According to the archwiki article on a swapfile on btrfs: https://wiki.archlinux.org/title/Btrfs#Swap_file
Tip: Consider creating the subvolume directly below the top-level subvolume, e.g. @swap. Then, make sure the subvolume is mounted to /swap (or any other accessible location).
But… why? I’ve been researching for a bit now, and I still don’t understand the benefit of a subvolume directly below the top level subvolume, as opposed to a nested subvolume.
At first I thought this might be because nested subvolumes are included in snapshots, but that doesn’t seem to be the case, according to a reddit post… but I can’t find anything about this on the arch wiki, gentoo wiki, or the btrfs readthedocs page.
Any ideas? I feel like the tip wouldn’t just be there just because.
Not a specialist, but I suppose it has to do with having different configurations for different top level folder. In Unix-like systems, every top level folder have a different purpose, and what works for the root may not for /tmp, /swap, etc.
In those example, no need to snapshot /tmp, as it is a forder whose file are bound to be deleted, and for which being able to restore has no use.
/swap is pretty similar
, and is often formated with a dedicated filesystem./usr often only change during the package manager transactions, so snapshots are often tied to that, while /home may be set to keep daily snapshots.