2988 nfssrv: need ability to go to submounts for v3 and v2 protocols
Portions contributed by: Marcel Telka <marcel.telka@nexenta.com>
Portions contributed by: Jean McCormack <jean.mccormack@nexenta.com>
Reviewed by: Yuri Pankov <yuri.pankov@nexenta.com>
Reviewed by: Alek Pinchuk <alek.pinchuk@nexenta.com>
Reviewed by: Dan Fields <dan.fields@nexenta.com>
Reviewed by: Dan McDonald <danmcd@joyent.com>
Change-Id: I6fdf110cc17e789353c4442b83a46cb80643456e

@@ -98,10 +98,27 @@
                          default values associated with the global tag in
                          /etc/nfs/nfslog.conf are used.  Support of NFS server
                          logging is only available for NFS Version 2 and
                          Version 3 requests.
 
+               nohide    By default, if server exports two filesystems, one of
+                         which is mounted as a child of the other, NFS Version
+                         2 and Version 3 clients must mount both filesystems
+                         explicitly in order to access them.  If a client only
+                         mounts the parent, it will see an empty directory at
+                         the location where the other filesystem is mounted.
+
+                         Setting the nohide option on a filesystem causes it
+                         to no longer be hidden in this manner, and the client
+                         will be able to move from the parent filesystem to
+                         this one without noticing the change.  However, some
+                         NFS clients or applications may not function
+                         correctly when this option is used.  In particular,
+                         files on different underlying filesystems may appear
+                         to have the same inode numbers.  The nohide option
+                         only applies to NFS Version 2 and Version 3 requests.
+
                noaclfab  By default, the NFS server will fabricate POSIX-draft
                          style ACLs in response to ACL requests from NFS
                          Version 2 or Version 3 clients accessing shared file
                          systems that do not support POSIX-draft ACLs (such as
                          ZFS).  Specifying noaclfab disables this behavior.

@@ -468,6 +485,12 @@
      The NFS Version 4 protocol does not use the mountd processing and the
      client's use of /export/foo does not work as it does with NFS Version 2
      and Version 3 and the client receives an error when attempting to mount
      /export/foo.
 
+     The nohide option violates RFC 1094, Network File System Protocol
+     Specification and RFC 1813, NFS: Network File System Version 3 Protocol
+     Specification
+
+     The nohide option is provided for compatibility with Linux NFS.
+
 illumos                         March 23, 2017                         illumos