ring-buffer: Add cast to unsigned long addr passed to virt_to_page()

The sub-buffer pages are held in an unsigned long array, and when it is
passed to virt_to_page() a cast is needed.

Link: https://lore.kernel.org/all/[email protected]/
Link: https://lore.kernel.org/linux-trace-kernel/[email protected]

Cc: Masami Hiramatsu <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Fixes: 117c392 ("ring-buffer: Introducing ring-buffer mapping functions")
Reported-by: Stephen Rothwell <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: rostedt

kernel/trace/ring_buffer.c

@@ -6283,7 +6283,7 @@ static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer,
 	}
 
 	while (p < nr_pages) {
-		struct page *page = virt_to_page(cpu_buffer->subbuf_ids[s]);
+		struct page *page = virt_to_page((void *)cpu_buffer->subbuf_ids[s]);
 		int off = 0;
 
 		if (WARN_ON_ONCE(s >= nr_subbufs)) {