From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4513CC49EBE for ; Sat, 26 Jun 2021 13:05:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 37A8E61C6A for ; Sat, 26 Jun 2021 13:05:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230241AbhFZNIL (ORCPT ); Sat, 26 Jun 2021 09:08:11 -0400 Received: from mail.kernel.org ([198.145.29.99]:33908 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230044AbhFZNH6 (ORCPT ); Sat, 26 Jun 2021 09:07:58 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id AAD8261C3F; Sat, 26 Jun 2021 13:05:36 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.94.2) (envelope-from ) id 1lx807-000Eh3-O3; Sat, 26 Jun 2021 09:05:35 -0400 Message-ID: <20210626130535.582288691@goodmis.org> User-Agent: quilt/0.66 Date: Sat, 26 Jun 2021 09:04:10 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Linus Torvalds Subject: [for-next][PATCH 06/24] tracing: Simplify the max length test when using the filtering temp buffer References: <20210626130404.033700863@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Steven Rostedt (VMware)" When filtering trace events, a temp buffer is used because the extra copy from the temp buffer into the ring buffer is still faster than the direct write into the ring buffer followed by a discard if the filter does not match. But the data that can be stored in the temp buffer is a PAGE_SIZE minus the ring buffer event header. The calculation of that header size is complex, but using the helper macro "struct_size()" can simplify it. Link: https://lore.kernel.org/stable/CAHk-=whKbJkuVmzb0hD3N6q7veprUrSpiBHRxVY=AffWZPtxmg@mail.gmail.com/ Suggested-by: Linus Torvalds Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 2e592885a167..a0a84ff46ecd 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2735,8 +2735,10 @@ trace_event_buffer_lock_reserve(struct trace_buffer **current_rb, (trace_file->flags & (EVENT_FILE_FL_SOFT_DISABLED | EVENT_FILE_FL_FILTERED)) && (entry = this_cpu_read(trace_buffered_event))) { /* Try to use the per cpu buffer first */ + int max_len = PAGE_SIZE - struct_size(entry, array, 1); + val = this_cpu_inc_return(trace_buffered_event_cnt); - if ((len < (PAGE_SIZE - sizeof(*entry) - sizeof(entry->array[0]))) && val == 1) { + if (val == 1 && likely(len <= max_len)) { trace_event_setup(entry, type, trace_ctx); entry->array[0] = len; return entry; -- 2.30.2