I found out that you can compress the whole of a Btrfs filesystem by defragmenting it with
-czlib, but is it possible to uncompress it again? I'm asking because I managed to stop my system from booting, as
/boot wasn't in a separate partition so
ldlinux.c32 got compressed.
I fixed this by reinstalling syslinux from a chroot after disabling compression from the fstab, but I would like to know if it's possible to uncompress a filesystem completely (and automatically). I'm using Arch Linux by the way.
Before reinstalling syslinux, I also tried defragmenting the filesystem again without specifying the compression options, but this didn't work, so my guess is that defragmenting doesn't disable compression automatically.