Re: [PATCH net-next v3] net: preserve rps_default_mask on failed writes

[Wang Zhan]

On Sun, 08 Nov 2026 13:19:12 +0000 Yingjie Wang wrote:
Two nits, if you happen to respin:

> @@ -105,34 +105,36 @@ static int rps_default_mask_sysctl(const struct ctl_table *table, int write,
>  				   void *buffer, size_t *lenp, loff_t *ppos)
>  {
>  	struct net *net = (struct net *)table->data;
> +	struct cpumask *new_mask = NULL;
>  	struct cpumask *mask;
>  	int err = 0;
>  
> -	mutex_lock(&rps_default_mask_mutex);
> -	mask = net->core.rps_default_mask;
>  	if (write) {
> -		if (!mask) {
> -			mask = kzalloc(cpumask_size(), GFP_KERNEL);
> -			net->core.rps_default_mask = mask;
> -		}
> -		err = -ENOMEM;
> -		if (!mask)
> -			goto done;
> +		new_mask = kzalloc(cpumask_size(), GFP_KERNEL);
> +		if (!new_mask)
> +			return -ENOMEM;
>  
> -		err = cpumask_parse(buffer, mask);
> +		err = cpumask_parse(buffer, new_mask);
>  		if (err)
> -			goto done;
> +			goto out;
>  
> -		err = rps_cpumask_housekeeping(mask);
> +		err = rps_cpumask_housekeeping(new_mask);
>  		if (err)
> -			goto done;
> +			goto out;
> +	}
> +
> +	mutex_lock(&rps_default_mask_mutex);
> +	mask = net->core.rps_default_mask;

nit: use net->core.rps_default_mask directly in the read path and drop
the variable; there are no other users.

> @@ -105,34 +105,36 @@ static int rps_default_mask_sysctl(const struct ctl_table *table, int write,
>  				   void *buffer, size_t *lenp, loff_t *ppos)
>  {
>  	struct net *net = (struct net *)table->data;
> +	struct cpumask *new_mask = NULL;
>  	struct cpumask *mask;
>  	int err = 0;
>  
> -	mutex_lock(&rps_default_mask_mutex);
> -	mask = net->core.rps_default_mask;
>  	if (write) {
> -		if (!mask) {
> -			mask = kzalloc(cpumask_size(), GFP_KERNEL);
> -			net->core.rps_default_mask = mask;
> -		}
> -		err = -ENOMEM;
> -		if (!mask)
> -			goto done;
> +		new_mask = kzalloc(cpumask_size(), GFP_KERNEL);
> +		if (!new_mask)
> +			return -ENOMEM;
>  
> -		err = cpumask_parse(buffer, mask);
> +		err = cpumask_parse(buffer, new_mask);
>  		if (err)
> -			goto done;
> +			goto out;
>  
> -		err = rps_cpumask_housekeeping(mask);
> +		err = rps_cpumask_housekeeping(new_mask);
>  		if (err)
> -			goto done;
> +			goto out;
> +	}
> +
> +	mutex_lock(&rps_default_mask_mutex);
> +	mask = net->core.rps_default_mask;
> +	if (write) {
> +		swap(net->core.rps_default_mask, new_mask);
>  	} else {
>  		err = dump_cpumask(buffer, lenp, ppos,
>  				   mask ?: cpu_none_mask);
>  	}
>  
> -done:
>  	mutex_unlock(&rps_default_mask_mutex);

nit: move this up to the closing brace and add a blank line before out:, so
the unlock is visibly paired with the lock.

Thanks