docs: formatstorage: Update <permissions> docs

- Don't redocument the permissions fields for backingstore, just point to
  the volume docs.
- Clarify that owner/group are inherited from the parent directory at
  volume create/pool build time.
- Clarify that <permissions> fields report runtime values too

docs/formatstorage.html.in

@@ -404,12 +404,18 @@
       <dd>This is currently only useful for directory or filesystem based
         pools, which are mapped as a directory into the local filesystem
         namespace. It provides information about the permissions to use for the
-        final directory when the pool is built. The
-        <code>mode</code> element contains the octal permission set. The
-        <code>owner</code> element contains the numeric user ID. The <code>group</code>
-        element contains the numeric group ID. The <code>label</code> element
-        contains the MAC (eg SELinux) label string.
+        final directory when the pool is built. There are 4 child elements.
+        The <code>mode</code> element contains the octal permission set.
+        The <code>owner</code> element contains the numeric user ID.
+        The <code>group</code> element contains the numeric group ID.
+        If <code>owner</code> or <code>group</code> aren't specified when
+        creating a directory, the values are inherited from the parent
+        directory. The <code>label</code> element contains the MAC (eg SELinux)
+        label string.
         <span class="since">Since 0.4.1</span>
+        For running directory or filesystem based pools, these fields
+        will be filled with the values used by the existing directory.
+        <span class="since">Since 1.2.16</span>
       </dd>
       <dt><code>timestamps</code></dt>
       <dd>Provides timing information about the volume. Up to four
@@ -583,15 +589,20 @@
         volume format type value and the default pool format will be used.
         <span class="since">Since 0.4.1</span></dd>
       <dt><code>permissions</code></dt>
-      <dd>Provides information about the default permissions to use
+      <dd>Provides information about the permissions to use
         when creating volumes. This is currently only useful for directory
         or filesystem based pools, where the volumes allocated are simple
         files. For pools where the volumes are device nodes, the hotplug
-        scripts determine permissions. It contains 4 child elements. The
-        <code>mode</code> element contains the octal permission set. The
-        <code>owner</code> element contains the numeric user ID. The <code>group</code>
-        element contains the numeric group ID. The <code>label</code> element
-        contains the MAC (eg SELinux) label string.
+        scripts determine permissions. There are 4 child elements.
+        The <code>mode</code> element contains the octal permission set.
+        The <code>owner</code> element contains the numeric user ID.
+        The <code>group</code> element contains the numeric group ID.
+        If <code>owner</code> or <code>group</code> aren't specified when
+        creating a supported volume, the values are inherited from the parent
+        directory. The <code>label</code> element contains the MAC (eg SELinux)
+        label string.
+        For existing directory or filesystem based volumes, these fields
+        will be filled with the values used by the existing file.
         <span class="since">Since 0.4.1</span>
       </dd>
       <dt><code>compat</code></dt>
@@ -659,11 +670,8 @@
         <span class="since">Since 0.6.0</span></dd>
       <dt><code>permissions</code></dt>
       <dd>Provides information about the permissions of the backing file.
-        It contains 4 child elements. The
-        <code>mode</code> element contains the octal permission set. The
-        <code>owner</code> element contains the numeric user ID. The <code>group</code>
-        element contains the numeric group ID. The <code>label</code> element
-        contains the MAC (eg SELinux) label string.
+          See volume <code>permissions</code> documentation for explanation
+          of individual fields.
         <span class="since">Since 0.6.0</span>
       </dd>
     </dl>