sunrpc: properly type pc_decode callbacks

Drop the argp argument as it can trivially be derived from the rqstp
argument.  With that all functions now have the same prototype, and we
can remove the unsafe casting to kxdrproc_t.

Signed-off-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/nfsd/nfs3acl.c b/fs/nfsd/nfs3acl.c
index 56cdff4..4e68d6b 100644
--- a/fs/nfsd/nfs3acl.c
+++ b/fs/nfsd/nfs3acl.c
@@ -124,9 +124,10 @@ static __be32 nfsd3_proc_setacl(struct svc_rqst *rqstp)
 /*
  * XDR decode functions
  */
-static int nfs3svc_decode_getaclargs(struct svc_rqst *rqstp, __be32 *p,
-		struct nfsd3_getaclargs *args)
+static int nfs3svc_decode_getaclargs(struct svc_rqst *rqstp, __be32 *p)
 {
+	struct nfsd3_getaclargs *args = rqstp->rq_argp;
+
 	p = nfs3svc_decode_fh(p, &args->fh);
 	if (!p)
 		return 0;
@@ -136,9 +137,9 @@ static int nfs3svc_decode_getaclargs(struct svc_rqst *rqstp, __be32 *p,
 }
 
 
-static int nfs3svc_decode_setaclargs(struct svc_rqst *rqstp, __be32 *p,
-		struct nfsd3_setaclargs *args)
+static int nfs3svc_decode_setaclargs(struct svc_rqst *rqstp, __be32 *p)
 {
+	struct nfsd3_setaclargs *args = rqstp->rq_argp;
 	struct kvec *head = rqstp->rq_arg.head;
 	unsigned int base;
 	int n;
@@ -241,7 +242,7 @@ struct nfsd3_voidargs { int dummy; };
 #define PROC(name, argt, rest, relt, cache, respsize)			\
 {									\
 	.pc_func	= nfsd3_proc_##name,				\
-	.pc_decode	= (kxdrproc_t) nfs3svc_decode_##argt##args,	\
+	.pc_decode	= nfs3svc_decode_##argt##args,			\
 	.pc_encode	= (kxdrproc_t) nfs3svc_encode_##rest##res,	\
 	.pc_release	= nfs3svc_release_##relt,			\
 	.pc_argsize	= sizeof(struct nfsd3_##argt##args),		\