linux-kernel - Re: [PATCH 3/3] x86/intel_rdt: Return error for incorrect resource names in schemata

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Date:   Thu, 20 Apr 2017 11:57:13 -0700 (PDT)
From:   Shivappa Vikas <vikas.shivappa@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>
cc:     Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
        vikas.shivappa@...el.com, x86@...nel.org,
        linux-kernel@...r.kernel.org, sai.praneeth.prakhya@...el.com,
        hpa@...or.com, mingo@...nel.org,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>, tony.luck@...el.com,
        "Yu, Fenghua" <fenghua.yu@...el.com>
Subject: Re: [PATCH 3/3] x86/intel_rdt: Return error for incorrect resource
 names in schemata



On Thu, 20 Apr 2017, Thomas Gleixner wrote:

> On Wed, 19 Apr 2017, Vikas Shivappa wrote:
>
>>  		}
>
> The resulting loop is just horrible to read. We can do better than
> that. Patch below.
>
> Thanks,
>
> 	tglx
> 8<-------------
>
> --- a/arch/x86/kernel/cpu/intel_rdt_schemata.c
> +++ b/arch/x86/kernel/cpu/intel_rdt_schemata.c
> @@ -187,6 +187,17 @@ static int update_domains(struct rdt_res
> 	return 0;
> }
>
> +static int rdtgroup_parse_resource(char *resname, char *tok, int closid)
> +{
> +	struct rdt_resource *r;
> +
> +	for_each_enabled_rdt_resource(r) {
> +		if (!strcmp(resname, r->name) && closid < r->num_closid)
> +			return parse_line(tok, r);
> +	}
> +	return -EINVAL;
> +}
> +
> ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
> 				char *buf, size_t nbytes, loff_t off)
> {
> @@ -209,9 +220,10 @@ ssize_t rdtgroup_schemata_write(struct k
>
> 	closid = rdtgrp->closid;
>
> -	for_each_enabled_rdt_resource(r)
> +	for_each_enabled_rdt_resource(r) {
> 		list_for_each_entry(dom, &r->domains, list)
> 			dom->have_new_ctrl = false;
> +	}
>
> 	while ((tok = strsep(&buf, "\n")) != NULL) {
> 		resname = strsep(&tok, ":");
> @@ -219,19 +231,9 @@ ssize_t rdtgroup_schemata_write(struct k
> 			ret = -EINVAL;
> 			goto out;
> 		}
> -		for_each_enabled_rdt_resource(r) {
> -			if (!strcmp(strim(resname), r->name) &&
> -			    closid < r->num_closid) {
> -				ret = parse_line(tok, r);
> -				if (ret)
> -					goto out;
> -				break;
> -			}
> -		}
> -		if (!r->name) {
> -			ret = -EINVAL;
> +		ret = rdtgroup_parse_resource(strim(resname), tok, closid);
> +		if (ret)
> 			goto out;
> -		}
> 	}

Ok agree its better way. I was trying to add a NULL which Tony already said was 
Nacked, did not really want to use a pointer which may be out of bounds 
although we dont check the contents.

Thanks,
Vikas