NFS: Add nfs4_unique_id boot parameter

An optional boot parameter is introduced to allow client
administrators to specify a string that the Linux NFS client can
insert into its nfs_client_id4 id string, to make it both more
globally unique, and to ensure that it doesn't change even if the
client's nodename changes.

If this boot parameter is not specified, the client's nodename is
used, as before.

Client installation procedures can create a unique string (typically,
a UUID) which remains unchanged during the lifetime of that client
instance.  This works just like creating a UUID for the label of the
system's root and boot volumes.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

3 files changed, 13 insertions, 1 deletions

diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
index 832503c7a00e..a525fdefccde 100644
--- a/fs/nfs/nfs4_fs.h
+++ b/fs/nfs/nfs4_fs.h
@@ -380,6 +380,9 @@ extern bool nfs4_disable_idmapping;
 extern unsigned short max_session_slots;
 extern unsigned short send_implementation_id;
 
+#define NFS4_CLIENT_ID_UNIQ_LEN         (64)
+extern char nfs4_client_id_uniquifier[NFS4_CLIENT_ID_UNIQ_LEN];
+
 /* nfs4sysctl.c */
 #ifdef CONFIG_SYSCTL
 int nfs4_register_sysctl(void);
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index b5834abfcbff..9aa97112426f 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -4068,9 +4068,13 @@ static unsigned int
 nfs4_init_uniform_client_string(const struct nfs_client *clp,
                                 char *buf, size_t len)
 {
+        char *nodename = clp->cl_rpcclient->cl_nodename;
+
+        if (nfs4_client_id_uniquifier[0] != '\0')
+                nodename = nfs4_client_id_uniquifier;
         return scnprintf(buf, len, "Linux NFSv%u.%u %s",
                                 clp->rpc_ops->version, clp->cl_minorversion,
-                                clp->cl_rpcclient->cl_nodename);
+                                nodename);
 }
 
 /**
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 056138d45c11..56f02a9bd6d3 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -2662,6 +2662,7 @@ unsigned int nfs_idmap_cache_timeout = 600;
 bool nfs4_disable_idmapping = true;
 unsigned short max_session_slots = NFS4_DEF_SLOT_TABLE_SIZE;
 unsigned short send_implementation_id = 1;
+char nfs4_client_id_uniquifier[NFS4_CLIENT_ID_UNIQ_LEN] = "";
 
 EXPORT_SYMBOL_GPL(nfs_callback_set_tcpport);
 EXPORT_SYMBOL_GPL(nfs_callback_tcpport);
@@ -2669,6 +2670,7 @@ EXPORT_SYMBOL_GPL(nfs_idmap_cache_timeout);
 EXPORT_SYMBOL_GPL(nfs4_disable_idmapping);
 EXPORT_SYMBOL_GPL(max_session_slots);
 EXPORT_SYMBOL_GPL(send_implementation_id);
+EXPORT_SYMBOL_GPL(nfs4_client_id_uniquifier);
 
 #define NFS_CALLBACK_MAXPORTNR (65535U)
 
@@ -2694,6 +2696,8 @@ static struct kernel_param_ops param_ops_portnr = {
 module_param_named(callback_tcpport, nfs_callback_set_tcpport, portnr, 0644);
 module_param(nfs_idmap_cache_timeout, int, 0644);
 module_param(nfs4_disable_idmapping, bool, 0644);
+module_param_string(nfs4_unique_id, nfs4_client_id_uniquifier,
+                        NFS4_CLIENT_ID_UNIQ_LEN, 0600);
 MODULE_PARM_DESC(nfs4_disable_idmapping,
                 "Turn off NFSv4 idmapping when using 'sec=sys'");
 module_param(max_session_slots, ushort, 0644);
@@ -2702,6 +2706,7 @@ MODULE_PARM_DESC(max_session_slots, "Maximum number of outstanding NFSv4.1 "
 module_param(send_implementation_id, ushort, 0644);
 MODULE_PARM_DESC(send_implementation_id,
                 "Send implementation ID with NFSv4.1 exchange_id");
+MODULE_PARM_DESC(nfs4_unique_id, "nfs_client_id4 uniquifier string");
 MODULE_ALIAS("nfs4");
 
 #endif /* CONFIG_NFS_V4 */