On 09.11.21 09:37, Michal Hocko wrote:
I have opposed this patch http://lkml.kernel.org/r/YYj91Mkt4m8ySIWt@dhcp22.suse.cz There was no response to that feedback. I will not go as far as to nack it explicitly because pcp allocator is not an area I would nack patches but seriously, this issue needs a deeper look rather than a paper over patch. I hope we do not want to do a similar thing to all callers of cpu_to_mem.
While we could move it into the !HOLES version of cpu_to_mem(), calling cpu_to_mem() on an offline (and eventually not even present) CPU (with an offline node) is really a corner case.
Instead of additional runtime overhead for all cpu_to_mem(), my take would be to just do it for the random special cases. Sure, we can document that people should be careful when calling cpu_to_mem() on offline CPUs. But IMHO it's really a corner case.