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Commit 67589c71 authored by Dave Young's avatar Dave Young Committed by Tejun Heo
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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: default avatarDave Young <dyoung@redhat.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent a855b84c

mm/percpu.c

+11 −0
Original line number Diff line number Diff line
@@ -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.

 */