linux-kernel - Re: [PATCH v2 1/2] selftests/resctrl: Fix schemata write error check

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Message-ID: <tqdf3l4kwkqzdiks2pddtze6xunmqtgogslupvvjyskexfhkdo@dtxmzzegsxt4>
Date:   Mon, 28 Aug 2023 14:55:05 +0200
From:   Maciej Wieczór-Retman 
        <maciej.wieczor-retman@...el.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
CC:     LKML <linux-kernel@...r.kernel.org>,
        <linux-kselftest@...r.kernel.org>, <shuah@...nel.org>,
        <fenghua.yu@...el.com>, Reinette Chatre <reinette.chatre@...el.com>
Subject: Re: [PATCH v2 1/2] selftests/resctrl: Fix schemata write error check

On 2023-08-28 at 13:43:05 +0300, Ilpo Järvinen wrote:
>On Mon, 28 Aug 2023, Wieczor-Retman, Maciej wrote:
>> diff --git a/tools/testing/selftests/resctrl/resctrlfs.c b/tools/testing/selftests/resctrl/resctrlfs.c
>> index bd36ee206602..0f9644e5a25e 100644
>> --- a/tools/testing/selftests/resctrl/resctrlfs.c
>> +++ b/tools/testing/selftests/resctrl/resctrlfs.c
>> @@ -488,9 +488,8 @@ int write_bm_pid_to_resctrl(pid_t bm_pid, char *ctrlgrp, char *mongrp,
>>   */
>>  int write_schemata(char *ctrlgrp, char *schemata, int cpu_no, char *resctrl_val)
>>  {
>> -	char controlgroup[1024], schema[1024], reason[64];
>> -	int resource_id, ret = 0;
>> -	FILE *fp;
>> +	char controlgroup[1024], schema[1024], reason[128];
>> +	int resource_id, fp, ret = 0;
>
>fp -> fd to follow the usual convention.

Okay, I'll change it

>>  
>> -	fp = fopen(controlgroup, "w");
>> +	fp = open(controlgroup, O_WRONLY);
>>  	if (!fp) {
>>  		sprintf(reason, "Failed to open control group");
>>  		ret = -1;
>>  
>>  		goto out;
>>  	}
>> -
>> -	if (fprintf(fp, "%s\n", schema) < 0) {
>> -		sprintf(reason, "Failed to write schemata in control group");
>> -		fclose(fp);
>> +	if (write(fp, schema, strlen(schema)) < 0) {
>
>snprintf() returns you the length, just store the return value and there's 
>no need to calculate it here.

Thanks for the suggestion, tested it and it works fine, I'll add it in
the next version.

>> +		snprintf(reason, sizeof(reason),
>> +			 "write() failed : %s", strerror(errno));
>> +		close(fp);
>>  		ret = -1;
>>  
>>  		goto out;
>>  	}
>> -	fclose(fp);
>> +	close(fp);
>> +	schema[strcspn(schema, "\n")] = 0;
>
>Here too you can use the known length/index instead of strcspr().

Same as above

-- 
Kind regards
Maciej Wieczór-Retman