From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933483Ab3GRSwP (ORCPT ); Thu, 18 Jul 2013 14:52:15 -0400 Received: from mx1.redhat.com ([209.132.183.28]:64471 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932803Ab3GRSwO (ORCPT ); Thu, 18 Jul 2013 14:52:14 -0400 Date: Thu, 18 Jul 2013 20:47:12 +0200 From: Oleg Nesterov To: Steven Rostedt Cc: Frederic Weisbecker , Masami Hiramatsu , Peter Zijlstra , linux-kernel@vger.kernel.org Subject: [PATCH 2/2] tracing: Do not (ab)use trace_seq in event_id_read() Message-ID: <20130718184712.GA4786@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130718184647.GA4761@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Signed-off-by: Oleg Nesterov --- kernel/trace/trace_events.c | 17 ++++------------- 1 files changed, 4 insertions(+), 13 deletions(-) diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 2c3a8c5..1d2c8db 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -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 -- 1.5.5.1