声明：xfs文件系统不支持lv缩容，这里是ext4文件系统

首先看下现在的文件系统挂载和使用情况

[root@aiker01 ~]# df -hT               
Filesystem          Type      Size  Used Avail Use% Mounted on
/dev/mapper/cl-root xfs       8.6G  5.3G  3.4G  62% /
devtmpfs            devtmpfs  2.4G     0  2.4G   0% /dev
tmpfs               tmpfs     2.4G     0  2.4G   0% /dev/shm
tmpfs               tmpfs     2.4G  8.7M  2.4G   1% /run
tmpfs               tmpfs     2.4G     0  2.4G   0% /sys/fs/cgroup
/dev/mapper/cl-home xfs       4.0G   33M  4.0G   1% /home
/dev/mapper/cl-var  xfs       3.0G  159M  2.8G   6% /var
/dev/sda2           xfs       497M  132M  366M  27% /boot
/dev/mapper/vg1-lv1 ext4      5.9G   16M  5.6G   1% /mnt
tmpfs               tmpfs     479M     0  479M   0% /run/user/0
/dev/mapper/vg2-lv2 ext4      3.9G   16M  3.7G   1% /data
[root@aiker01 ~]# ll /mnt/
total 36
-rw-r--r-- 1 root root     9 Dec  7 02:26 1.txt
-rw-r--r-- 1 root root     9 Dec  7 02:26 2.txt
drwxr-xr-x 2 root root  4096 Dec  7 02:34 6
drwxr-xr-x 2 root root  4096 Dec  7 02:34 7
drwxr-xr-x 2 root root  4096 Dec  7 02:34 8
drwx------ 2 root root 16384 Dec  6 03:02 lost+found
[root@aiker01 ~]# cat /mnt/1.txt 
12345678

卸载掉lv1卷

[root@aiker01 ~]# umount /mnt/

设置lv卷大小
下面的做法经过试验是会报错的：

[root@aiker01 ~]# lvresize -L 2G /dev/vg1/lv1 
  WARNING: Reducing active logical volume to 2.00 GiB.
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce vg1/lv1? [y/n]: 
  WARNING: Invalid input ''.
Do you really want to reduce vg1/lv1? [y/n]: y
  Size of logical volume vg1/lv1 changed from <5.99 GiB (1533 extents) to 2.00 GiB (512 extents).
  Logical volume vg1/lv1 successfully resized.
[root@aiker01 ~]# e2fsck -f !$
e2fsck -f /dev/vg1/lv1
e2fsck 1.42.9 (28-Dec-2013)
The filesystem size (according to the superblock) is 1569792 blocks
The physical size of the device is 524288 blocks
Either the superblock or the partition table is likely to be corrupt!
Abort? y
[root@aiker01 ~]# e2fsck -f /dev/vg1/lv1
e2fsck 1.42.9 (28-Dec-2013)
The filesystem size (according to the superblock) is 1569792 blocks
The physical size of the device is 524288 blocks
Either the superblock or the partition table is likely to be corrupt!
Abort? yes

正确的做法
刚才的错误可以修正回之前的大小：

[root@aiker01 ~]# lvresize -l 1533 /dev/vg1/lv1  
  Size of logical volume vg1/lv1 changed from <2.00 GiB (511 extents) to <5.99 GiB (1533 extents).
  Logical volume vg1/lv1 successfully resized.
[root@aiker01 ~]# resize2fs /dev/vg1/lv1 5.99G
resize2fs 1.42.9 (28-Dec-2013)
resize2fs: Invalid new size: 5.99G

[root@aiker01 ~]# e2fsck -f /dev/vg1/lv1         
e2fsck 1.42.9 (28-Dec-2013)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/vg1/lv1: 16/392448 files (0.0% non-contiguous), 45115/1569792 blocks
[root@aiker01 ~]# resize2fs /dev/vg1/lv1 4G 
resize2fs 1.42.9 (28-Dec-2013)
Resizing the filesystem on /dev/vg1/lv1 to 1048576 (4k) blocks.
The filesystem on /dev/vg1/lv1 is now 1048576 blocks long.

[root@aiker01 ~]# lvresize -L 4G /dev/vg1/lv1  #设置lv大小为4G
  WARNING: Reducing active logical volume to 4.00 GiB.
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce vg1/lv1? [y/n]: y
  Size of logical volume vg1/lv1 changed from <5.99 GiB (1533 extents) to 4.00 GiB (1024 extents).
  Logical volume vg1/lv1 successfully resized.

[root@aiker01 ~]# !e2  #检查是lv有错误
e2fsck -f /dev/vg1/lv1 
e2fsck 1.42.9 (28-Dec-2013)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/vg1/lv1: 16/261632 files (0.0% non-contiguous), 36907/1048576 blocks
[root@aiker01 ~]# lvdisplay  /dev/vg1/lv1

--- Logical volume ---
  LV Path                /dev/vg1/lv1
  LV Name                lv1
  VG Name                vg1
  LV UUID                q6dAzJ-1dbC-2EoY-Fzcp-QqEE-enuU-FS5BLT
  LV Write Access        read/write
  LV Creation host, time aiker01, 2017-12-06 03:02:40 +0800
  LV Status              available
  # open                 0
  LV Size                4.00 GiB
  Current LE             1024
  Segments               3
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:4

    [root@aiker01 ~]# vgdisplay  /dev/vg1
    --- Volume group ---
  VG Name               vg1
  System ID             
  Format                lvm2
  Metadata Areas        3
  Metadata Sequence No  23
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               0
  Max PV                0
  Cur PV                3
  Act PV                3
  VG Size               <5.99 GiB
  PE Size               4.00 MiB
  Total PE              1533
  Alloc PE / Size       1024 / 4.00 GiB
  Free  PE / Size       509 / <1.99 GiB
  VG UUID               dx3XD9-rQBV-QtBu-EebN-wgjI-CQcn-36iIbm

     [root@aiker01 ~]# mount /dev/vg1/lv1 /mnt/
[root@aiker01 ~]# ll /mnt/
total 36
-rw-r--r-- 1 root root     9 Dec  7 02:26 1.txt
-rw-r--r-- 1 root root     9 Dec  7 02:26 2.txt
drwxr-xr-x 2 root root  4096 Dec  7 02:34 6
drwxr-xr-x 2 root root  4096 Dec  7 02:34 7
drwxr-xr-x 2 root root  4096 Dec  7 02:34 8
drwx------ 2 root root 16384 Dec  6 03:02 lost+found
[root@aiker01 ~]# cat /mnt/1.txt 
12345678
[root@aiker01 ~]# df -hT
Filesystem          Type      Size  Used Avail Use% Mounted on
/dev/mapper/cl-root xfs       8.6G  5.3G  3.4G  62% /
devtmpfs            devtmpfs  2.4G     0  2.4G   0% /dev
tmpfs               tmpfs     2.4G     0  2.4G   0% /dev/shm
tmpfs               tmpfs     2.4G  8.7M  2.4G   1% /run
tmpfs               tmpfs     2.4G     0  2.4G   0% /sys/fs/cgroup
/dev/mapper/cl-home xfs       4.0G   33M  4.0G   1% /home
/dev/mapper/cl-var  xfs       3.0G  159M  2.8G   6% /var
/dev/sda2           xfs       497M  132M  366M  27% /boot
tmpfs               tmpfs     479M     0  479M   0% /run/user/0
/dev/mapper/vg2-lv2 ext4      3.9G   16M  3.7G   1% /data
/dev/mapper/vg1-lv1 ext4      3.9G   16M  3.7G   1% /mnt

可以清楚的查看后lv1缩容后的大小，里面的文件并没有损坏。