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Date: Fri, 13 Jun 2014 09:19:12 +0800
From: Qu Wenruo <quwenruo@cn.fujitsu.com>
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To: <dsterba@suse.cz>, <linux-btrfs@vger.kernel.org>
Subject: Re: [PATCH v2] btrfs-progs: Improve the parse_size() error message.
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-------- Original Message --------
Subject: Re: [PATCH v2] btrfs-progs: Improve the parse_size() error message.
From: David Sterba <dsterba@suse.cz>
To: Qu Wenruo <quwenruo@cn.fujitsu.com>
Date: 2014年06月12日 18:15
> On Thu, May 29, 2014 at 09:42:11AM +0800, Qu Wenruo wrote:
>> When using parse_size(), even non-numeric value is passed, it will only
>> give error message "ERROR: size value is empty", which is quite
>> confusing for end users.
>>
>> This patch will introduce more meaningful error message for the
>> following new cases
>> 1) Invalid size string (non-numeric string)
>> 2) Minus size value (like "-1K")
>>
>> Also this patch will take full use of endptr returned by strtoll() to
>> reduce unneeded loop.
>>
>> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
>> ---
>>   utils.c | 56 +++++++++++++++++++++++++++++++++++++++-----------------
>>   1 file changed, 39 insertions(+), 17 deletions(-)
>>
>> diff --git a/utils.c b/utils.c
>> index 392c5cf..499f08f 100644
>> --- a/utils.c
>> +++ b/utils.c
>> @@ -1612,18 +1612,45 @@ scan_again:
>>   
>>   u64 parse_size(char *s)
>>   {
>> -	int i;
>>   	char c;
>> +	char *endptr;
>>   	u64 mult = 1;
>> +	long long int signed_ret;
>> +	u64 ret;
>>   
>> -	for (i = 0; s && s[i] && isdigit(s[i]); i++) ;
>> -	if (!i) {
>> -		fprintf(stderr, "ERROR: size value is empty\n");
>> -		exit(50);
>> +	if (!s) {
>> +		fprintf(stderr, "ERROR: Size value is empty\n");
>> +		exit(1);
> We never pass a NULL pointer to parse_size so this check will be always
> false. Previously it verified that there are at least some digits.
Command like 'mkfs.btrfs -b /dev/sda' *WILL* pass NULL pointer to 
parse_size(), so the check is needed.

>
>>   	}
>> -
>> -	if (s[i]) {
>> -		c = tolower(s[i]);
>> +	signed_ret = strtoll(s, &endptr, 10);
>> +	if (endptr == s) {
>> +		fprintf(stderr, "ERROR: Size value '%s' is invalid\n", s);
>> +		exit(1);
>> +	}
>> +	if (endptr[0] && endptr[1]) {
>> +		fprintf(stderr, "ERROR: Illegal suffix contains character '%c' in wrong position\n",
>> +			endptr[1]);
>> +		exit(1);
>> +	}
>> +	if (signed_ret <= 0) {
>> +		fprintf(stderr,
>> +			"ERROR: Size value '%s' is less equal than 0\n", s);
>> +		exit(1);
>> +	}
>> +	/* strtoll returns LLONG_MAX when overflow, if this happens,
>> +	 * need to call strtoull to get the real size */
>> +	if (errno == ERANGE && signed_ret == LLONG_MAX) {
>> +		ret = strtoull(s, NULL, 10);
> Why do you parse the number twice? Negative sizes are currently not used
> so you can reject them.
I will change the patch to judgement leading '-' and reject the value.
>
>> +		if (errno == ERANGE && ret == ULLONG_MAX) {
>> +			fprintf(stderr,
>> +				"ERROR: Size value '%s' is too large for u64\n",
>> +				s);
>> +			exit(1);
>> +		}
>> +	} else
>> +		ret = signed_ret;
>> +	if (endptr[0]) {
>> +		c = tolower(endptr[0]);
>>   		switch (c) {
>>   		case 'e':
>>   			mult *= 1024;
>> @@ -1646,18 +1673,13 @@ u64 parse_size(char *s)
>>   		case 'b':
>>   			break;
>>   		default:
>> -			fprintf(stderr, "ERROR: Unknown size descriptor "
>> -				"'%c'\n", c);
>> +			fprintf(stderr, "ERROR: Unknown size descriptor '%c'\n", c);
>>   			exit(1);
>>   		}
>>   	}
>> -	if (s[i] && s[i+1]) {
>> -		fprintf(stderr, "ERROR: Illegal suffix contains "
>> -			"character '%c' in wrong position\n",
>> -			s[i+1]);
>> -		exit(51);
>> -	}
>> -	return strtoull(s, NULL, 10) * mult;
>> +
>> +	ret *= mult;
> Although there was no overflow check before, I think it should be here.
> Eg. 12345678P is a valid size string but the result does not fit u64.
Right, I will check the overflow here.

Thanks,
Qu
>
>> +	return ret;
>>   }