linux-kernel - Re: [PATCH] ftrace: don't increment @pos in g

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Date:	Mon, 22 Jun 2009 08:45:02 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Liming Wang <liming.wang@...driver.com>
CC:	Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ftrace: don't increment @pos in g_start()

Li Zefan wrote:
> Liming Wang wrote:
>> how about this one?
>>
> 
> Yeah, this should work, and cleaner than my version.
> 

Hmmm, the patch is cleaner in diffstat but the resulted code
isn't..

After yours:
   text    data     bss     dec     hex filename
  14879    5480    4240   24599    6017 kernel/trace/ftrace.o

After mine:
   text    data     bss     dec     hex filename
  14873    5480    4240   24593    6011 kernel/trace/ftrace.o


>> It's wrong to increment @pos in g_start(). It causes some entries
>> lost when reading set_graph_function, if the output of the file
>> is large than PAGE_SIZE.
>>
>> [ Impact: fix missing entries when reading set_graph_function ]
>>
>> Signed-off-by: Li Zefan <lizf@...fujitsu.com>
>> Signed-off-by: Liming Wang <liming.wang@...driver.com>
>> ---
>>  kernel/trace/ftrace.c |   14 +++++---------
>>  1 files changed, 5 insertions(+), 9 deletions(-)
>>
>> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
>> index 134e580..1beaac6 100644
>> --- a/kernel/trace/ftrace.c
>> +++ b/kernel/trace/ftrace.c
>> @@ -2495,29 +2495,25 @@ static void *
>>  g_next(struct seq_file *m, void *v, loff_t *pos)
>>  {
>>  	unsigned long *array = m->private;
>> -	int index = *pos;
>>  
>> -	(*pos)++;
>> +	if (v)
>> +		(*pos)++;
>>  
>> -	if (index >= ftrace_graph_count)
>> +	if (*pos >= ftrace_graph_count)
>>  		return NULL;
>>  
>> -	return &array[index];
>> +	return &array[*pos];
>>  }
>>  
>>  static void *g_start(struct seq_file *m, loff_t *pos)
>>  {
>> -	void *p = NULL;
>> -
>>  	mutex_lock(&graph_lock);
>>  
>>  	/* Nothing, tell g_show to print all functions are enabled */
>>  	if (!ftrace_graph_count && !*pos)
>>  		return (void *)1;
>>  
>> -	p = g_next(m, p, pos);
>> -
>> -	return p;
>> +	return g_next(m, NULL, pos);
>>  }
>>  
>>  static void g_stop(struct seq_file *m, void *p)
--
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