On jammy, it works on btrfs:
root@nsn7:/mnt# rm -f foo.img; touch foo.img; fallocate -z -l 10M foo.img; ls -lah foo.img -rw-r--r-- 1 root root 10M abr 19 10:46 foo.img
root@nsn7:/mnt# mount -t btrfs /btrfs.img on /mnt type btrfs (rw,relatime,ssd,space_cache=v2,subvolid=5,subvol=/)
On jammy, it works on btrfs:
root@nsn7:/mnt# rm -f foo.img; touch foo.img; fallocate -z -l 10M foo.img; ls -lah foo.img
-rw-r--r-- 1 root root 10M abr 19 10:46 foo.img
root@nsn7:/mnt# mount -t btrfs ssd,space_ cache=v2, subvolid= 5,subvol= /)
/btrfs.img on /mnt type btrfs (rw,relatime,