[PATCH v1 06/27] NFSD: Use xdrgen XDR functions for the NFSv2 NULL procedure

[Chuck Lever <cel@kernel.org>]

Hand-written XDR encoders and decoders are difficult to maintain
and can diverge from protocol specifications. Migrating to
xdrgen-generated code improves type safety and ensures the
implementation matches the NFS version 2 protocol specification
exactly.

Convert the NULL procedure to use xdrgen_svc_decode_void and
xdrgen_svc_encode_void, the built-ins declared in
include/linux/sunrpc/xdrgen/_builtins.h. NULL has no arguments or
results, so it is the first procedure converted.

NULL returns no XDR-encoded data, so pc_xdrressize is set to
XDR_void. The argzero field is also set to zero since xdrgen
decoders initialize all decoded values.

Signed-off-by: Chuck Lever <cel@kernel.org>
---
 fs/nfsd/nfsproc.c | 36 +++++++++++++++++++++++++-----------
 1 file changed, 25 insertions(+), 11 deletions(-)

diff --git a/fs/nfsd/nfsproc.c b/fs/nfsd/nfsproc.c
index fd303d7dbad3..0a1c184217e0 100644
--- a/fs/nfsd/nfsproc.c
+++ b/fs/nfsd/nfsproc.c
@@ -57,8 +57,22 @@ static __be32 nfsd_map_io_status(__be32 status)
 	return nfsd_map_status(status);
 }
 
-static __be32
-nfsd_proc_null(struct svc_rqst *rqstp)
+/*
+ * A full specification of each of the following NFSv2 procedures is
+ * available in RFC 1094 Section 2.2.
+ */
+
+/**
+ * nfsd_proc_null - NULL: Do nothing
+ * @rqstp: RPC transaction context
+ *
+ * Return:
+ *   %rpc_success:		RPC executed successfully
+ *
+ * RPC synopsis:
+ *   void NFSPROC_NULL(void) = 0;
+ */
+static __be32 nfsd_proc_null(struct svc_rqst *rqstp)
 {
 	return rpc_success;
 }
@@ -673,15 +687,15 @@ nfsd_proc_statfs(struct svc_rqst *rqstp)
 
 static const struct svc_procedure nfsd_procedures2[18] = {
 	[NFSPROC_NULL] = {
-		.pc_func = nfsd_proc_null,
-		.pc_decode = nfssvc_decode_voidarg,
-		.pc_encode = nfssvc_encode_voidres,
-		.pc_argsize = sizeof(struct nfsd_voidargs),
-		.pc_argzero = sizeof(struct nfsd_voidargs),
-		.pc_ressize = sizeof(struct nfsd_voidres),
-		.pc_cachetype = RC_NOCACHE,
-		.pc_xdrressize = 0,
-		.pc_name = "NULL",
+		.pc_func	= nfsd_proc_null,
+		.pc_decode	= xdrgen_svc_decode_void,
+		.pc_encode	= xdrgen_svc_encode_void,
+		.pc_argsize	= XDR_void,
+		.pc_argzero	= 0,
+		.pc_ressize	= 0,
+		.pc_cachetype	= RC_NOCACHE,
+		.pc_xdrressize	= XDR_void,
+		.pc_name	= "NULL",
 	},
 	[NFSPROC_GETATTR] = {
 		.pc_func = nfsd_proc_getattr,
-- 
2.55.0