Me too. Repeatedly, at least once a year, on 3 different machines.

The cause? Filling up the filesystem. Why? Because of OS snapshots.

(Aside: why can they fill it? Because it doesn't give a straight answer to `df -h`. Why not? Because of snapshots.)

That happened recently? A few years ago they added a reserved area used for emergency purposes that should solve situations like that. Can't say I've run into these problems, although I don't tend to run btrfs very heavily because performance becomes unacceptable long before that due to CoW.

https://btrfs.readthedocs.io/en/latest/btrfs-filesystem.html

(Look for "GlobalReserve")

> That happened recently?

It happened to me repeatedly on both openSUSE Leap and openSUSE Tumbleweed during the 4 years I worked for SUSE: 2017-2021.

The `df` command doesn't work: it does not give reliable info. That alone disqualifies this FS for me.

The `fsck` equivalent does not work: every time I have tried, it corrupts volumes into unreadability.

Those 2 things are hard requirements for me.

I raised this internally as significant issues. They were dismissed.