From the log you will see it stuck after generic/165 for the btrfs filesystem:
08:40:48 DEBUG| [stdout] generic/163 16s
08:41:01 DEBUG| [stdout] generic/164 12s
08:41:15 DEBUG| [stdout] generic/165 14s
And it will be killed by the time-out setting.
This issue can be spotted across different kernel, and it looks like a test case issue.
Possible fix could be found in upstream repo:
https://git.kernel.org/pub/scm/fs/xfs/xfstests-dev.git/commit/tests/generic/166?id=132f37916d2c5f64b857ecaf2072ce7891c5f5ba
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-image-4.13.0-17-lowlatency 4.13.0-17.20~16.04.1
ProcVersionSignature: User Name 4.13.0-17.20~16.04.1-lowlatency 4.13.8
Uname: Linux 4.13.0-17-lowlatency x86_64
ApportVersion: 2.20.1-0ubuntu2.10
Architecture: amd64
Date: Fri Nov 10 10:11:21 2017
ProcEnviron:
TERM=xterm-256color
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=en_US.UTF-8
SHELL=/bin/bash
SourcePackage: linux-hwe-edge
UpgradeStatus: No upgrade log present (probably fresh install)
very old bug, with no action on it, marking bug as incomplete and will
close in 5 days if no update.