re-sizing a lv on a ext4 root partition with 1.5G available in vg

lvextend_resize2fs.txt

vgs output:
  VG        #PV #LV #SN Attr   VSize VFree
  vg_centos   1   2   0 wz--n- 9.51g 1.50g
=============
lvdisplay /dev/vg_centos/lv_root output:
  --- Logical volume ---
  LV Path                /dev/vg_centos/lv_root
  LV Name                lv_root
  VG Name                vg_centos
  LV UUID                yADUTB-na3L-7kLC-vylN-GGYB-b14w-viBIjb
  LV Write Access        read/write
  LV Creation host, time centos, 2015-08-23 02:37:26 +0000
  LV Status              available
  # open                 1
  LV Size                7.51 GiB
  Current LE             1922
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:0
   
=============
df -h output:
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_centos-lv_root
                      7.3G  625M  6.3G   9% /
tmpfs                 939M     0  939M   0% /dev/shm
/dev/vda1             477M   30M  422M   7% /boot
=============
command as root:
lvmextend -L+1G /dev/vg_centos/lv_root
=============
command as root:
resize2fs /dev/vg_centos/lv_root
=============
vgs output:
  VG        #PV #LV #SN Attr   VSize VFree  
  vg_centos   1   2   0 wz--n- 9.51g 512.00m
=============
df -h output:
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_centos-lv_root
                      8.3G  655M  7.2G   9% /
tmpfs                 939M     0  939M   0% /dev/shm
/dev/vda1             477M   30M  422M   7% /boot