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ring-buffer: Make sure the spare sub buffer used for reads has same size

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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.

Link: https://lore.kernel.org/linux-trace-kernel/20231219185629.763664788@goodmis.org

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Google) 2023-12-19 13:54:22 -05:00
parent b81e03a249
commit 4e958db34f
1 changed files with 11 additions and 0 deletions
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11
kernel/trace/trace.c
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@ -7582,6 +7582,7 @@ struct ftrace_buffer_info {
struct trace_iterator iter;
void *spare;
unsigned int spare_cpu;
unsigned int spare_size;
unsigned int read;
};
@ -8301,6 +8302,15 @@ 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);
@ -8309,6 +8319,7 @@ 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)