fstrim -Av runs trim on each btrfs subvolume


$ magrathea:~ # fstrim -Av
/.snapshots: 23 GiB (24640622592 bytes) trimmed on /dev/sda3
/var/tmp: 25.7 GiB (27602243584 bytes) trimmed on /dev/sda3
/var/spool: 29.9 GiB (32058798080 bytes) trimmed on /dev/sda3
/var/opt: 29 GiB (31094824960 bytes) trimmed on /dev/sda3
...

$ mount
/dev/sda3 on /.snapshots type btrfs
(rw,relatime,ssd,space_cache,subvolid=258,subvol=/@/.snapshots)
/dev/sda3 on /var/tmp type btrfs
(rw,relatime,ssd,space_cache,subvolid=278,subvol=/@/var/tmp)
/dev/sda3 on /var/spool type btrfs
(rw,relatime,ssd,space_cache,subvolid=277,subvol=/@/var/spool)
/dev/sda3 on /var/opt type btrfs
(rw,relatime,ssd,space_cache,subvolid=276,subvol=/@/var/opt)
...


This is basically bug #1020077 again, but this time with -A instead of -a!