tests: avoid false failure with BTRFS subvolumes

* tests/df/df-symlink.sh: Only check the symmetry of
the source <-> target lookup, when the source is only mounted once,
which isn't the case if '.' is a BTRFS subvolume for example.
Reported by Assaf Gordon on a default OpenSUSE 42.1 install.

diff --git a/tests/df/df-symlink.sh b/tests/df/df-symlink.sh
index ed4c7882c3f4af89a4dcc91329f33887287d27e9..a9d8c962391c5e34f7a89dfe070487593daab07d 100755 (executable)
--- a/tests/df/df-symlink.sh
+++ b/tests/df/df-symlink.sh
@@ -32,7 +32,11 @@ compare exp out || fail=1
 # This was not the case in coreutil-8.22 on systems
 # where the device in the mount list was a symlink itself.
 # I.e., '.' => /dev/mapper/fedora-home -> /dev/dm-2
-df --out=source,target '.' > out || fail=1
-compare exp out || fail=1
+# Restrict this test to systems with a 1:1 mapping between
+# source and target.  This excludes for example BTRFS sub-volumes.
+if test "$(df --output=source | grep -F "$disk" | wc -l)" = 1; then
+  df --out=source,target '.' > out || fail=1
+  compare exp out || fail=1
+fi
 
 Exit $fail