From nobody Sun Dec 28 02:41:47 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8CBA2C4332F for ; Wed, 13 Dec 2023 18:21:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1442386AbjLMSVK (ORCPT ); Wed, 13 Dec 2023 13:21:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44898 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235511AbjLMSUg (ORCPT ); Wed, 13 Dec 2023 13:20:36 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 79E27D5 for ; Wed, 13 Dec 2023 10:20:39 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2797BC43391; Wed, 13 Dec 2023 18:20:39 +0000 (UTC) Received: from rostedt by gandalf with local (Exim 4.97) (envelope-from ) id 1rDTrI-00000002a9n-252N; Wed, 13 Dec 2023 13:21:24 -0500 Message-ID: <20231213182124.270751060@goodmis.org> User-Agent: quilt/0.67 Date: Wed, 13 Dec 2023 13:17:45 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , Tzvetomir Stoyanov , Vincent Donnefort , Kent Overstreet Subject: [PATCH v3 08/15] ring-buffer: Make sure the spare sub buffer used for reads has same size References: <20231213181737.791847466@goodmis.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: "Steven Rostedt (Google)" Now that the ring buffer specifies the size of its sub buffers, they all need to be the same size. When doing a read, a swap is done with a spare page. Make sure they are the same size before doing the swap, otherwise the read will fail. Signed-off-by: Steven Rostedt (Google) --- kernel/trace/trace.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 2e201ef5b1ce..dd7669f6503b 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -7576,6 +7576,7 @@ struct ftrace_buffer_info { struct trace_iterator iter; void *spare; unsigned int spare_cpu; + unsigned int spare_size; unsigned int read; }; =20 @@ -8295,6 +8296,15 @@ tracing_buffers_read(struct file *filp, char __user = *ubuf, =20 page_size =3D ring_buffer_subbuf_size_get(iter->array_buffer->buffer); =20 + /* Make sure the spare matches the current sub buffer size */ + if (info->spare) { + if (page_size !=3D info->spare_size) { + ring_buffer_free_read_page(iter->array_buffer->buffer, + info->spare_cpu, info->spare); + info->spare =3D NULL; + } + } + if (!info->spare) { info->spare =3D ring_buffer_alloc_read_page(iter->array_buffer->buffer, iter->cpu_file); @@ -8303,6 +8313,7 @@ tracing_buffers_read(struct file *filp, char __user *= ubuf, info->spare =3D NULL; } else { info->spare_cpu =3D iter->cpu_file; + info->spare_size =3D page_size; } } if (!info->spare) --=20 2.42.0