Intermittant failures to create msdos extended partitions on disks with 4k sectors due to a bug in libparted

[Wesley Wiedenmeier]

When attempting to format a disk with a dos partition table using an extended partition there are occasional crashes that appear to be caused by a bug in parted. This only happens when disks are using 4k sectors. It seems to happen whether using scsi-hd or virtio-blk in qemu.

This only happens maybe 1/5 times, and only seems to happen when many tests are being run concurrently, suggesting that it has something to do with disk read/write times. However, I have not been able to narrow down the cause yet. While this is a bug in parted, and curtin is calling parted correctly here, I'm filing a bug against curtin as well because I know ideally curtin will no longer use parted at some point in the future. I will file a bug in parted upstream once I have created a test case that causes this failure reliably without using curtin.

This failure was originally found in lp:~wesley-wiedenmeier/curtin/clear-holders-storagetests/ but in order to reproduce it without using storagetests, I have added vmtests that isolate dos logical partitioning and run both with 512 and 4K sector sizes in the branch
lp:~wesley-wiedenmeier/curtin/dos_extended_partition_vmtest/

The error message:

[ 22.622692] cloud-init[2389]: previous partition number for 'disk1extended' found to be '2'
[ 22.632965] cloud-init[2389]: previous partition: /sys/class/block/vdb/vdb2
[ 22.637165] cloud-init[2389]: previous partition.size_sectors: 524288.0
[ 22.654718] cloud-init[2389]: previous partition.start_sectors: 786688.0
[ 22.670006] cloud-init[2389]: adding partition 'disk1extended' to disk 'disk1' (ptable: 'msdos')
[ 22.684773] cloud-init[2389]: partnum: 3 offset_sectors: 1310976.0 length_sectors: 1049343
[ 22.712750] cloud-init[2389]: Running command ['parted', '/dev/vdb', '--script', 'mkpart', 'extended', '1310976 .0s', '2360319.0s'] with allowed return codes [0] (shell=False, capture=True)
[ 23.040850] cloud-init[2389]: An error occured handling 'disk1extended': ProcessExecutionError Unexpected err or while running command.
[ 23.066064] cloud-init[2389]: Command: ['parted', '/dev/vdb', '--script', 'mkpart', 'extended', '1310976.0s', ' 2360319.0s']
[ 23.072602] cloud-init[2389]: Exit code: -11
[ 23.074978] cloud-init[2389]: Reason: -
[ 23.080224] cloud-init[2389]: Stdout: ''
[ 23.128547] cloud-init[2389]: Stderr: "\n\nYou found a bug in GNU Parted! Here's what you have to do:\n\nDon't panic! The bug has most likely not affected any of your data.\nHelp us to fix this bug by doing the following:\n\n Check whether the bug has already been fixed by checking\nthe last version of GNU Parted that you can find at:\n\n \thttp://ftp.gnu.org/gnu/parted/\n\nPlease check this version prior to bug reporting.\n\nIf this has not been fixe d yet or if you don't know how to check,\nplease visit the GNU Parted website:\n\n\thttp://www.gnu.org/software/pa rted\n\nfor further information.\n\nYour report should contain the version of this release (3.2)\nalong with the e rror message below, the output of\n\n\tparted DEVICE unit co print unit s print\n\nand the following history of co mmands you entered.\nAlso include any additional information about your setup you\nconsider important.\n"
[ 23.145099] cloud-init[2389]: finish: cmd-install/stage-partitioning/builtin/cmd-block-meta: FAIL: failed: conf iguring partition: disk1extended