[PATCH v2 3/4] NFSD: Add READ_PLUS hole segment encoding

[schumaker.anna@gmail.com]

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

However, we only encode the hole if it is at the beginning of the range
and treat everything else as data to keep things simple.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
---
 fs/nfsd/nfs4proc.c |  2 +-
 fs/nfsd/nfs4xdr.c  | 47 ++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 9643181591e3..c65939a1e40c 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -2527,7 +2527,7 @@ static inline u32 nfsd4_read_plus_rsize(struct svc_rqst *rqstp, struct nfsd4_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;
+	u32 segments = 2 * (1 + 2 + 2);
 
 	return (op_encode_hdr_size + 2 + segments + XDR_QUADLEN(rlen)) * sizeof(__be32);
 }
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 8efb59d4fda4..1a2f06de651d 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -4417,6 +4417,31 @@ nfsd4_encode_read_plus_data(struct nfsd4_compoundres *resp,
 	return nfserr;
 }
 
+static __be32
+nfsd4_encode_read_plus_hole(struct nfsd4_compoundres *resp, struct nfsd4_read *read,
+			    unsigned long maxcount, u32 *eof)
+{
+	struct file *file = read->rd_nf->nf_file;
+	__be32 *p;
+
+	/* Content type, offset, byte count */
+	p = xdr_reserve_space(&resp->xdr, 4 + 8 + 8);
+	if (!p)
+		return nfserr_resource;
+
+	maxcount = min_t(unsigned long, maxcount, read->rd_length);
+
+	*p++ = cpu_to_be32(NFS4_CONTENT_HOLE);
+	 p   = xdr_encode_hyper(p, read->rd_offset);
+	 p   = xdr_encode_hyper(p, maxcount);
+
+	*eof = (read->rd_offset + maxcount) >= i_size_read(file_inode(file));
+
+	read->rd_offset += maxcount;
+	read->rd_length  = (maxcount > 0) ? read->rd_length - maxcount : 0;
+	return nfs_ok;
+}
+
 static __be32
 nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr,
 		       struct nfsd4_read *read)
@@ -4426,6 +4451,8 @@ nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr,
 	struct xdr_stream *xdr = &resp->xdr;
 	struct file *file;
 	int starting_len = xdr->buf->len;
+	unsigned int segments = 0;
+	loff_t data_pos;
 	__be32 *p;
 
 	if (nfserr)
@@ -4450,12 +4477,28 @@ nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr,
 			 (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);
+	data_pos = vfs_llseek(file, read->rd_offset, SEEK_DATA);
+	if (data_pos == -ENXIO)
+		data_pos = i_size_read(file_inode(file));
+	else if (data_pos < 0)
+		data_pos = read->rd_offset;
+
+	if (data_pos > read->rd_offset) {
+		nfserr = nfsd4_encode_read_plus_hole(resp, read,
+						     data_pos - read->rd_offset, &eof);
+		segments++;
+	}
+
+	if (!nfserr && !eof && read->rd_length > 0) {
+		nfserr = nfsd4_encode_read_plus_data(resp, read, maxcount, &eof);
+		segments++;
+	}
+
 	if (nfserr)
 		xdr_truncate_encode(xdr, starting_len);
 	else {
 		*p++ = htonl(eof);
-		*p++ = htonl(1);
+		*p++ = htonl(segments);
 	}
 
 	return nfserr;
-- 
2.25.0