fstests: fixes for config option OVERLAY_MOUNT_OPTIONS

Eryu,

Since v4.13, overlayfs supports mount option index=on/off per mount and kernel config option CONFIG_OVERLAY_FS_INDEX that sets the default system wide value when mount option is not specified.

The behavior of overlayfs may differ for index=on/off, specifically for hardlinks. It is therefore important to be able to test overlayfs with both index=on/off.

To that end exists the OVERLAY_MOUNT_OPTIONS config option, only when I tried to use it I found it was broken in more than one way. This series fixed the use of OVERLAY_MOUNT_OPTIONS and refactors some customized overlay mount helpers along the way.

NOTE for users of kvm-xfstests, this test-appliance change is also required for invoking kvm-xfstests -m index=on/off
https://github.com/tytso/xfstests-bld/pull/4

Amir Goldstein (4):
overlay: remove stale implementation of _scratch_mount_options
overlay: use default overlay mount options _overlay_mount_dirs()
overlay: create helper _overlay_scratch_mount_dirs()
overlay: fix _overlay_config_override of MOUNT_OPTIONS

 common/config     |  4 ++++
 common/rc         | 36 ++++++++++++++++--------------------
 tests/overlay/005 |  2 +-
 tests/overlay/010 |  3 +--
 tests/overlay/014 |  8 +++-----
 tests/overlay/031 | 11 +++++------
 tests/overlay/035 |  3 +--
 tests/overlay/037 | 14 ++++++--------
 tests/overlay/038 |  3 +--
 9 files changed, 38 insertions(+), 46 deletions(-)

2.7.4