[PATCH 2/4] NFSD: Add READ_PLUS data support

[schumaker.anna@gmail.com]

From: Anna Schumaker <Anna.Schumaker@Netapp.com>

This patch adds READ_PLUS support for returning a single
NFS4_CONTENT_DATA segment to the client. This is basically the same as
the READ operation, only with the extra information about data segments.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
---
 fs/nfsd/nfs4proc.c | 17 +++++++++
 fs/nfsd/nfs4xdr.c  | 90 ++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 101 insertions(+), 6 deletions(-)

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 4798667af647..3c11ca9bd5d7 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -2179,6 +2179,16 @@ static inline u32 nfsd4_read_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
 	return (op_encode_hdr_size + 2 + XDR_QUADLEN(rlen)) * sizeof(__be32);
 }
 
+static inline u32 nfsd4_read_plus_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
+{
+	u32 maxcount = svc_max_payload(rqstp);
+	u32 rlen = min(op->u.read.rd_length, maxcount);
+	/* enough extra xdr space for encoding either a hole or data segment. */
+	u32 segments = 1 + 2 + 2;
+
+	return (op_encode_hdr_size + 2 + segments + XDR_QUADLEN(rlen)) * sizeof(__be32);
+}
+
 static inline u32 nfsd4_readdir_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
 {
 	u32 maxcount = 0, rlen = 0;
@@ -2700,6 +2710,13 @@ static const struct nfsd4_operation nfsd4_ops[] = {
 		.op_name = "OP_COPY",
 		.op_rsize_bop = nfsd4_copy_rsize,
 	},
+	[OP_READ_PLUS] = {
+		.op_func = nfsd4_read,
+		.op_release = nfsd4_read_release,
+		.op_name = "OP_READ_PLUS",
+		.op_rsize_bop = nfsd4_read_plus_rsize,
+		.op_get_currentstateid = nfsd4_get_readstateid,
+	},
 	[OP_SEEK] = {
 		.op_func = nfsd4_seek,
 		.op_name = "OP_SEEK",
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 812e82097879..014e05365c17 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -1882,7 +1882,7 @@ static const nfsd4_dec nfsd4_dec_ops[] = {
 	[OP_LAYOUTSTATS]	= (nfsd4_dec)nfsd4_decode_notsupp,
 	[OP_OFFLOAD_CANCEL]	= (nfsd4_dec)nfsd4_decode_offload_status,
 	[OP_OFFLOAD_STATUS]	= (nfsd4_dec)nfsd4_decode_offload_status,
-	[OP_READ_PLUS]		= (nfsd4_dec)nfsd4_decode_notsupp,
+	[OP_READ_PLUS]		= (nfsd4_dec)nfsd4_decode_read,
 	[OP_SEEK]		= (nfsd4_dec)nfsd4_decode_seek,
 	[OP_WRITE_SAME]		= (nfsd4_dec)nfsd4_decode_notsupp,
 	[OP_CLONE]		= (nfsd4_dec)nfsd4_decode_clone,
@@ -3589,10 +3589,11 @@ nfsd4_encode_read(struct nfsd4_compoundres *resp, __be32 nfserr,
 
 	if (nfserr)
 		xdr_truncate_encode(xdr, starting_len);
-
-	read->rd_length = maxcount;
-	*p++ = htonl(eof);
-	*p++ = htonl(maxcount);
+	else {
+		read->rd_length = maxcount;
+		*p++ = htonl(eof);
+		*p++ = htonl(maxcount);
+	}
 
 	return nfserr;
 }
@@ -4264,6 +4265,83 @@ nfsd4_encode_offload_status(struct nfsd4_compoundres *resp, __be32 nfserr,
 		return nfserr_resource;
 	p = xdr_encode_hyper(p, os->count);
 	*p++ = cpu_to_be32(0);
+	return nfserr;
+}
+
+static __be32
+nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp,
+			    struct nfsd4_read *read,
+			    unsigned long maxcount,  u32 *eof)
+{
+	struct xdr_stream *xdr = &resp->xdr;
+	struct file *file = read->rd_nf->nf_file;
+	__be32 nfserr;
+	__be32 *p;
+
+	/* Content type, offset, byte count */
+	p = xdr_reserve_space(xdr, 4 + 8 + 4);
+	if (!p)
+		return nfserr_resource;
+	xdr_commit_encode(xdr);
+
+	if (file->f_op->splice_read &&
+	    test_bit(RQ_SPLICE_OK, &resp->rqstp->rq_flags))
+		nfserr = nfsd4_encode_splice_read(resp, read, file, &maxcount, eof);
+	else
+		nfserr = nfsd4_encode_readv(resp, read, file, &maxcount, eof);
+
+	if (nfserr)
+		return nfserr;
+
+	*p++ = htonl(NFS4_CONTENT_DATA);
+	 p   = xdr_encode_hyper(p, read->rd_offset);
+	*p++ = htonl(maxcount);
+
+	read->rd_offset += maxcount;
+	read->rd_length  = (maxcount > 0) ? read->rd_length - maxcount : 0;
+	return nfserr;
+}
+
+static __be32
+nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr,
+		       struct nfsd4_read *read)
+{
+	unsigned long maxcount;
+	u32 eof;
+	struct xdr_stream *xdr = &resp->xdr;
+	struct file *file;
+	int starting_len = xdr->buf->len;
+	__be32 *p;
+
+	if (nfserr)
+		return nfserr;
+	file = read->rd_nf->nf_file;
+
+	/* eof flag, segment count */
+	p = xdr_reserve_space(xdr, 4 + 4);
+	if (!p) {
+		WARN_ON_ONCE(test_bit(RQ_SPLICE_OK, &resp->rqstp->rq_flags));
+		return nfserr_resource;
+	}
+	if (resp->xdr.buf->page_len &&
+	    test_bit(RQ_SPLICE_OK, &resp->rqstp->rq_flags)) {
+		WARN_ON_ONCE(1);
+		return nfserr_resource;
+	}
+	xdr_commit_encode(xdr);
+
+	maxcount = svc_max_payload(resp->rqstp);
+	maxcount = min_t(unsigned long, maxcount,
+			 (xdr->buf->buflen - xdr->buf->len));
+	maxcount = min_t(unsigned long, maxcount, read->rd_length);
+
+	nfserr = nfsd4_encode_read_plus_data(resp, read, maxcount, &eof);
+	if (nfserr)
+		xdr_truncate_encode(xdr, starting_len);
+	else {
+		*p++ = htonl(eof);
+		*p++ = htonl(1);
+	}
 
 	return nfserr;
 }
@@ -4372,7 +4450,7 @@ static const nfsd4_enc nfsd4_enc_ops[] = {
 	[OP_LAYOUTSTATS]	= (nfsd4_enc)nfsd4_encode_noop,
 	[OP_OFFLOAD_CANCEL]	= (nfsd4_enc)nfsd4_encode_noop,
 	[OP_OFFLOAD_STATUS]	= (nfsd4_enc)nfsd4_encode_offload_status,
-	[OP_READ_PLUS]		= (nfsd4_enc)nfsd4_encode_noop,
+	[OP_READ_PLUS]		= (nfsd4_enc)nfsd4_encode_read_plus,
 	[OP_SEEK]		= (nfsd4_enc)nfsd4_encode_seek,
 	[OP_WRITE_SAME]		= (nfsd4_enc)nfsd4_encode_noop,
 	[OP_CLONE]		= (nfsd4_enc)nfsd4_encode_noop,
-- 
2.24.1