doc/cephfs: describe conf opt "client quota df" in quota doc

The ceph config file option (from the client section) "client quota df"
is mentioned in "CephFS Client Capabilities" document but not in the
"CephFS Quota" document. Adding information about this option to this
document too would make it easier for CephFS users to discover,
understand and use this option.

Signed-off-by: Rishabh Dave <ridave@redhat.com>

diff --git a/doc/cephfs/quota.rst b/doc/cephfs/quota.rst
index 6bc26a750d83818fa15335c7e6b6cbd01bd64580..0bc56be12c607aef486563bde00faec2e43babcc 100644 (file)
--- a/doc/cephfs/quota.rst
+++ b/doc/cephfs/quota.rst
@@ -47,6 +47,18 @@ To remove a quota, set the value of extended attribute to ``0``::
   $ getfattr dir1/ -n ceph.quota.max_files
   dir1/: ceph.quota.max_files: No such attribute
 
+Space Usage Reporting and CephFS Quotas
+---------------------------------------
+When the root directory of the CephFS mount has quota set on it, the available
+space on the CephFS reported by space usage report tools (like ``df``) is
+based on quota limit. That is, ``available space = quota limit - used space``
+instead of ``available space = total space - used space``.
+
+This behaviour can be disabled by setting following option in client section
+of ``ceph.conf``::
+
+    client quota df = false
+
 Limitations
 -----------