[$] Alignment guarantees for kmalloc()

kmalloc() is one of the kernel's fundamental memory-allocationprimitives for relatively small objects. Most of the time, developersdon't worry about the alignment of memory returned fromkmalloc(), and things generally just work. But, Vlastimil Babkasaid during a plenary session at the 2019 Linux Storage,Filesystem, and Memory-Management Summit, every now and thenkmalloc() will do something surprising. He proposed tighteningthe guarantees around object alignment in the hope of generating fewersurprises in the future.