Make --one-file-system work for bind mounts

2 files changed, 20 insertions, 1 deletions

diff --git a/NEWS b/NEWS
index bec96a03..31154454 100644
--- a/NEWS
+++ b/NEWS
@@ -39,6 +39,11 @@ Minor changes:
 * Lars Wirzenius added a chapter on participating in the Obnam project
   to the manual.
 
+* Lars Wirzenius changed `--one-file-system` to work for bind mounts.
+  It only works for bind mounts that exist at the time when Obnam
+  starts, however. Also, `/proc/mounts` must be an accurate list of
+  mount points.
+
 Bug fixes:
 
 * The manual and manual page used to claim you could break only the
diff --git a/obnamlib/plugins/one_file_system_plugin.py b/obnamlib/plugins/one_file_system_plugin.py
index 94101b8d..7b584c88 100644
--- a/obnamlib/plugins/one_file_system_plugin.py
+++ b/obnamlib/plugins/one_file_system_plugin.py
@@ -34,14 +34,28 @@ class OneFileSystemPlugin(obnamlib.ObnamPlugin):
 
     def config_loaded(self):
         if self.app.settings['one-file-system']:
+            self.load_mount_points()
             self.app.hooks.add_callback('backup-exclude', self.exclude)
 
+    def load_mount_points(self):
+        try:
+            with open('/proc/mounts', 'r') as f:
+                self.mount_points = self.parse_proc_mounts(f)
+        except EnvironmentError:
+            pass
+
+    def parse_proc_mounts(self, f):
+        return [
+            line.split()[1]
+            for line in f
+        ]
+
     def exclude(self, **kwargs):
         st = kwargs['stat_result']
         root_metadata = kwargs['root_metadata']
         pathname = kwargs['pathname']
         exclude = kwargs['exclude']
 
-        if st.st_dev != root_metadata.st_dev:
+        if st.st_dev != root_metadata.st_dev or pathname in self.mount_points:
             logging.debug('Excluding (one-file-system): %s', pathname)
             exclude[0] = True