linux-kernel - [for-next][PATCH 2/2] selftests/ring-buffer: Handle meta-page bigger than the system

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Message-ID: <20240911162758.056529108@goodmis.org>
Date: Wed, 11 Sep 2024 12:27:31 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-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>,
 Shuah Khan <skhan@...uxfoundation.org>,
 linux-kselftest@...r.kernel.org,
 Vincent Donnefort <vdonnefort@...gle.com>
Subject: [for-next][PATCH 2/2] selftests/ring-buffer: Handle meta-page bigger than the system

From: Vincent Donnefort <vdonnefort@...gle.com>

Handle the case where the meta-page content is bigger than the system
page-size. This prepares the ground for extending features covered by
the meta-page.

Cc: Shuah Khan <skhan@...uxfoundation.org>
Cc: linux-kselftest@...r.kernel.org
Link: https://lore.kernel.org/20240910162335.2993310-3-vdonnefort@google.com
Acked-by: Shuah Khan <skhan@...uxfoundation.org>
Signed-off-by: Vincent Donnefort <vdonnefort@...gle.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 tools/testing/selftests/ring-buffer/map_test.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tools/testing/selftests/ring-buffer/map_test.c b/tools/testing/selftests/ring-buffer/map_test.c
index ba12fd31de87..d10a847130fb 100644
--- a/tools/testing/selftests/ring-buffer/map_test.c
+++ b/tools/testing/selftests/ring-buffer/map_test.c
@@ -92,12 +92,22 @@ int tracefs_cpu_map(struct tracefs_cpu_map_desc *desc, int cpu)
 	if (desc->cpu_fd < 0)
 		return -ENODEV;
 
+again:
 	map = mmap(NULL, page_size, PROT_READ, MAP_SHARED, desc->cpu_fd, 0);
 	if (map == MAP_FAILED)
 		return -errno;
 
 	desc->meta = (struct trace_buffer_meta *)map;
 
+	/* the meta-page is bigger than the original mapping */
+	if (page_size < desc->meta->meta_struct_len) {
+		int meta_page_size = desc->meta->meta_page_size;
+
+		munmap(desc->meta, page_size);
+		page_size = meta_page_size;
+		goto again;
+	}
+
 	return 0;
 }
 
-- 
2.45.2