_mountinfo: fix mountpoint_for_path()

The correct mount is not the longest one but the last one, because an
earlier longer match could be bind-mounted over. This is also shorter
and simpler.

2 files changed, 7 insertions, 10 deletions

diff --git a/lbup/_mountinfo.py b/lbup/_mountinfo.py
index bbced58..0328131 100644
--- a/lbup/_mountinfo.py
+++ b/lbup/_mountinfo.py
@@ -142,15 +142,10 @@ class MountInfo:
 
     def mountpoint_for_path(self, path):
         """
-        Find the longest mountpoint that is a parent of path.
+        Find the mount entry which contains path.
         """
-        best_match = None
-        for e in self.mounts.values():
-            if (path in e.mount_point and
-                (best_match is None or len(best_match) < len(e.mount_point))):
-                best_match = e.mount_point
+        for mount in reversed(self.mounts.values()):
+            if path in mount.mount_point:
+                return mount
 
-        if best_match is None:
-            raise LookupError('No mountpoint for', path)
-
-        return best_match
+        raise LookupError('No mountpoint for', path)
diff --git a/lbup/targets.py b/lbup/targets.py
index bd53b1e..3f86563 100644
--- a/lbup/targets.py
+++ b/lbup/targets.py
@@ -49,6 +49,8 @@ def _resolve_mntdev(mntinfo, dirs):
     mountpoint = None
     fstype     = None
     for d in dirs:
+        d  = AbsPath(d)
+
         mp = mntinfo.mountpoint_for_path(d)
         e  = list(mntinfo.entries_for_mountpoint(mp))