Mine

i206m:/data/music# xfs_growfs /data
meta-data=/dev/sda1              isize=256    agcount=32, agsize=19073479 blks
         =                       sectsz=512   attr=0
data     =                       bsize=4096   blocks=610351328, imaxpct=25
         =                       sunit=0      swidth=0 blks, unwritten=1
naming   =version 2              bsize=4096  
log      =internal               bsize=4096   blocks=32768, version=1
         =                       sectsz=512   sunit=0 blks
realtime =none                   extsz=4096   blocks=0, rtextents=0

p34:~# df -h | egrep '(^Filesystem|/dev/md3)'
Filesystem            Size  Used Avail Use% Mounted on
/dev/md3              2.6T  932G  1.7T  36% /raid5
p34:~# xfs_growfs /raid5 
meta-data=/dev/md3               isize=256    agcount=38, agsize=18314368 blks
         =                       sectsz=4096  attr=0
data     =                       bsize=4096   blocks=683740288, imaxpct=25
         =                       sunit=128    swidth=768 blks, unwritten=1
naming   =version 2              bsize=4096
log      =internal               bsize=4096   blocks=32768, version=2
         =                       sectsz=4096  sunit=1 blks
realtime =none                   extsz=3145728 blocks=0, rtextents=0
data blocks changed from 683740288 to 781417472
p34:~# df -h | egrep '(^Filesystem|/dev/md3)'
Filesystem            Size  Used Avail Use% Mounted on 
/dev/md3              3.0T  932G  2.1T  32% /raid5
p34:~#