Torvalds says don't use 5.12 kernel with a swapfile!

[Clarity]

Alert 2021/3/5

[April]

probably best to print a bit of it here as Ubuntu is closely followed by Puppy.

Torvalds goes on to point out that if you aren't using swap at all, this problem wouldn't bite you. And if you're using swap partitions, rather than swap files, you'd be similarly unaffected. Unfortunately, he then reminds us that while he knows an absolute ton about the kernel, he isn't necessarily all that familiar with all the plumbing a normal end user is concerned with:

And, as far as I know, all the normal distributions set things up with swap partitions, not files, because honestly, swapfiles tend to be slower and have various other complexity issues.

Many distributions still default to swap partitions, rather than files. But Ubuntu—which is perhaps the single most widely deployed Linux distribution on the planet—has been installing swapfiles by default for more than four years now. If you're an Ubuntu user (or user of an Ubuntu-derived distro, such as Mint), you've probably got a swapfile, and this bug would probably trash your entire root filesystem.