[$] The trouble with MAX_ORDER

One might not think that much could be said about a simple macro defining a
constant integer value.  But the kernel is special, it seems.  A change to
the definition of MAX_ORDER has had a number of follow-on effects,
and the task of cleaning up after this change is not done yet.  So perhaps
a look at MAX_ORDER is in order.

https://lwn.net/Articles/956321/