Re: [PATCH v2] mm: release private data before split THP

[Yang Shi <shy828301@gmail.com>]

On Tue, Aug 9, 2022 at 2:08 AM Aaron Lu <aaron.lu@intel.com> wrote:
>
> On Tue, Aug 09, 2022 at 09:12:57AM +0800, Yin Fengwei wrote:
> > Hi Yang,
> >
> > On 2022/8/9 01:49, Yang Shi wrote:
> > > The GFP_KERNEL is fine for most THP split callsites except for the
> > > memory reclaim path since it might not allow certain flags to avoid
> > > recursion, for example, nested reclaim, issue I/O, etc. The most
> > > filesystems clear __GFP_FS. However it should not be a real life
> > > problem now since AFAIK just xfs supports large folios for now and xfs
> > > uses iomap release_folio() method which actually ignores gfp flags.
> > Thanks a lot for the valuable comments.
> >
> >
> > >
> > > So it sounds safer to follow the gfp convention used by
> > > xas_split_alloc() in the below. The best way is to pass in the gfp
> > > flag from the reclaimer IMO, but it seems overkilling at the moment.
> >
> > It's possible that the gfp used by xas_split_alloc has __GFP_FS/IO set.
> > What about to use current_gfp_context(gfp_as_xas_split_alloc)?
> >
>
> Sounds reasonable to me.
>
> Also, the gfp used by xas_split_alloc() should also be modified to:
> current_gfp_context(mapping_gfp_mask(mapping) & GFP_RECLAIM_MASK)?
> Since they are in the same context.

Good point, fine to me.