <ljs@kernel.org> wrote:
> >
> > On Wed, Jun 03, 2026 at 06:49:16PM +0800, Baoquan He wrote:
> > > On 06/02/26 at 04:57pm, Matthew Wilcox wrote:
> > > > On Tue, Jun 02, 2026 at 09:01:16AM +0800, Jianyue Wu wrote:
> > > > > Rename mm/swap.c to mm/folio_lru.c so the filename better matches
> > > > > the code's main responsibility.
> > > > >
> > > > > This keeps the implementation split from swap-specific code without
> > > > > changing the published LRU helper interfaces.
> > > >
> > > > At the same time, we have Tal trying to split folio_wait.c out
> > > > of filemap.c.  https://lore.kernel.org/linux-mm/20260520-filemap-split-v1-0-c36ddc2b6cf2@columbia.edu/
> > > >
> > > > I wonder if instead of folio_lru.c and folio_wait.c, we shouldn't simply
> > > > have folio.c.  Tal has 700 lines in his diffstat, you'll have about 1100
> > > > lines, so that's about 1800 llines which seems like a good size.
> > > > There's some functions from mm/util.c that would fit nicely too --
> > > > folio_mapping(), folio_anon_vma(), folio_copy(), flush_dcache_folio()
> > >
> > > I think folio_lru.c and folio_wait.c are better than a single folio.c.
> > >
> > > A single folio.c with all of them would have no clear boundary for what
> > > belongs there and what doesn't. For comparison, page_alloc.c isn't called
> > > page.c (we have files called mm/page*.c).
> >
> > Well page_alloc.c doesn't only contain things that operate on struct page *
> > right?
> >
> > Whereas folio.c is strictly operations literally performed on folios which seems
> > like a good match to me.
> >
> > I find folio_lru.c and folio_wait.c far more difficult to figure out what goes
> > where and there'll be a bunch of miscellaneous stuff all over the place.
> >
> > I vote for folio.c.
> >
> > >
> > > >
> > > > Other people have thoughts?
> > > >
> >
> > Thanks, Lorenzo
>
> Thanks Matthew, Baoquan and Lorenzo for the naming discussion.
>
> I'm posting v4 shortly. It keeps the rename to mm/folio_lru.c so this
> series stays a small cleanup on top of the swap_ops work. A broader
> mm/folio.c (together with Tal's folio_wait split and the util.c
> helpers Matthew mentioned) will be a separate follow-up
> once there is maintainer consensus on the file boundaries.

Agreed! :) Let's get this in first.

>
> Happy to help on that follow-up.

Thanks!

>
> Thanks,
> Best regards,
> Jianyue

Cheers, Lorenzo