Re: [PATCH] mm/migrate: fix deadlock in migrate_pages_batch() on large folios

[Gao Xiang]

On 2024/8/16 13:12, Gao Xiang wrote:
> Hi Andrew,
>
> On 2024/8/16 13:02, Andrew Morton wrote:
> > On Mon, 29 Jul 2024 09:58:02 +0800 Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx> wrote:
> >
> > > > For the fix, I think that we should still respect migrate_mode because
> > > > users may prefer migration success over blocking.
> > > >
> > > > @@ -1492,11 +1492,17 @@ static int unmap_and_move_huge_page(new_folio_t get_new_folio,
> > > >        return rc;
> > > >    }
> > > > -static inline int try_split_folio(struct folio *folio, struct list_head *split_folios)
> > > > +static inline int try_split_folio(struct folio *folio, struct list_head *split_folios,
> > > > +                  enum migrate_mode mode)
> > > >    {
> > > >        int rc;
> > > > -    folio_lock(folio);
> > > > +    if (mode == MIGRATE_ASYNC) {
> > > > +        if (!folio_trylock(folio))
> > > > +            return -EAGAIN;
> > > > +    } else {
> > > > +        folio_lock(folio);
> > > > +    }
> > > >        rc = split_folio_to_list(folio, split_folios);
> > > >        folio_unlock(folio);
> > > >        if (!rc)
> > >
> > > Okay, yeah it looks better since it seems I missed the fallback
> > > part in migrate_pages_sync().
> > >
> > > Let me send the next version to follow your advice, thanks.
> >
> > The author seems to have disappeared.  Should we merge this as-is or
> > does someone want to take a look at developing a v2?
>
> I've replied your email last week, I'm not sure why it has not
> been addressed?
>
> https://lore.kernel.org/linux-mm/20240729021306.398286-1-hsiangkao@xxxxxxxxxxxxxxxxx/
>
> The patch in your queue is already v2? No?

Really confused about this, since the comment above was about v1.
and v2 is already sent (in July 29) and in -next for two weeks
with

Reviewed-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>

What else I need to do to resolve this already resolved comment
so that I could enable large folios without deadlocks anymore?

Thanks,
Gao Xiang

> Thanks,
> Gao Xiang