Re: [PATCH 1/2] mm: page_alloc: do not give all non-blocking requests reserve access

[Johannes Weiner]

On Mon, Sep 21, 2026 at 03:54:32PM +0100, Matthew Wilcox wrote:
> On Mon, Sep 21, 2026 at 10:38:18AM -0400, Johannes Weiner wrote:
> > +++ b/mm/page_alloc.c
> > @@ -3246,7 +3246,9 @@ struct page *rmqueue_buddy(struct zone *preferred_zone, struct zone *zone,
> >  			 * reserves as failing now is worse than failing a
> >  			 * high-order atomic allocation in the future.
> >  			 */
> > -			if (!page && (alloc_flags & (ALLOC_OOM|ALLOC_NON_BLOCK)))
> > +			if (!page &&
> > +			    ((alloc_flags & ALLOC_OOM) ||
> > +			     (alloc_flags & ALLOC_MASK_ATOMIC) == ALLOC_MASK_ATOMIC))
> >  				page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
> 
> Would this be slightly neater?
> 
> static inline bool may_access_reserves(unsigned int alloc_flags)
> {
> 	if (alloc_flags & ALLOC_OOM)
> 		return true;
> 	if (alloc_flags & (ALLOC_NON_BLOCK | ALLOC_MIN_RESERVE)) ==
> 	    (ALLOC_NON_BLOCK | ALLOC_MIN_RESERVE)
> 		return true;
> 	return false;
> }

I tend to be hesitant with single-use abstractions, but no objection
if people think this is better.