Re: [PATCH 2/5] mm/memory_hotplug: Avoid node_set/clear_state(N_HIGH_MEMORY) when !CONFIG_HIGHMEM

[Pasha Tatashin]

On 9/19/18 6:08 AM, Oscar Salvador wrote:
> From: Oscar Salvador <osalvador@xxxxxxx>
> 
> Currently, when !CONFIG_HIGHMEM, status_change_nid_high is being set
> to status_change_nid_normal, but on such systems N_HIGH_MEMORY falls
> back to N_NORMAL_MEMORY.
> That means that if status_change_nid_normal is not -1,
> we will perform two calls to node_set_state for the same memory type.
> 
> Set status_change_nid_high to -1 for !CONFIG_HIGHMEM, so we skip the
> double call in node_states_set_node.
> 
> The same goes for node_clear_state.
> 
> Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>

Reviewed-by: Pavel Tatashin <pavel.tatashin@xxxxxxxxxxxxx>

This is a rare case where I think comments are unnecessary as the code
is self explanatory. So, I would remove the comments before:

> +	arg->status_change_nid_high = -1;

Pavel

> ---
>  mm/memory_hotplug.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 63facfc57224..c2c7359bd0a7 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -731,7 +731,11 @@ static void node_states_check_changes_online(unsigned long nr_pages,
>  	else
>  		arg->status_change_nid_high = -1;
>  #else
> -	arg->status_change_nid_high = arg->status_change_nid_normal;
> +	/*
> +	 * When !CONFIG_HIGHMEM, N_HIGH_MEMORY equals N_NORMAL_MEMORY
> +	 * so setting the node for N_NORMAL_MEMORY is enough.
> +	 */
> +	arg->status_change_nid_high = -1;
>  #endif
>  
>  	/*
> @@ -1555,7 +1559,11 @@ static void node_states_check_changes_offline(unsigned long nr_pages,
>  	else
>  		arg->status_change_nid_high = -1;
>  #else
> -	arg->status_change_nid_high = arg->status_change_nid_normal;
> +	/*
> +	 * When !CONFIG_HIGHMEM, N_HIGH_MEMORY equals N_NORMAL_MEMORY
> +	 * so clearing the node for N_NORMAL_MEMORY is enough.
> +	 */
> +	arg->status_change_nid_high = -1;
>  #endif
>  
>  	/*
>