Re: [PATCH] mm/mempolicy: Fix sleeping allocation in alloc_pages_bulk_weighted_interleave()

On Fri, Aug 21, 2026 at 10:40:43AM -0700, Andrew Morton wrote:
> > --- a/mm/mempolicy.c
> > +++ b/mm/mempolicy.c
> > @@ -2688,7 +2688,7 @@ static unsigned long alloc_pages_bulk_weighted_interleave(gfp_t gfp,
> >  	prev_node = node;
> >  
> >  	/* create a local copy of node weights to operate on outside rcu */
> > -	weights = kzalloc(nr_node_ids, GFP_KERNEL);
> > +	weights = kmalloc(nr_node_ids, gfp & GFP_RECLAIM_MASK);
> 
> I wonder if we *really* need the local copy of state->iw_table. 
> Perhaps with appropriate care we can directly use state->iw_table in
> here.
> 
> How much would it hurt to expand the rcu_read_lock() coverage?
> 

Ah, the current space we'd expand rcu read lock into is the actual
allocation - which we can't do. Same with the spinlock.

We can clean this up with a refcount + rcu_free and kill the allocation
in the hot path.  Will get something out this week.

~Gregory