Re: [PATCH v2 1/2] mm: introduce memalloc_flags_move() for transferring allocation scopes

[Zhou, Yun]

On 7/20/26 04:57, Andrew Morton wrote:
> On Sun, 19 Jul 2026 17:57:31 +0800 Yun Zhou <yun.zhou@xxxxxxxxxxxxx> wrote:
>
> > Add memalloc_flags_move() to transfer a saved memalloc scope from one
> > tracking variable to another.  The source is zeroed so that a
> > subsequent memalloc_flags_restore() on it becomes a no-op, effectively
> > transferring ownership of the scope to the destination.
> >
> > This is needed when a subsystem hands off an allocation context from
> > one structure to another (e.g. during transaction rolling in
> > filesystems), and needs to ensure the scope remains active without an
> > extra save/restore cycle.
> >
> > ...
>
> Thanks.  fyi, Sashiko might have found a pre-existing xfs issue:
>          https://sashiko.dev/#/patchset/20260719095732.1813590-1-yun.zhou@xxxxxxxxxxxxx

Good catch. This is indeed a pre-existing issue, and needs a separate fix.

> >   include/linux/sched/mm.h | 17 +++++++++++++++++
> >   1 file changed, 17 insertions(+)
>
> This file isn't mentioned in MAINTAINERS.  Could someone please propose
> a patch?
>
>  From the MM side, probably just place it in every record which mentions
> include/linux/mm.h - close enough.
>
> > --- a/include/linux/sched/mm.h
> > +++ b/include/linux/sched/mm.h
> > @@ -342,6 +342,23 @@ static inline void memalloc_flags_restore(unsigned flags)
> >        current->flags &= ~flags;
> >   }
> >
> > +/**
> > + * memalloc_flags_move - transfer a memalloc scope from one tracking
> > + * variable to another.
> > + * @old_flags: pointer to the source flags (will be zeroed)
> > + *
> > + * Returns the flags value to store in the destination.  The source is
> > + * set to zero so that a subsequent memalloc_flags_restore() on it is
> > + * a no-op.
> > + */
> > +static inline unsigned int memalloc_flags_move(unsigned int *old_flags)
> > +{
> > +     unsigned int ret = *old_flags;
> > +
> > +     *old_flags = 0;
> > +     return ret;
> > +}
> > +
>
> I've added linux-mm to cc here.  Please include it in any future
> versions of this patchset.

Well, got it.

Thanks,
Yun