doc/cephfs: explain cephfs data and metadata set

Explain how to set application metadata for the CephFS data pool and the
CephFS metadata pool.

Signed-off-by: Zac Dover <zac.dover@proton.me>
(cherry picked from commit 9152f9700420f9735533f276559af87dff97bd75)

diff --git a/doc/cephfs/nfs.rst b/doc/cephfs/nfs.rst
index 6c44b86504226c64752fae97fa44a4e10c9f8a2f..f06911d5cbd0481e7cc5e0b97606b45201cb51f0 100644 (file)
--- a/doc/cephfs/nfs.rst
+++ b/doc/cephfs/nfs.rst
@@ -60,6 +60,18 @@ added as comments 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
 -----------------------------------