From 67589c71456b0346500629967292dea3802230b6 Mon Sep 17 00:00:00 2001 From: Dave Young Date: Wed, 23 Nov 2011 08:20:53 -0800 Subject: [PATCH] percpu: explain why per_cpu_ptr_to_phys() is more complicated than necessary Add comments about current per_cpu_ptr_to_phys implementation to explain why the logic is more complicated than necessary. -tj: relocated comment into kerneldoc comment Signed-off-by: Dave Young Signed-off-by: Tejun Heo --- mm/percpu.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/mm/percpu.c b/mm/percpu.c index 2473ff06dc76..3bb810a72006 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -978,6 +978,17 @@ bool is_kernel_percpu_address(unsigned long addr) * address. The caller is responsible for ensuring @addr stays valid * until this function finishes. * + * 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. + * * RETURNS: * The physical address for @addr. */ -- 2.20.1