UMOUNT_PROPAGATE
if (how & UMOUNT_PROPAGATE)
if (how & UMOUNT_PROPAGATE)
umount_tree(mnt, UMOUNT_PROPAGATE);
umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
umount_tree(m, UMOUNT_PROPAGATE|UMOUNT_SYNC);