Free space on ZFS is not reported correctly(?)

[namaedayo]

I’m Japanese.
My English ability is not native level, So if I say something wrong,
please don’t be offended.
The clumsy is sorry because it is generated by Google translation.

Free space on ZFS is not reported correctly.
There is a "zpool list -v" in sufficient disk space, but dataset other
than zvol can not use it.

Chassis : HP Prolient ML110 G7
CPU : Xeon E3-1220
Memory : 32GB ECC
HDD : TOSHIBA DT01ACA300 x4
SSD : Intel SSD DC S3500 80GB

ZIL 8GB, L2ARC 16GB (L2ARC has been temporarily manually disabled by D2764)

$ uname -a
FreeBSD namaedayo-hp.local 10.2-RELEASE-p8 FreeBSD 10.2-RELEASE-p8 #14
r292713: Fri Dec 25 11:49:13 JST 2015
root at namaedayo-hp.local:/usr/obj/usr/src/sys/NAMAEDAYO  amd64

$ zpool list -v
NAME         SIZE  ALLOC   FREE  EXPANDSZ   FRAG    CAP  DEDUP  HEALTH  ALTROOT
zpool0      5.44T  4.58T   881G         -    23%    84%  2.08x  ONLINE  -
  mirror    2.72T  2.29T   441G         -    24%    84%
    ada0p2      -      -      -         -      -      -
    ada2p2      -      -      -         -      -      -
  mirror    2.72T  2.29T   441G         -    23%    84%
    ada1p2      -      -      -         -      -      -
    ada3p2      -      -      -         -      -      -
  ada4p2    7.94G  1.51M  7.94G         -    33%     0%

$ zfs list
NAME                                                USED  AVAIL  REFER
 MOUNTPOINT
zpool0                                             5.25T  45.3G   216K  /zpool0
zpool0/FreeBSD-Buckup                               169G  45.3G   169G
 /zpool0/FreeBSD-Buckup
zpool0/FreeBSD-Root                                 862G  45.3G   810G  /
zpool0/Ubuntu-14-04_server                          206G   230G  21.9G  -
zpool0/Ubuntu_Desktop                              82.5G   121G  7.18G  -
zpool0/Ubuntu_Desktop-i386                          135G   115G  48.9G  -
zpool0/freebsd-swap                                66.0G  95.2G  16.1G  -
zpool0/namae-iSCSI                                 82.5G  68.5G  59.3G  -
zpool0/namaedayo_work                               351G  45.3G   346G
 /zpool0/namaedayo_work
zpool0/test-dedup                                  53.8G  45.3G  53.8G
 /zpool0/test-dedup
zpool0/test-lz4                                    47.8G  45.3G  47.8G
 /zpool0/test-lz4
(Omitted because too much)

$ df -h
Filesystem                                           Size    Used
Avail Capacity  Mounted on
zpool0/FreeBSD-Root                                  855G    810G
45G    95%    /
devfs                                                1.0K    1.0K
0B   100%    /dev
linprocfs                                            4.0K    4.0K
0B   100%    /compat/linux/proc
linsysfs                                             4.0K    4.0K
0B   100%    /compat/linux/sys
fdescfs                                              1.0K    1.0K
0B   100%    /dev/fd
procfs                                               4.0K    4.0K
0B   100%    /proc
zpool0/FreeBSD-Buckup                                214G    169G
45G    79%    /zpool0/FreeBSD-Buckup
zpool0/namaedayo_work                                391G    346G
45G    88%    /zpool0/namaedayo_work
zpool0/test-dedup                                     99G     54G
45G    54%    /zpool0/test-dedup
zpool0/test-lz4                                       93G     48G
45G    51%    /zpool0/test-lz4
(Omitted because too much)

$ gpart show
=>        34  5860533101  ada0  GPT  (2.7T)
          34           6        - free -  (3.0K)
          40         128     1  freebsd-boot  (64K)
         168  5860532960     2  freebsd-zfs  (2.7T)
  5860533128           7        - free -  (3.5K)

=>        34  5860533101  ada1  GPT  (2.7T)
          34           6        - free -  (3.0K)
          40         128     1  freebsd-boot  (64K)
         168  5860532960     2  freebsd-zfs  (2.7T)
  5860533128           7        - free -  (3.5K)

=>        34  5860533101  ada2  GPT  (2.7T)
          34           6        - free -  (3.0K)
          40         128     1  freebsd-boot  (64K)
         168  5860532960     2  freebsd-zfs  (2.7T)
  5860533128           7        - free -  (3.5K)

=>        34  5860533101  ada3  GPT  (2.7T)
          34           6        - free -  (3.0K)
          40         128     1  freebsd-boot  (64K)
         168  5860532960     2  freebsd-zfs  (2.7T)
  5860533128           7        - free -  (3.5K)

=>       34  156301421  ada4  GPT  (75G)
         34          6        - free -  (3.0K)
         40       1024     1  freebsd-boot  (512K)
       1064   16777216     2  freebsd-zfs  (8.0G)
   16778280   33554432     3  freebsd-zfs  (16G)
   50332712  105968743        - free -  (51G)

# zdb -C zpool0 | grep 'ashift'
ashift: 12

$ zfs get compressratio zpool0
NAME    PROPERTY       VALUE  SOURCE
zpool0  compressratio  1.13x  -

$ zpool status
  pool: zpool0
 state: ONLINE
  scan: resilvered 1.78T in 3h27m with 0 errors on Tue Jul 15 10:11:44 2014
config:

        NAME        STATE     READ WRITE CKSUM
        zpool0      ONLINE       0     0     0
          mirror-0  ONLINE       0     0     0
            ada0p2  ONLINE       0     0     0
            ada2p2  ONLINE       0     0     0
          mirror-1  ONLINE       0     0     0
            ada1p2  ONLINE       0     0     0
            ada3p2  ONLINE       0     0     0
        logs
          ada4p2    ONLINE       0     0     0

errors: No known data errors