NFSD: Extract the svcxdr_init_encode() helper

NFSD initializes an encode xdr_stream only after the RPC layer has
already inserted the RPC Reply header. Thus it behaves differently
than xdr_init_encode does, which assumes the passed-in xdr_buf is
entirely devoid of content.

nfs4proc.c has this server-side stream initialization helper, but
it is visible only to the NFSv4 code. Move this helper to a place
that can be accessed by NFSv2 and NFSv3 server XDR functions.

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

1 files changed, 8 insertions, 23 deletions

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index dd9f38d072dd..c57cf09a8b60 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -2262,25 +2262,6 @@ static bool need_wrongsec_check(struct svc_rqst *rqstp)
 	return !(nextd->op_flags & OP_HANDLES_WRONGSEC);
 }
 
-static void svcxdr_init_encode(struct svc_rqst *rqstp,
-			       struct nfsd4_compoundres *resp)
-{
-	struct xdr_stream *xdr = &resp->xdr;
-	struct xdr_buf *buf = &rqstp->rq_res;
-	struct kvec *head = buf->head;
-
-	xdr->buf = buf;
-	xdr->iov = head;
-	xdr->p   = head->iov_base + head->iov_len;
-	xdr->end = head->iov_base + PAGE_SIZE - rqstp->rq_auth_slack;
-	/* Tail and page_len should be zero at this point: */
-	buf->len = buf->head[0].iov_len;
-	xdr_reset_scratch_buffer(xdr);
-	xdr->page_ptr = buf->pages - 1;
-	buf->buflen = PAGE_SIZE * (1 + rqstp->rq_page_end - buf->pages)
-		- rqstp->rq_auth_slack;
-}
-
 #ifdef CONFIG_NFSD_V4_2_INTER_SSC
 static void
 check_if_stalefh_allowed(struct nfsd4_compoundargs *args)
@@ -2335,10 +2316,14 @@ nfsd4_proc_compound(struct svc_rqst *rqstp)
 	struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
 	__be32		status;
 
-	svcxdr_init_encode(rqstp, resp);
-	resp->tagp = resp->xdr.p;
+	resp->xdr = &rqstp->rq_res_stream;
+
+	/* reserve space for: NFS status code */
+	xdr_reserve_space(resp->xdr, XDR_UNIT);
+
+	resp->tagp = resp->xdr->p;
 	/* reserve space for: taglen, tag, and opcnt */
-	xdr_reserve_space(&resp->xdr, 8 + args->taglen);
+	xdr_reserve_space(resp->xdr, XDR_UNIT * 2 + args->taglen);
 	resp->taglen = args->taglen;
 	resp->tag = args->tag;
 	resp->rqstp = rqstp;
@@ -2444,7 +2429,7 @@ nfsd4_proc_compound(struct svc_rqst *rqstp)
 encode_op:
 		if (op->status == nfserr_replay_me) {
 			op->replay = &cstate->replay_owner->so_replay;
-			nfsd4_encode_replay(&resp->xdr, op);
+			nfsd4_encode_replay(resp->xdr, op);
 			status = op->status = op->replay->rp_status;
 		} else {
 			nfsd4_encode_operation(resp, op);