Re: [PATCH] mm/migrate: fix deadlock in migrate_pages_batch() on large folios
From: Andrew Morton
Date: Fri Aug 16 2024 - 01:02:32 EST
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?
Thanks.