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.

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_

tests/df/df-symlink.sh

@@ -39,4 +39,6 @@ if test "$(df --output=source | grep -F "$disk" | wc -l)" = 1; then
   compare exp out || fail=1
 fi
 
+test "$fail" = 1 && dump_mount_list_
+
 Exit $fail

tests/df/over-mount-device.sh

@@ -54,4 +54,6 @@ test $(wc -l < out) = 2 || fail=1
 
 compare exp err || fail=1
 
+test "$fail" = 1 && dump_mount_list_
+
 Exit $fail

tests/df/problematic-chars.sh

@@ -41,4 +41,6 @@ test $skip = 1 \
 
 test $(df "$mnt" | wc -l) = 2 || fail=1
 
+test "$fail" = 1 && dump_mount_list_
+
 Exit $fail

tests/df/skip-rootfs.sh

@@ -48,4 +48,6 @@ grep '^rootfs' out || { fail=1; cat out; }
 df -a -x rootfs >out || fail=1
 grep '^rootfs' out && { fail=1; cat out; }
 
+test "$fail" = 1 && dump_mount_list_
+
 Exit $fail

tests/df/total-verify.sh

@@ -62,4 +62,6 @@ cat inode
 $PERL check-df space || fail=1
 $PERL check-df inode || fail=1
 
+test "$fail" = 1 && dump_mount_list_
+
 Exit $fail

tests/df/unreadable.sh

@@ -24,4 +24,6 @@ touch unreadable || fail=1
 chmod a-r unreadable || fail=1
 df unreadable || fail=1
 
+test "$fail" = 1 && dump_mount_list_
+
 Exit $fail