If I was code reviewing this, I would almost certainly insist on a different name to make the WTF go away. I’m not going to suggest one here despite having read the other code comment, as doing so would be bikeshedding — not my codebase and I have no skin in this — the only point I will insist on is that I cannot believe that “three” is a sensible choice of name for whatever it does. Not even what the comment implies it does.

Totally agree, it would definitely be better to rename it, but I read in another comment that the kernel is loathe to rename things. So then it makes you wonder, who allowed 'number_noun = N' in the first place?

"Three is the number of the counting, and the number thou shalt count to is three"

Why my kids ask me questions like this, "who invented the number three," I usually tell them it was someone vaguely European of the Enlightenment era with the same last name. "Ah, it was Ulysses Herman Three, inventor the natural numbers and famed bicyclist." Usually buys me enough time to look it up online.

Or at least require a comment explaining it, before someone needs to dig through the code.

Powers of three, five, and seven sounds a little bit like Totvald's very own little FizzBuzz game hidden in ext4's file-system source code.

> Totvald's very own little FizzBuzz game hidden in ext4's file-system source code

What's that?

Write a filesystem that saves all data blocks to disk, but:

- if the data block id is a multiple of 3, replace its contents with 0x03

- if the data block id is a multiple of 5, replace its contents with 0x05

- if the data block id is a multiple of both 3 and 5, replace its contents with 0x15

> To me, that is a 20 foot tall neon orange flashing Chesterton's fence.

It's not a Chesterton's fence, though. The whole point of Chesterton's fence is that whoever put up the fence that you want to take down couldn't be bothered to add signage explaining why the fence was present, thus either it isn't important to keep the fence up long term, or they're a idiot, in which case there's no reason to belive they were correct in deciding that having a fence there was useful in the first place.

With this fence, if you walk a few meters to the side (read, "select 'ext4_list_backups' and hit ^F and ^G a few times); et viola, there's your signs.

Take down the fence. It's in the filesystem code, what could go wrong?