add comments about current per_cpu_ptr_to_phys implementation to explain why the logic is more complicated than necessary. Signed-off-by: Dave Young <dyoung at redhat.com> --- mm/percpu.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) --- linux-2.6.orig/mm/percpu.c 2011-11-22 10:18:46.000000000 +0800 +++ linux-2.6/mm/percpu.c 2011-11-23 16:27:01.667562973 +0800 @@ -988,6 +988,19 @@ phys_addr_t per_cpu_ptr_to_phys(void *ad unsigned int cpu; /* + * percpu allocator has special setup for the first chunk, + * which currently supports either embedding in linear address space + * or vmalloc mapping, and, from the second one, the backing + * allocator (currently either vm or km) provides translation. + * + * The addr can be tranlated simply without checking if it falls + * into the first chunk. But the current code reflects better + * how percpu allocator actually works, and the verification can + * discover both bugs in percpu allocator itself and + * per_cpu_ptr_to_phys() callers. So we keep current code. + */ + + /* * The following test on first_start/end isn't strictly * necessary but will speed up lookups of addresses which * aren't in the first chunk.
