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Date: Wed, 20 Jan 2010 19:56:16 +0100
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>, linux-kernel@vger.kernel.org,
       Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 4/6] tracing: Change trace_seq to use separate buffer
Message-ID: <20100120185614.GB6194@nowhere>
References: <4B556078.7000004@cn.fujitsu.com>
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On Tue, Jan 19, 2010 at 03:34:16PM +0800, Lai Jiangshan wrote:
> @@ -526,19 +526,19 @@ event_format_read(struct file *filp, char __user *ubuf, size_t cnt,
>  {
>  	struct ftrace_event_call *call = filp->private_data;
>  	struct ftrace_event_field *field;
> -	struct trace_seq *s;
> +	struct trace_seq seq, *s = &seq;
> +	unsigned char *buffer;
>  	int common_field_count = 5;
> -	char *buf;
>  	int r = 0;
>  
>  	if (*ppos)
>  		return 0;
>  
> -	s = kmalloc(sizeof(*s), GFP_KERNEL);
> -	if (!s)
> +	buffer = (unsigned char *)__get_free_page(GFP_KERNEL);
> +	if (!buffer)
>  		return -ENOMEM;
>  
> -	trace_seq_init(s);
> +	trace_seq_init(s, buffer, PAGE_SIZE);



May be can we use a paired trace_seq_init_page/trace_seq_free_page,
to sum up a bit the above pattern.