Remove unnecessary discard mount option for CephFS

class/defaults.yml

@@ -112,8 +112,7 @@ parameters:
                 # extended here
               mirroring:
                 enabled: false
-            mount_options:
-              discard: true
+            mount_options: {}
             storage_class_config:
               allowVolumeExpansion: true
 

docs/modules/ROOT/pages/references/parameters.adoc

@@ -323,8 +323,7 @@ fspool:
       # extended here
     mirroring:
       enabled: false
-  mount_options:
-    discard: true
+  mount_options: {}
   storage_class_config:
     allowVolumeExpansion: true
 ----
@@ -334,9 +333,11 @@ This configuration creates
 * One `CephFilesystem` resource named `fspool`.
 This CephFS instance is configured to have 3 replicas both for the metadata pool and its single data pool.
 By default, the CephFS instance is configured to assume that metadata will consume roughly 20% and data roughly 80% of the storage cluster.
-* A storage class which creates PVs on the CephFS instance, supports volume expansion and configures PVs to be mounted with `-o discard`.
+* A storage class which creates PVs on the CephFS instance and  supports volume expansion.
 * A `VolumeSnapshotClass` associated with the storage class
 
+NOTE: CephFS doesn't require mount option `discard`, and ceph-csi v3.9.0+ will fail to mount any CephFS volumes if the storage class is configured with mount option `discard`.
+
 The key `data_pools` is provided to avoid having to manage a list of data pools directly in the hierarchy.
 The values of each key in `data_pools` are placed in the resulting CephFS resource's field `.spec.dataPools`
 

tests/golden/cephfs/rook-ceph/rook-ceph/30_storageclasses.yaml

@@ -9,8 +9,7 @@ metadata:
     app.kubernetes.io/name: cephfs-fspool-cluster
     name: cephfs-fspool-cluster
   name: cephfs-fspool-cluster
-mountOptions:
-  - discard
+mountOptions: []
 parameters:
   clusterID: syn-rook-ceph-cluster
   csi.storage.k8s.io/controller-expand-secret-name: rook-csi-cephfs-provisioner