linux-kernel - [PATCH 07/14] ring-buffer: Do no swap cpu buffers if order is different

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Date:   Sat, 09 Dec 2023 22:54:11 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tzvetomir Stoyanov <tz.stoyanov@...il.com>,
        Vincent Donnefort <vdonnefort@...gle.com>,
        Kent Overstreet <kent.overstreet@...il.com>
Subject: [PATCH 07/14] ring-buffer: Do no swap cpu buffers if order is different

From: "Steven Rostedt (Google)" <rostedt@...dmis.org>

As all the subbuffer order (subbuffer sizes) must be the same throughout
the ring buffer, check the order of the buffers that are doing a CPU
buffer swap in ring_buffer_swap_cpu() to make sure they are the same.

If the are not the same, then fail to do the swap, otherwise the ring
buffer will think the CPU buffer has a specific subbuffer size when it
does not.

Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/ring_buffer.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 4e7eb41695f5..9725aab1b5eb 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -5550,6 +5550,9 @@ int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
 	if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
 		goto out;
 
+	if (buffer_a->subbuf_order != buffer_b->subbuf_order)
+		goto out;
+
 	ret = -EAGAIN;
 
 	if (atomic_read(&buffer_a->record_disabled))
-- 
2.42.0