Merge pull request #26693 from poettering/udev-loop-links

udev: add /dev/loop/by-inode/… + /dev/loop/by-ref/… loopback block device symlinks

test/units/testsuite-50.sh

@@ -430,6 +430,28 @@ mount -t ddi "${image}.gpt" "$T" -o ro,X-mount.mkdir,discard
 umount -R "$T"
 rmdir "$T"
 
+LOOP="$(systemd-dissect --attach --loop-ref=waldo "${image}.raw")"
+
+# Wait until the symlinks we want to test are established
+udevadm trigger -w "$LOOP"
+
+# Check if the /dev/loop/* symlinks really reference the right device
+test /dev/loop/by-ref/waldo -ef "$LOOP"
+
+if [ "$(stat -c '%Hd:%Ld' "${image}.raw")" != '?d:?d' ] ; then
+   # Old stat didn't know the %Hd and %Ld specifiers and turned them into ?d
+   # instead. Let's simply skip the test on such old systems.
+   test "$(stat -c '/dev/loop/by-inode/%Hd:%Ld-%i' "${image}.raw")" -ef "$LOOP"
+fi
+
+# Detach by loopback device
+systemd-dissect --detach "$LOOP"
+
+# Detach by backing inode
+systemd-dissect --attach --loop-ref=waldo "${image}.raw"
+systemd-dissect --detach "${image}.raw"
+(! systemd-dissect --detach "${image}.raw")
+
 echo OK >/testok
 
 exit 0