This expands a LV used as a virtual disk inside a virtual machine.
First expand the LV on the hypervisor
# lvextend -L500g /dev/vg_guests/lv_myvideo
# lvs|grep myvideo
lv_myvideo vg_guests -wi-ao---- 500.00g
Reboot the hypervisor so all disks are rescanned. There's probably a way of doing this without a reboot but I couldn't figure out how to get that to work;
Check the VM can see the new disk size
# fdisk -l /dev/vdc
Disk /dev/vdc: 500 GiB, 536870912000 bytes, 1048576000 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x60117149
Device Boot Start End Sectors Size Id Type
/dev/vdc1 2048 838860799 838858752 400G 83 Linux
Before continuing, stop any processes using the disk and unmount it.
The partition is still 400G so, using fdisk, delete the primary partition and recreate accepting all defaults, except...
Do not remove the existing disk signature
Do you want to remove the signature? [Y]es/[N]o: N
If you accidentally do remove it, repairing the disk should get it back.
# xfs_repair -L /dev/vdc1
Verify the new size
# fdisk -l /dev/vdc1
Disk /dev/vdc1: 500 GiB, 536869863424 bytes, 1048573952 sectors
Finally remount and grow the file system.
# xfs_growfs /dev/vdc1
