linux-kernel - Re: [PATCH 1/2] nodemask: Introduce for_each_node_mask_from/for_each_node_state

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Message-ID: <Z0Z0omMh5f07xv8H@yury-ThinkPad>
Date: Tue, 26 Nov 2024 17:23:46 -0800
From: Yury Norov <yury.norov@...il.com>
To: Andrea Righi <arighi@...dia.com>
Cc: Tejun Heo <tj@...nel.org>, David Vernet <void@...ifault.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] nodemask: Introduce
 for_each_node_mask_from/for_each_node_state_from()

On Tue, Nov 26, 2024 at 10:56:39AM +0100, Andrea Righi wrote:
> Introduce NUMA node iterators to support circular iteration, starting
> from a specified node.

We have a special suffix for circular iterators - "wrap".

> Signed-off-by: Andrea Righi <arighi@...dia.com>
> ---
>  include/linux/nodemask.h | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
> index b61438313a73..35f1fcdd6a84 100644
> --- a/include/linux/nodemask.h
> +++ b/include/linux/nodemask.h
> @@ -392,6 +392,21 @@ static inline void __nodes_fold(nodemask_t *dstp, const nodemask_t *origp,
>  	for ((node) = 0; (node) < 1 && !nodes_empty(mask); (node)++)
>  #endif /* MAX_NUMNODES */
>  
> +#if MAX_NUMNODES > 1
> +#define for_each_node_mask_from(node, mask, start, cnt)			\

You can just use for_each_set_bit_wrap() here, and avoid this ugly
'cnt' in the interface.

 #define for_each_node_mask_wrap(node, nodemask, start)			\
        for_each_set_bit_wrap((node), (nodemask)->bits, (start))

(not tested though)

Thanks,
Yury

> +	for ((node) = (start), (cnt) = 0;				\
> +	     (cnt) == 0 || (node) != (start);				\
> +	     (cnt)++, (node) =						\
> +			next_node((node), (mask)) >= MAX_NUMNODES ?	\
> +				first_node(mask) :			\
> +				next_node((node), (mask)))
> +#else /* MAX_NUMNODES == 1 */
> +#define for_each_node_mask_from(node, mask, start, cnt)			\
> +	for ((node) = 0;						\
> +	     (node) < 1 && !nodes_empty(mask);				\
> +	     (node)++, (void)(start), (void)(cnt))
> +#endif /* MAX_NUMNODES */
> +
>  /*
>   * Bitmasks that are kept for all the nodes.
>   */
> @@ -441,6 +456,9 @@ static inline int num_node_state(enum node_states state)
>  #define for_each_node_state(__node, __state) \
>  	for_each_node_mask((__node), node_states[__state])
>  
> +#define for_each_node_state_from(__node, __state, __start, __cnt) \
> +	for_each_node_mask_from((__node), node_states[__state], __start, __cnt)
> +
>  #define first_online_node	first_node(node_states[N_ONLINE])
>  #define first_memory_node	first_node(node_states[N_MEMORY])
>  static inline unsigned int next_online_node(int nid)
> -- 
> 2.47.0