xfs test in xfstests will eat up all the space on i386 testing node with zesty kernel

The xfs test in xfstests test suite will consume all the HDD space on node rizzo with i386 Z-hwe kernel. (It's fine with amd64 Z-hwe kernel on the very same node)

A huge file called "spc" will be generated in ~/autotest/client/tmp/tmp/xfstests-scratch.

This is not a regression as this issue can be reproduced in the proposed kernel and 4.10.0-35-generic.

Error log from jenkins:
http://pastebin.ubuntu.com/25638750/

$ ls -lh
total 254G
-rw------- 1 root root 0 Sep 29 10:11 0
-rw-r--r-- 1 root root 0 Sep 29 09:47 094.fiemap
-rw------- 1 root root 4.8K Sep 29 09:48 096.30645
-rw------- 1 root root 0 Sep 29 10:11 1
-rw------- 1 root root 0 Sep 29 10:11 2
-rw------- 1 root root 0 Sep 29 10:11 3
-rw------- 1 root root 0 Sep 29 10:11 4
-rw------- 1 root root 100M Sep 29 10:11 aligned_vector_rw
-rw-r--r-- 1 root root 23 Sep 29 10:11 append
-rw------- 1 root root 192K Sep 29 10:11 async_direct_io
-rw------- 1 root root 64K Sep 29 09:48 attrval
-rw------- 2 root root 160K Sep 29 09:48 bar
-rw------- 1 root root 8.0K Sep 29 10:11 blackhole
-rw------- 1 root root 24K Sep 29 10:11 buff_direct_coherency
drwxr-xr-x 2 root root 4.0K Sep 29 09:48 dir1
drwxr-xr-x 2 root root 28K Sep 29 09:48 dir1020
drwxr-xr-x 2 root root 4.0K Sep 29 09:48 dir12
drwxr-xr-x 2 root root 4.0K Sep 29 09:48 dir135
drwxr-xr-x 2 root root 36K Sep 29 09:48 dir1530
drwxr-xr-x 2 root root 4.0K Sep 29 09:48 dir18
drwxr-xr-x 2 root root 4.0K Sep 29 09:48 dir2
drwxr-xr-x 2 root root 4.0K Sep 29 09:48 dir202
drwxr-xr-x 2 root root 68K Sep 29 09:48 dir2295
drwxr-xr-x 2 root root 4.0K Sep 29 09:48 dir27
drwxr-xr-x 2 root root 4.0K Sep 29 09:48 dir3
drwxr-xr-x 2 root root 12K Sep 29 09:48 dir303
drwxr-xr-x 2 root root 4.0K Sep 29 09:48 dir4
drwxr-xr-x 2 root root 4.0K Sep 29 09:48 dir40
drwxr-xr-x 2 root root 12K Sep 29 09:48 dir454
drwxr-xr-x 2 root root 4.0K Sep 29 09:48 dir5
drwxr-xr-x 2 root root 4.0K Sep 29 09:48 dir60
drwxr-xr-x 2 root root 20K Sep 29 09:48 dir681
drwxr-xr-x 2 root root 4.0K Sep 29 09:48 dir8
drwxr-xr-x 2 root root 4.0K Sep 29 09:48 dir90
-rw------- 1 root root 6.4M Sep 29 10:11 direct_io
-rw------- 1 root root 128K Sep 29 10:11 eof-zeroing_direct
-rw-r--r-- 1 root root 512K Sep 29 09:47 file1
-rw-r--r-- 1 root root 512K Sep 29 09:47 file2
-rw------- 2 root root 160K Sep 29 09:48 foo
-rw------- 1 root root 128K Sep 29 10:11 fsb_edge_test
drwxr-xr-x 2 root root 4.0K Sep 29 10:11 looptest
-rwsr-xr-x 1 root root 127K Sep 29 10:10 ls
drwx------ 2 root root 4.0K Sep 29 10:10 nosuid
-rw-r--r-- 1 root root 9.4G Sep 29 10:11 small_vector_async
-rw------- 1 root root 254G Sep 29 09:48 spc
---
AlsaDevices:
 total 0
 crw-rw---- 1 root audio 116, 1 Sep 29 04:10 seq
 crw-rw---- 1 root audio 116, 33 Sep 29 04:10 timer
AplayDevices: Error: [Errno 2] No such file or directory
ApportVersion: 2.20.1-0ubuntu2.10
Architecture: i386
ArecordDevices: Error: [Errno 2] No such file or directory
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
CurrentDmesg:

DistroRelease: Ubuntu 16.04
IwConfig: Error: [Errno 2] No such file or directory
Lsusb:
 Bus 002 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
 Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
 Bus 001 Device 003: ID 0424:2514 Standard Microsystems Corp. USB 2.0 Hub
 Bus 001 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
MachineType: Dell Inc. PowerEdge R310
Package: linux (not installed)
PciMultimedia:

ProcEnviron:
 TERM=screen.xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcFB: 0 mgadrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.10.0-35-generic root=UUID=705d1285-e444-46fc-9c99-68bfe6ab3ba9 ro
ProcVersionSignature: User Name 4.10.0-35.39~16.04.1-generic 4.10.17
RelatedPackageVersions:
 linux-restricted-modules-4.10.0-35-generic N/A
 linux-backports-modules-4.10.0-35-generic N/A
 linux-firmware 1.157.12
RfKill: Error: [Errno 2] No such file or directory
Tags: xenial uec-images
Uname: Linux 4.10.0-35-generic i686
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm audio cdrom dialout dip floppy lxd netdev plugdev sudo video
_MarkForUpload: True
dmi.bios.date: 09/06/2013
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.12.0
dmi.board.name: 05XKKK
dmi.board.vendor: Dell Inc.
dmi.board.version: A09
dmi.chassis.type: 23
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvr1.12.0:bd09/06/2013:svnDellInc.:pnPowerEdgeR310:pvr:rvnDellInc.:rn05XKKK:rvrA09:cvnDellInc.:ct23:cvr:
dmi.product.name: PowerEdge R310
dmi.sys.vendor: Dell Inc.