[PATCH] NFS: use scope from exchange_id to skip reclaim

[Weston Andros Adamson <dros@netapp.com>]

>From Section 8.4.2.1 of the rfc 5661 - We can determine if a RECLAIM_REBOOT
can be skipped if the "eir_server_scope" from the exchange_id proc differs from
previous calls.

Also, in the future server_scope will be useful for determining whether client
trunking is available
---
 fs/nfs/nfs4_fs.h          |    2 ++
 fs/nfs/nfs4proc.c         |   12 ++++++++++++
 fs/nfs/nfs4state.c        |   42 +++++++++++++++++++++++++++++++++++++++++-
 fs/nfs/nfs4xdr.c          |    8 +++++++-
 include/linux/nfs_fs_sb.h |    3 +++
 include/linux/nfs_xdr.h   |    1 +
 6 files changed, 66 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
index c4a6983..bfde1c1 100644
--- a/fs/nfs/nfs4_fs.h
+++ b/fs/nfs/nfs4_fs.h
@@ -48,6 +48,7 @@ enum nfs4_client_state {
 	NFS4CLNT_SESSION_RESET,
 	NFS4CLNT_RECALL_SLOT,
 	NFS4CLNT_LEASE_CONFIRM,
+	NFS4CLNT_SERVER_SCOPE_MISMATCH,
 };
 
 enum nfs4_session_state {
@@ -349,6 +350,7 @@ extern void nfs4_schedule_state_manager(struct nfs_client *);
 extern void nfs4_schedule_stateid_recovery(const struct nfs_server *, struct nfs4_state *);
 extern void nfs41_handle_sequence_flag_errors(struct nfs_client *clp, u32 flags);
 extern void nfs41_handle_recall_slot(struct nfs_client *clp);
+extern void nfs41_handle_server_scope(struct nfs_client *, struct server_scope **);
 extern void nfs4_put_lock_state(struct nfs4_lock_state *lsp);
 extern int nfs4_set_lock_state(struct nfs4_state *state, struct file_lock *fl);
 extern void nfs4_copy_stateid(nfs4_stateid *, struct nfs4_state *, fl_owner_t, pid_t);
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 69c0f3c..2e62974 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -4793,9 +4793,21 @@ int nfs4_proc_exchange_id(struct nfs_client *clp, struct rpc_cred *cred)
 				init_utsname()->domainname,
 				clp->cl_rpcclient->cl_auth->au_flavor);
 
+	res.server_scope = kzalloc(sizeof(struct server_scope), GFP_KERNEL);
+	if (unlikely(!res.server_scope))
+		return -ENOMEM;
+
 	status = rpc_call_sync(clp->cl_rpcclient, &msg, RPC_TASK_TIMEOUT);
+
 	if (!status)
 		status = nfs4_check_cl_exchange_flags(clp->cl_exchange_flags);
+
+	if (!status)
+		nfs41_handle_server_scope(clp, &res.server_scope);
+
+	/* free if not consumed by nfs41_handle_server_scope() */
+	kfree(res.server_scope);
+
 	dprintk("<-- %s status= %d\n", __func__, status);
 	return status;
 }
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 036f5ad..26b0780 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -1619,6 +1619,39 @@ static void nfs4_set_lease_expired(struct nfs_client *clp, int status)
 	set_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state);
 }
 
+static int
+nfs41_cmp_server_scope(struct server_scope *a, struct server_scope *b)
+{
+	int res;
+
+	res = memcmp(a->server_scope, b->server_scope,
+		     min(a->server_scope_sz, b->server_scope_sz));
+
+	if (!res)
+		res = a->server_scope_sz - b->server_scope_sz;
+
+	return res;
+}
+
+void
+nfs41_handle_server_scope(struct nfs_client *clp,
+			  struct server_scope **server_scopep)
+{
+	struct server_scope *server_scope = *server_scopep;
+
+	if (clp->server_scope) {
+		/* if same server_scope, do nothing */
+		if (!nfs41_cmp_server_scope(clp->server_scope, server_scope))
+			return;
+
+		set_bit(NFS4CLNT_SERVER_SCOPE_MISMATCH, &clp->cl_state);
+		kfree(clp->server_scope);
+	}
+
+	clp->server_scope = server_scope;
+	*server_scopep = NULL;
+}
+
 static void nfs4_state_manager(struct nfs_client *clp)
 {
 	int status = 0;
@@ -1639,7 +1672,14 @@ static void nfs4_state_manager(struct nfs_client *clp)
 				goto out_error;
 			}
 			clear_bit(NFS4CLNT_CHECK_LEASE, &clp->cl_state);
-			set_bit(NFS4CLNT_RECLAIM_REBOOT, &clp->cl_state);
+
+			if (test_and_clear_bit(NFS4CLNT_SERVER_SCOPE_MISMATCH,
+					       &clp->cl_state))
+				nfs4_state_start_reclaim_nograce(clp);
+			else
+				set_bit(NFS4CLNT_RECLAIM_REBOOT,
+					&clp->cl_state);
+
 			pnfs_destroy_all_layouts(clp);
 		}
 
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index c3ccd2c..09a19ca 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -4909,11 +4909,17 @@ static int decode_exchange_id(struct xdr_stream *xdr,
 	if (unlikely(status))
 		return status;
 
-	/* Throw away server_scope */
+	/* Save server_scope */
 	status = decode_opaque_inline(xdr, &dummy, &dummy_str);
 	if (unlikely(status))
 		return status;
 
+	if (unlikely(dummy > NFS4_OPAQUE_LIMIT))
+		return -EIO;
+
+	memcpy(res->server_scope->server_scope, dummy_str, dummy);
+	res->server_scope->server_scope_sz = dummy;
+
 	/* Throw away Implementation id array */
 	status = decode_opaque_inline(xdr, &dummy, &dummy_str);
 	if (unlikely(status))
diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index 87694ca..baf72a4 100644
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -16,6 +16,7 @@ struct nfs4_sequence_args;
 struct nfs4_sequence_res;
 struct nfs_server;
 struct nfs4_minor_version_ops;
+struct server_scope;
 
 /*
  * The nfs_client identifies our client state to the server.
@@ -83,6 +84,8 @@ struct nfs_client {
 #ifdef CONFIG_NFS_FSCACHE
 	struct fscache_cookie	*fscache;	/* client index cache cookie */
 #endif
+
+	struct server_scope *server_scope;	/* from exchange_id */
 };
 
 /*
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index 890dce2..31d6df4 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -1039,6 +1039,7 @@ struct server_scope {
 struct nfs41_exchange_id_res {
 	struct nfs_client		*client;
 	u32				flags;
+	struct server_scope		*server_scope;
 };
 
 struct nfs41_create_session_args {
-- 
1.7.4.2