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        <tr>
          <th>Priority</th>
          <td>medium
          </td>
        </tr>

        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - g_udev_client_query_by_device_number fails on disks with subvolumes"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=66702">66702</a>
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>systemd-bugs@lists.freedesktop.org
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>g_udev_client_query_by_device_number fails on disks with subvolumes
          </td>
        </tr>

        <tr>
          <th>QA Contact</th>
          <td>systemd-bugs@lists.freedesktop.org
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>All
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>jpakkane@gmail.com
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>Other
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>unspecified
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>general
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>systemd
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Created <span class=""><a href="attachment.cgi?id=82191" name="attach_82191" title="Source code to demonstrate the issue">attachment 82191</a> <a href="attachment.cgi?id=82191&action=edit" title="Source code to demonstrate the issue">[details]</a></span>
Source code to demonstrate the issue

Sorry if this bug is filed in the wrong place. Information on GUdev is sparse
and as far as I can tell, systemd is the upstream.

Anyway, the g_udev_client_query_by_device_number function fails on directories
that are in subvolumes. An example is a btrfs file system with two subvolumes,
@ (mounted as root) and @home (mounted as /home). This also happens when using
encrypted home directories.

Having a subvolume might not be the real reason it fails, but that is what
seems to be triggering the issue.

To replicate, download the attached source code. Compile it with "gcc -Wall -o
idnum idnum.c `pkg-config --cflags --libs glib-2.0 gio-2.0 gudev-1.0`".

When run on a plain ext4 volume, the output is this:

./idnum
Device id is 2065.

Whereas on btrfs the output is this:

./idnum
Device id is 25.
Could not get device from num.

Originally filed here:
<a href="https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1197796">https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1197796</a></pre>
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