[$] The curious case of O_DIRECTORY|O_CREAT

The open()system call offers a number of flags that modify its behavior; not allcombinations of those flags make sense in a single call. It turns out,though, that the kernel has responded in a surprising way to thecombination of O_CREAT and O_DIRECTORY for a long time.After a 2020 change made that response even more surprising, it seemslikely that this behavior will soon be fixed, resulting in a rare user-visiblesemantic change to a core system call.