Commit cd458ba9 authored Jul 18, 2013 by Oleg Nesterov Committed by Steven Rostedt Jul 18, 2013

tracing: Do not (ab)use trace_seq in event_id_read()

event_id_read() has no reason to kmalloc "struct trace_seq"
(more than PAGE_SIZE!), it can use a small buffer instead.

Note: "if (*ppos) return 0" looks strange and even wrong,
simple_read_from_buffer() handles ppos != 0 case corrrectly.

And it seems that almost every user of trace_seq in this file
should be converted too. Unless you use seq_open(), trace_seq
buys nothing compared to the raw buffer, but it needs a bit
more memory and code.

Link: http://lkml.kernel.org/r/20130718184712.GA4786@redhat.com



Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

parent 7710b639

kernel/trace/trace_events.c

+4 −13

Original line number	Diff line number	Diff line
		@@ -947,23 +947,14 @@ static ssize_t
		event_id_read(struct file filp, char __user ubuf, size_t cnt, loff_t *ppos)
		{
		struct ftrace_event_call *call = filp->private_data;
		struct trace_seq *s;
		int r;
		char buf[32];
		int len;

		if (*ppos)
		return 0;

		s = kmalloc(sizeof(*s), GFP_KERNEL);
		if (!s)
		return -ENOMEM;

		trace_seq_init(s);
		trace_seq_printf(s, "%d\n", call->event.type);

		r = simple_read_from_buffer(ubuf, cnt, ppos,
		s->buffer, s->len);
		kfree(s);
		return r;
		len = sprintf(buf, "%d\n", call->event.type);
		return simple_read_from_buffer(ubuf, cnt, ppos, buf, len);
		}

		static ssize_t

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