One of the hardest parts of working on union mounts is trying to get code reviews. I don’t blame anyone, I’ve lived with this patch set for a year and a half now and I still have a hard time understanding some parts of the code. Also, it’s boring.
A couple of weeks ago, I posted a trivial VFS bugfix and, lo and behold, got some serious bikeshedding action! I thought, “Hey, if I rewrite all of union mounts as 10-line bitop patches I will get more comments!” I failed, but I did get all the core patches down to 140 lines or less (not counting documentation or whitespace changes). It’s like Twitter for kernel patches!
Any kernel developer (and many C developers) should be able to review this patch set. Give it a try, you might be surprised.