Merge pull request ceph#51204 from zdover23/wip-doc-2023-04-25-cephfs…

…-nfs-ganesha-permissions

doc/cephfs: explain cephfs data and metadata set

Reviewed-by: Anthony D'Atri <anthony.datri@gmail.com>

doc/cephfs/nfs.rst

@@ -56,6 +56,18 @@ in the sample conf. There are options to do the following:
 - enable read delegations (need at least v13.0.1 ``libcephfs2`` package
   and v2.6.0 stable ``nfs-ganesha`` and ``nfs-ganesha-ceph`` packages)
 
+.. important::
+
+   Under certain conditions, NFS access using the CephFS FSAL fails. This
+   causes an error to be thrown that reads "Input/output error". Under these
+   circumstances, the application metadata must be set for the CephFS metadata
+   and CephFS data pools. Do this by running the following command:
+
+   .. prompt:: bash $
+
+      ceph osd pool application set <cephfs_metadata_pool> cephfs <cephfs_data_pool> cephfs
+
+
 Configuration for libcephfs clients
 -----------------------------------