ceph: allow idmapped permission inode op

Enable ceph_permission() to handle idmapped mounts. This is just a
matter of passing down the mount's idmapping.
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/inode.c

@@ -2970,7 +2970,7 @@ int ceph_permission(struct mnt_idmap *idmap, struct inode *inode,
 	err = ceph_do_getattr(inode, CEPH_CAP_AUTH_SHARED, false);
 
 	if (!err)
-		err = generic_permission(&nop_mnt_idmap, inode, mask);
+		err = generic_permission(idmap, inode, mask);
 	return err;
 }