ZFS: recursive mounts (via "zfs mount")
It is sometimes beneficial, i.e. during systems recovery, to not mount the whole pool upon import. We can use "zpool import -N" to achieve that, and later use "zfs mount -a" to mount all datasets (with canmount=on).
However, let's say there is a branch of datasets, like a particular rootfs or a user's homedir split into sub-datasets, which we do want to mount.
Currently the needed datasets have to be found with "zfs list -H -o name -r pool/data/set/MYDS" and mounted in succession with a while loop. This is kind of clumsy.
I propose adding a "zfs mount -r pool/data/set/MYDS" which would mount the specified dataset and its children (FS datasets with canmount=on), possibly as a tree rooted under the mountpoint specified with "-o mountpoint=/mnt/a" - or under the default mountpoints, like "zfs mount -a" would do.
Things to think about: what to do with lower-level child datasets which change their mountpoint to be outside this tree - report and ignore them?