NFS: Add sysfs links to sunrpc clients for nfs_clients

For the general and state management nfs_client under each mount, create
symlinks to their respective rpc_client sysfs entries.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

NFS: add superblock sysfs entries

Create a sysfs directory for each mount that corresponds to the mount's
nfs_server struct. As the mount is being constructed, use the name
"server-n", but rename it to the "MAJOR:MINOR" of the mount after assigning
a device_id. The rename approach allows us to populate the mount's directory
with links to the various rpc_client objects during the mount's
construction. The naming convention (MAJOR:MINOR) can be used to reference
a particular NFS mount's sysfs tree.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

NFS: Make all of /sys/fs/nfs network-namespace unique

Expand the NFS network-namespaced sysfs from /sys/fs/nfs/net down one level
into /sys/fs/nfs by moving the "net" kobject onto struct
nfs_netns_client and setting it up during network namespace init.

This prepares the way for superblock kobjects within /sys/fs/nfs that will
only be visible to matching network namespaces.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

NFS: rename nfs_client_kobj to nfs_net_kobj

Match the variable names to the sysfs structure.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

NFSv4: Fix up RCU annotations for struct nfs_netns_client

The identifier is read as an RCU protected string. Its value may
be changed during the lifetime of the network namespace by writing
a new string into the sysfs pseudofile (at which point, we free the
old string only after a call to synchronize_rcu()).

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

NFS: Use the correct style for SPDX License Identifier

This patch corrects the SPDX License Identifier style in
header file related to NFS Client support.
For C header files Documentation/process/license-rules.rst
mandates C-like comments (opposed to C source files where
C++ style should be used).

Changes made by using a script provided by Joe Perches here:
https://lkml.org/lkml/2019/2/7/46.

Suggested-by: Joe Perches <joe@perches.com>
Signed-off-by: Nishad Kamdar <nishadkamdar@gmail.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

NFS: Add sysfs support for per-container identifier

In order to identify containers to the NFS client, we add a per-net
sysfs attribute that udev can fill with the appropriate identifier.
The identifier could be a unique hostname, but in most cases it
will probably be a persisted uuid.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

NFS: Create a root NFS directory in /sys/fs/nfs

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>