On Mon 07-12-15 14:13:46, Johannes Weiner wrote: > On Mon, Dec 07, 2015 at 06:10:00PM +0000, Dave Gordon wrote: > > Exporting random uncontrolled variables from the kernel to loaded modules is > > not really considered best practice. It would be preferable to provide an > > accessor function - which is just what the declaration says we have; the > > implementation as a static inline (and/or macro) is what causes the problem > > here. > > No, what causes the problem is thinking we can't trust in-kernel code. This is not about the trust. It is about a clear API and separation. > If somebody screws up, we can fix it easily enough. Sure, we shouldn't > be laying traps and create easy-to-misuse interfaces, but that's not > what's happening here. There is no reason to add function overhead to > what should be a single 'mov' instruction. The mere fact that the current implementation is a simple atomic_long_read is a detail and not important for the API. The function is not used in any hot path where a single function call overhead would be a performance killer. Exporting implementation details to random users tends to add maintenance burden in future. I think it is natural to export symbols which are consumed by modules and that will be get_nr_swap_pages(). I do not even understand the resistance against that. Anyway I am not going to argue about it more. I have raised my review comment and leave the decision to Chris/Andrew. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>