linux-kernel - Re: [PATCH] ftrace: add an fsync tracer

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Message-ID: <20081105123604.633105ca@infradead.org>
Date:	Wed, 5 Nov 2008 12:36:04 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Marcin Slusarz <marcin.slusarz@...il.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
	mingo@...e.hu
Subject: Re: [PATCH] ftrace: add an fsync tracer

On Wed, 5 Nov 2008 20:43:31 +0100
Marcin Slusarz <marcin.slusarz@...il.com> wrote:

> On Wed, Nov 05, 2008 at 09:49:02AM -0800, Arjan van de Ven wrote:
> > --- /dev/null
> > +++ b/kernel/trace/trace_fsync.c
> > @@ -0,0 +1,165 @@
> > +/*
> > + * trace fsync calls
> > + * Copyright (C) 2008 Intel Corporation
> > + *
> > + * Based extensively on trace_sched_switch.c
> > + * Copyright (C) 2007 Steven Rostedt <srostedt@...hat.com>
> > + *
> > + */
> > +#include <linux/module.h>
> > +#include <linux/fs.h>
> > +#include <linux/debugfs.h>
> > +#include <linux/kallsyms.h>
> > +#include <linux/uaccess.h>
> > +#include <linux/ftrace.h>
> > +#include <trace/fs.h>
> > +
> > +#include "trace.h"
> > +
> > +static struct trace_array	*ctx_trace;
> > +static int __read_mostly	tracer_enabled;
> > +static atomic_t			fsync_ref;
> > +
> > +static void
> > +probe_do_fsync(struct file *file, int datasync)
> > +{
> > +	char *buffer;
> > +	char *err;
> > +
> > +	if (!atomic_read(&fsync_ref))
> > +		return;
> > +
> > +	if (!tracer_enabled)
> > +		return;
> > +
> > +	buffer = kmalloc(4096, GFP_KERNEL);
> > +	if (!buffer)
> > +		return;
> > +
> > +	memset(buffer, 0, 4096);
> 
> kzalloc?

could do I suppose

> 
> > +	err = d_path(&file->f_path, buffer, 4096);
> > +
> > +	if (IS_ERR(err))
> > +		goto out;
> > +
> > +	ftrace_printk("Process %s is calling fsync on %s\n",
> > +			current->comm, err);
> 
> err? not buffer?

correct, not buffer

it won't work if you use buffer.


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
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