NFS: Add nfs4_update_server

New function nfs4_update_server() moves an nfs_server to a different
nfs_client.  This is done as part of migration recovery.

Though it may be appealing to think of them as the same thing,
migration recovery is not the same as following a referral.

For a referral, the client has not descended into the file system
yet: it has no nfs_server, no super block, no inodes or open state.
It is enough to simply instantiate the nfs_server and super block,
and perform a referral mount.

For a migration, however, we have all of those things already, and
they have to be moved to a different nfs_client.  No local namespace
changes are needed here.

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

3 files changed, 113 insertions, 1 deletions

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index af0325864df6..692fd0e9362f 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -945,7 +945,7 @@ void nfs_server_insert_lists(struct nfs_server *server)
 }
 EXPORT_SYMBOL_GPL(nfs_server_insert_lists);
 
-static void nfs_server_remove_lists(struct nfs_server *server)
+void nfs_server_remove_lists(struct nfs_server *server)
 {
         struct nfs_client *clp = server->nfs_client;
         struct nfs_net *nn;
@@ -962,6 +962,7 @@ static void nfs_server_remove_lists(struct nfs_server *server)
 
         synchronize_rcu();
 }
+EXPORT_SYMBOL_GPL(nfs_server_remove_lists);
 
 /*
  * Allocate and initialise a server record
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index 38da8c2b81ac..e5a6bd12562a 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -154,6 +154,7 @@ struct nfs_client *nfs_get_client(const struct nfs_client_initdata *,
                                   rpc_authflavor_t);
 int nfs_probe_fsinfo(struct nfs_server *server, struct nfs_fh *, struct nfs_fattr *);
 void nfs_server_insert_lists(struct nfs_server *);
+void nfs_server_remove_lists(struct nfs_server *);
 void nfs_init_timeout_values(struct rpc_timeout *, int, unsigned int, unsigned int);
 int nfs_init_server_rpcclient(struct nfs_server *, const struct rpc_timeout *t,
                 rpc_authflavor_t);
@@ -174,6 +175,8 @@ extern struct nfs_server *nfs4_create_server(
                                         struct nfs_subversion *);
 extern struct nfs_server *nfs4_create_referral_server(struct nfs_clone_mount *,
                                                       struct nfs_fh *);
+extern int nfs4_update_server(struct nfs_server *server, const char *hostname,
+                                        struct sockaddr *sap, size_t salen);
 extern void nfs_free_server(struct nfs_server *server);
 extern struct nfs_server *nfs_clone_server(struct nfs_server *,
                                            struct nfs_fh *,
diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
index 511cdce6ecf2..c6eee812337f 100644
--- a/fs/nfs/nfs4client.c
+++ b/fs/nfs/nfs4client.c
@@ -1092,3 +1092,111 @@ error:
         dprintk("<-- nfs4_create_referral_server() = error %d\n", error);
         return ERR_PTR(error);
 }
+
+/*
+ * Grab the destination's particulars, including lease expiry time.
+ *
+ * Returns zero if probe succeeded and retrieved FSID matches the FSID
+ * we have cached.
+ */
+static int nfs_probe_destination(struct nfs_server *server)
+{
+        struct inode *inode = server->super->s_root->d_inode;
+        struct nfs_fattr *fattr;
+        int error;
+
+        fattr = nfs_alloc_fattr();
+        if (fattr == NULL)
+                return -ENOMEM;
+
+        /* Sanity: the probe won't work if the destination server
+         * does not recognize the migrated FH. */
+        error = nfs_probe_fsinfo(server, NFS_FH(inode), fattr);
+
+        nfs_free_fattr(fattr);
+        return error;
+}
+
+/**
+ * nfs4_update_server - Move an nfs_server to a different nfs_client
+ *
+ * @server: represents FSID to be moved
+ * @hostname: new end-point's hostname
+ * @sap: new end-point's socket address
+ * @salen: size of "sap"
+ *
+ * The nfs_server must be quiescent before this function is invoked.
+ * Either its session is drained (NFSv4.1+), or its transport is
+ * plugged and drained (NFSv4.0).
+ *
+ * Returns zero on success, or a negative errno value.
+ */
+int nfs4_update_server(struct nfs_server *server, const char *hostname,
+                       struct sockaddr *sap, size_t salen)
+{
+        struct nfs_client *clp = server->nfs_client;
+        struct rpc_clnt *clnt = server->client;
+        struct xprt_create xargs = {
+                .ident          = clp->cl_proto,
+                .net            = &init_net,
+                .dstaddr        = sap,
+                .addrlen        = salen,
+                .servername     = hostname,
+        };
+        char buf[INET6_ADDRSTRLEN + 1];
+        struct sockaddr_storage address;
+        struct sockaddr *localaddr = (struct sockaddr *)&address;
+        int error;
+
+        dprintk("--> %s: move FSID %llx:%llx to \"%s\")\n", __func__,
+                        (unsigned long long)server->fsid.major,
+                        (unsigned long long)server->fsid.minor,
+                        hostname);
+
+        error = rpc_switch_client_transport(clnt, &xargs, clnt->cl_timeout);
+        if (error != 0) {
+                dprintk("<-- %s(): rpc_switch_client_transport returned %d\n",
+                        __func__, error);
+                goto out;
+        }
+
+        error = rpc_localaddr(clnt, localaddr, sizeof(address));
+        if (error != 0) {
+                dprintk("<-- %s(): rpc_localaddr returned %d\n",
+                        __func__, error);
+                goto out;
+        }
+
+        error = -EAFNOSUPPORT;
+        if (rpc_ntop(localaddr, buf, sizeof(buf)) == 0) {
+                dprintk("<-- %s(): rpc_ntop returned %d\n",
+                        __func__, error);
+                goto out;
+        }
+
+        nfs_server_remove_lists(server);
+        error = nfs4_set_client(server, hostname, sap, salen, buf,
+                                clp->cl_rpcclient->cl_auth->au_flavor,
+                                clp->cl_proto, clnt->cl_timeout,
+                                clp->cl_minorversion, clp->cl_net);
+        nfs_put_client(clp);
+        if (error != 0) {
+                nfs_server_insert_lists(server);
+                dprintk("<-- %s(): nfs4_set_client returned %d\n",
+                        __func__, error);
+                goto out;
+        }
+
+        if (server->nfs_client->cl_hostname == NULL)
+                server->nfs_client->cl_hostname = kstrdup(hostname, GFP_KERNEL);
+        nfs_server_insert_lists(server);
+
+        error = nfs_probe_destination(server);
+        if (error < 0)
+                goto out;
+
+        dprintk("<-- %s() succeeded\n", __func__);
+
+out:
+        return error;
+}