findmnt(8) and submounts

I just applied (to the util-linux upstream) a patch that allows to list all submounts for defined filesystem(s). For example:

$ findmnt --submounts /sys
TARGET                     SOURCE    FSTYPE  OPTIONS
/sys                       /sys      sysfs   rw,relatime
├─/sys/fs/cgroup           tmpfs     tmpfs   rw,nosuid,nodev,noexec,relat
│ ├─/sys/fs/cgroup/systemd cgroup    cgroup  rw,nosuid,nodev,noexec,relat
│ ├─/sys/fs/cgroup/cpuset  cgroup    cgroup  rw,nosuid,nodev,noexec,relat
│ ├─/sys/fs/cgroup/ns      cgroup    cgroup  rw,nosuid,nodev,noexec,relat
│ ├─/sys/fs/cgroup/cpu     cgroup    cgroup  rw,nosuid,nodev,noexec,relat
│ ├─/sys/fs/cgroup/cpuacct cgroup    cgroup  rw,nosuid,nodev,noexec,relat
│ ├─/sys/fs/cgroup/memory  cgroup    cgroup  rw,nosuid,nodev,noexec,relat
│ ├─/sys/fs/cgroup/devices cgroup    cgroup  rw,nosuid,nodev,noexec,relat
│ ├─/sys/fs/cgroup/freezer cgroup    cgroup  rw,nosuid,nodev,noexec,relat
│ ├─/sys/fs/cgroup/net_cls cgroup    cgroup  rw,nosuid,nodev,noexec,relat
│ └─/sys/fs/cgroup/blkio   cgroup    cgroup  rw,nosuid,nodev,noexec,relat
├─/sys/kernel/security     systemd-1 autofs  rw,relatime,fd=22,pgrp=1,tim
├─/sys/kernel/debug        systemd-1 autofs  rw,relatime,fd=24,pgrp=1,tim
└─/sys/fs/fuse/connections fusectl   fusectl rw,relatime

returns info about /sys and all /sys submounts.

Now you can implement recursive umount in shell, something like:

for d in $(findmnt --list --submounts $MOUNTPOINT -o TARGET -n | tac); do
  umount $d
done

I hope that umount(8) will support something like this ASAP.