tests: show mount list on failure for df tests

* init.cfg (dump_mount_list_): A new function to output the
system mount list.
* tests/df/df-symlink.sh: Call dump_mount_list_ upon failure.
* tests/df/over-mount-device.sh: Likewise.
* tests/df/problematic-chars.sh: Likewise.
* tests/df/skip-rootfs.sh: Likewise.
* tests/df/total-verify.sh: Likewise.
* tests/df/unreadable.sh: Likewise.

1 files changed, 8 insertions, 0 deletions

diff --git a/init.cfg b/init.cfg
index 108fd206b..db861944c 100644
--- a/init.cfg
+++ b/init.cfg
@@ -92,6 +92,14 @@ require_mount_list_()
     skip_ "$mount_list_fail"
 }
 
+dump_mount_list_()
+{
+  cat /proc/self/mountinfo ||
+  cat /proc/self/mounts ||
+  cat /proc/mounts ||
+  cat /etc/mtab
+}
+
 require_local_dir_()
 {
   require_mount_list_