[PATCH 3/6] ring-buffer: Initialise reader page order in rb_allocate_cpu_buffer()

[Vincent Donnefort]

In rb_allocate_cpu_buffer(), bpage->order was omitted, leaving it as 0.
This is an issue for a ring-buffer with subbufs bigger than PAGE_SIZE if
when freed: free_buffer_page() relies on this value. Align the value
with the actual allocation size (buffer::subbuf_order).

Fixes: f9b94daa542a ("ring-buffer: Set new size of the ring buffer sub page")
Signed-off-by: Vincent Donnefort <vdonnef...@google.com>

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 9bc467c4dbbb..4747cf427575 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2510,6 +2510,7 @@ rb_allocate_cpu_buffer(struct trace_buffer *buffer, long 
nr_pages, int cpu)
        bpage = alloc_cpu_page(cpu);
        if (!bpage)
                return NULL;
+       bpage->order = cpu_buffer->buffer->subbuf_order;
 
        rb_check_bpage(cpu_buffer, bpage);
 
-- 
2.55.0.654.g21b8a5bc05-goog