nullmounting zfs fs with children

[Nezmer]

Hi, 

Is this normal behaviour?

# zfs create -p -o mountpoint=/zfstest/subdir0/subdir1/subdir2 POOL/zfstest/subdir0/subdir1/subdir2
# echo 2 > /zfstest/subdir0/subdir1/subdir2/file2
# echo 1 > /zfstest/subdir0/subdir1/file1

# find /zfstest
/zfstest
/zfstest/subdir0
/zfstest/subdir0/subdir1
/zfstest/subdir0/subdir1/file1
/zfstest/subdir0/subdir1/subdir2
/zfstest/subdir0/subdir1/subdir2/file2

# mkdir /nulltest
# mount_nullfs /zfstest /nulltest

# find /nulltest
/nulltest
/nulltest/subdir0
/nulltest/subdir0/subdir1
/nulltest/subdir0/subdir1/file1
/nulltest/subdir0/subdir1/subdir2

# echo 0 > /zfstest/subdir0/file0

# find /zfstest
/zfstest
/zfstest/subdir0
/zfstest/subdir0/subdir1
/zfstest/subdir0/subdir1/file1
/zfstest/subdir0/subdir1/subdir2
/zfstest/subdir0/subdir1/subdir2/file2
/zfstest/subdir0/file0

# find /nulltest
/nulltest
/nulltest/subdir0
/nulltest/subdir0/subdir1
/nulltest/subdir0/subdir1/file1
/nulltest/subdir0/subdir1/subdir2
/nulltest/subdir0/file0

# umount /nulltest
# zfs destroy -r POOL/zfstest

# find /zfstest
/zfstest
/zfstest/subdir0
/zfstest/subdir0/subdir1
/zfstest/subdir0/subdir1/file1
/zfstest/subdir0/subdir1/subdir2
/zfstest/subdir0/file0

# find /nulltest
/nulltest
/nulltest/subdir0
/nulltest/subdir0/subdir1
/nulltest/subdir0/subdir1/file1
/nulltest/subdir0/subdir1/subdir2
/nulltest/subdir0/file0

I noticed this behaviour when I wanted to nullmount my "/usr/home" inside a chroot:

# mount|grep /usr/home
POOL/usr/home on /usr/home (zfs, local, noatime)
POOL/usr/home/nezmer on /usr/home/nezmer (zfs, local, noatime)
POOL/usr/home/nezmer/Mail on /usr/home/nezmer/Mail (zfs, local, noatime)
POOL/usr/home/nezmer/pkgs on /usr/home/nezmer/pkgs (zfs, local, noatime)
POOL/usr/home/nezmer/srcs on /usr/home/nezmer/srcs (zfs, local, noatime)
/usr/home on /chroot/usr/home (nullfs, local)

# find /usr/home -maxdepth 4|wc
    7267    7289  390127

# find /chroot/usr/home
/chroot/usr/home
/chroot/usr/home/nezmer