Re: [patch v2] mm, pcp: allow restoring percpu_pagelist_fraction default

[Oleg Drokin <green@linuxhacker.ru>]

Hello!

On Jun 4, 2014, at 8:34 PM, David Rientjes wrote:
> @@ -5850,23 +5851,39 @@ int percpu_pagelist_fraction_sysctl_handler(ctl_table *table, int write,
> 	void __user *buffer, size_t *length, loff_t *ppos)
> {
> 	struct zone *zone;
> -	unsigned int cpu;
> +	int old_percpu_pagelist_fraction;
> 	int ret;
> 
> +	mutex_lock(&pcp_batch_high_lock);
> +	old_percpu_pagelist_fraction = percpu_pagelist_fraction;
> +
> 	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
> -	if (!write || (ret < 0))
> -		return ret;
> +	if (!write || ret < 0)
> +		goto out;
> +
> +	/* Sanity checking to avoid pcp imbalance */
> +	if (percpu_pagelist_fraction &&
> +	    percpu_pagelist_fraction < MIN_PERCPU_PAGELIST_FRACTION) {
> +		percpu_pagelist_fraction = old_percpu_pagelist_fraction;
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	ret = 0;

Minor nitpick I guess, but ret cannot be anything but 0 here I think (until somebody changes the way proc_dointvec_minmax for write=true operates)?

The patch is good otherwise.

Thanks.