linux-ext4 - Re: [PATCH v4] debugfs/logdump.c: Add parameter t to dump sequence commit timestamps

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Message-ID: <20cb25f6-add9-8944-3138-92f95c8b0d45@huawei.com>
Date: Sat, 5 Jul 2025 08:39:51 +0800
From: zhanchengbin <zhanchengbin1@...wei.com>
To: "Darrick J. Wong" <djwong@...nel.org>
CC: Theodore Ts'o <tytso@....edu>, <linux-ext4@...r.kernel.org>,
	<qiangxiaojun@...wei.com>, <hejie3@...wei.com>
Subject: Re: [PATCH v4] debugfs/logdump.c: Add parameter t to dump sequence
 commit timestamps

On 2025/7/4 11:33, Darrick J. Wong worte:
> On Fri, Jul 04, 2025 at 10:11:09AM +0800, zhanchengbin wrote:
>> On 2025/7/3 23:39, Darrick J. Wong wrote:
>>> On Thu, Jul 03, 2025 at 08:07:53PM +0800, zhanchengbin wrote:
>>>>
>>>> +static void dump_commit_time(FILE *out_file, char *buf)
>>>> +{
>>>> +	struct commit_header	*header;
>>>> +	uint64_t	commit_sec;
>>>> +	time_t		timestamp;
>>>> +	char		time_buffer[26];
>>>> +	char		*result;
>>>> +
>>>> +	header = (struct commit_header *)buf;
>>>> +	commit_sec = be64_to_cpu(header->h_commit_sec);
>>>> +
>>>> +	timestamp = commit_sec;
>>>> +	result = ctime_r(&timestamp, time_buffer);
>>>> +	if (result)
>>>> +		fprintf(out_file, ", commit at: %s", time_buffer);
>>>
>>> Nit: missing newline in this fprintf... or you could delete the newline
>>> below and change the callsite to:
>>>
>>> 	if (dump_time)
>>> 		dump_commit_time(out_file, buf);
>>> 	fprintf(out_file, "\n");
>>>
>>
>> In my test environment, the string generated by ctime_r comes with a
>> newline character at the end.
> 
> Oh, I guess that /is/ in the manpage:
> 
> 	Broken-down time is stored in the structure tm, described in
> 	tm(3type).
> 
> 	The call ctime(t) is equivalent to asctime(localtime(t)).  It
> 	converts the calendar time t into a null-terminated string of
> 	the form
> 
>             "Wed Jun 30 21:49:08 1993\n"
> 
> and then POSIX has this to say about asctime():
> 
> 	The asctime() function shall convert the broken-down time in the
> 	structure pointed to by timeptr into a string in the form:
> 
> 	Sun Sep 16 01:03:52 1973\n\0
> 
> which is also in ISO C23:
> 
> 	The asctime function converts the broken-down time in the
> 	structure pointed to by timeptr into a string in the form:
> 
> 	Sun Sep 16 01:03:52 1973\n\0
> 
> 	using the equivalent of the following algorithm.

Get it.

> 
> Sigh.
> 
> Reviewed-by: "Darrick J. Wong" <djwong@...nel.org>

Thanks,
  - bin.

>>>
>>> .
>>>
> 
> .
>