[PATCH 08/14] ring-buffer: Make sure the spare sub buffer used for reads has same size
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2023-12-10 04:04:45
Also in:
lkml
Subsystem:
the rest, tracing · Maintainers:
Linus Torvalds, Steven Rostedt, Masami Hiramatsu
From: "Steven Rostedt (Google)" <rostedt@goodmis.org> 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) <rostedt@goodmis.org> --- kernel/trace/trace.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8e9853d38c8d..b3b36d7f1201 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c@@ -7567,6 +7567,7 @@ struct ftrace_buffer_info { struct trace_iterator iter; void *spare; unsigned int spare_cpu; + unsigned int spare_size; unsigned int read; };
@@ -8286,6 +8287,15 @@ tracing_buffers_read(struct file *filp, char __user *ubuf, page_size = ring_buffer_subbuf_size_get(iter->array_buffer->buffer); + /* Make sure the spare matches the current sub buffer size */ + if (info->spare) { + if (page_size != info->spare_size) { + ring_buffer_free_read_page(iter->array_buffer->buffer, + info->spare_cpu, info->spare); + info->spare = NULL; + } + } + if (!info->spare) { info->spare = ring_buffer_alloc_read_page(iter->array_buffer->buffer, iter->cpu_file);
@@ -8294,6 +8304,7 @@ tracing_buffers_read(struct file *filp, char __user *ubuf, info->spare = NULL; } else { info->spare_cpu = iter->cpu_file; + info->spare_size = page_size; } } if (!info->spare)
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2.42.0