Re: [PATCH v2 2/2] mm,nodemask: Use nr_node_ids

[Peter Zijlstra <peterz@infradead.org>]

On Thu, Aug 03, 2023 at 01:41:42PM -0700, Yury Norov wrote:
> Consider MAX_NUMNODES == 64 and nr_node_ids == 4. Then
> small_nodemask_bits == 64.
> 
> The nodes_full() will set all 64 bits:
> 
>   #define nodes_full(nodemask) __nodes_full(&(nodemask), small_nodemask_bits)
>   static inline bool __nodes_full(const nodemask_t *srcp, unsigned int nbits)
>   {
>           return bitmap_full(srcp->bits, nbits);
>   }
> 
> And the following nodes_weight() will return 64:
> 
>   #define nodes_weight(nodemask) __nodes_weight(&(nodemask), small_nodemask_bits)
>   static inline int __nodes_weight(const nodemask_t *srcp, unsigned int nbits)
>   {
>           return bitmap_weight(srcp->bits, nbits);
>   }

That would be a straight up bug. You're asking it: tell me how many of
these 4 bits are set, and they you say: 64. At which point I'll suggest
they go back to primary school and do the counting lessons again.

Hmm?