+ dd if=/dev/zero of=foo bs=1M count=1 seek=2000
1+0 records in
1+0 records out
1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.00151753 s, 691 MB/s
+ sudo kpartx -s -v -a foo
+ sudo parted foo -s -- mklabel msdos
+ sudo parted foo -s -- mkpart primary ext4 2M 2G
+ sudo kpartx -s -v -a /dev/loop0
add map loop0p1 (252:0): 0 4093952 linear 7:0 4096
+ sudo mkfs -t ext4 /dev/mapper/loop0p1
mke2fs 1.43.1 (08-Jun-2016)
Discarding device blocks:   4096/511744             done                            
Creating filesystem with 511744 4k blocks and 128000 inodes
Filesystem UUID: d370161d-e07a-4bc2-85e4-7ef80a29b547
Superblock backups stored on blocks: 
	32768, 98304, 163840, 229376, 294912

Allocating group tables:  0/16     done                            
Writing inode tables:  0/16     done                            
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information:  0/16     done

+ sudo sfdisk -l foo
Disk foo: 2 GiB, 2098200576 bytes, 4098048 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: 0x05fa1637

Device Boot Start     End Sectors Size Id Type
foo1         4096 4098047 4093952   2G 83 Linux
+ sudo kpartx -s -v -d foo
del devmap : loop0p1
loop deleted : /dev/loop0
+ qemu-img resize -f raw foo 8G
Image resized.
+ sudo kpartx -s -v -a foo
add map loop0p1 (252:0): 0 4093952 linear 7:0 4096
+ sudo kpartx -s -v -d /dev/loop0
del devmap : loop0p1
+ sudo growpart /dev/loop0 1
attempt to resize /dev/loop0 failed. sfdisk output below:
| Backup files:
|          MBR (offset     0, size   512): /tmp/growpart.4UjUFH/orig.save-loop0-0x00000000.bak
| 
| Disk /dev/loop0: 8 GiB, 8589934592 bytes, 16777216 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: 0x05fa1637
| 
| Old situation:
| 
| Device       Boot Start     End Sectors Size Id Type
| /dev/loop0p1       4096 4098047 4093952   2G 83 Linux
| 
| >>> Script header accepted.
| >>> Script header accepted.
| >>> Script header accepted.
| >>> Script header accepted.
| >>> Created a new DOS disklabel with disk identifier 0x05fa1637.
| Created a new partition 1 of type 'Linux' and of size 8 GiB.
| /dev/loop0p2: 
| New situation:
| 
| Device       Boot Start      End  Sectors Size Id Type
| /dev/loop0p1       4096 16777182 16773087   8G 83 Linux
| 
| The partition table has been altered.
| Calling ioctl() to re-read partition table.
| Re-reading the partition table failed.: Invalid argument
| The kernel still uses the old table. The new table will be used at the next reboot or after you run partprobe(8) or kpartx(8).
FAILED: failed to resize
***** WARNING: Resize failed, attempting to revert ******
512+0 records in
512+0 records out
512 bytes copied, 0.0120644 s, 42.4 kB/s
***** Appears to have gone OK ****
+ echo 2
2
+ sudo kpartx -s -v -a /dev/loop0
add map loop0p1 (252:0): 0 4093952 linear 7:0 4096
+ sudo e2fsck -f -y -E discard /dev/mapper/loop0p1
e2fsck 1.43.1 (08-Jun-2016)
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/mapper/loop0p1: 11/128000 files (0.0% non-contiguous), 17736/511744 blocks
+ sudo resize2fs /dev/mapper/loop0p1
resize2fs 1.43.1 (08-Jun-2016)
The filesystem is already 511744 (4k) blocks long.  Nothing to do!

+ sudo zerofree /dev/mapper/loop0p1
+ sudo kpartx -s -v -d foo
device-mapper: remove ioctl on loop0p1 failed: Device or resource busy
loop deleted : /dev/loop0
+ rm foo