linux-kernel - Re: [PATCH] tracing: dont reset set_ftrace_filter/notrace when opened with r/w perm

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Date:	Mon, 20 Jul 2009 08:55:54 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Jiri Olsa <jolsa@...hat.com>
CC:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracing: dont reset set_ftrace_filter/notrace when	opened
 with r/w perm

Jiri Olsa wrote:
> On Fri, Jul 17, 2009 at 05:37:24PM +0800, Li Zefan wrote:
>> Jiri Olsa wrote:
>>> If user setup set_ftrace_filter/set_ftrace_notrace files and then opens them
>>> with read&write permissions, the previous setup will be removed.
>>>
>> Currently:
>>
>>  # echo 'sys_open sys_close' > set_ftrace_filter
>>  # cat set_ftrace_filter
>>  sys_open
>>  sys_close
>>
>> After your patch:
>>
>>  # echo 'sys_open sys_close' > set_ftrace_filter
>>  # cat set_ftrace_filter
>>  sys_close
>>
> 
> oops, sry I missed this..
> 
> Following patch adds new FTRACE_ITER_RESET flag, as the decision needs
> to be taken in "open" and applied in "write".  I'm not sure whats the
> policy for adding new flags, but it looks ok to me.
> 

I have no strong opinion whether to do the reset in "open" or in first
"write".

All said, I think this is cleaner, without introducing a new flag:

@@ -2260,6 +2256,9 @@ ftrace_regex_write(struct file *file, const char __user *ubuf,
 		return 0;
 
 	mutex_lock(&ftrace_regex_lock);
+	if (file->f_pos == 0 &&
+	    (file->f_mode & FMODE_WRITE) && !(file->f_flags & O_APPEND))
+		ftrace_filter_reset(enable);
 
 	if (file->f_mode & FMODE_READ) {
 		struct seq_file *m = file->private_data;
--
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