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

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Date:	Fri, 19 Jun 2009 16:59:28 +0800
From:	Liming Wang <liming.wang@...driver.com>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org,
	Liming Wang <liming.wang@...driver.com>,
	Li Zefan <lizf@...fujitsu.com>
Subject: [PATCH] ftrace: don't increment @pos in g_start()

how about this one?

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)
-- 
1.6.0.3

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