[PATCH v2 2/5] SUNRPC: Add a function for zeroing out a portion of an xdr_stream

[Anna Schumaker <anna@kernel.org>]

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

This will be used during READ_PLUS decoding for handling HOLE segments.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
---
 include/linux/sunrpc/xdr.h |  2 ++
 net/sunrpc/xdr.c           | 23 +++++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/include/linux/sunrpc/xdr.h b/include/linux/sunrpc/xdr.h
index b8f3011e109b..4fd208da1a5e 100644
--- a/include/linux/sunrpc/xdr.h
+++ b/include/linux/sunrpc/xdr.h
@@ -269,6 +269,8 @@ extern bool xdr_stream_subsegment(struct xdr_stream *xdr, struct xdr_buf *subbuf
 				  unsigned int len);
 extern unsigned int xdr_stream_move_subsegment(struct xdr_stream *xdr, unsigned int offset,
 					       unsigned int target, unsigned int length);
+extern unsigned int xdr_stream_zero(struct xdr_stream *xdr, unsigned int offset,
+				    unsigned int length);
 
 /**
  * xdr_set_scratch_buffer - Attach a scratch buffer for decoding data.
diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 9d7c93645f01..5c9ba26875cf 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -1804,6 +1804,29 @@ void xdr_buf_trim_head(struct xdr_buf *buf, unsigned int len)
 }
 EXPORT_SYMBOL_GPL(xdr_buf_trim_head);
 
+/**
+ * xdr_stream_zero - zero out a portion of an xdr_stream
+ * @xdr: an xdr_stream to zero out
+ * @offset: the starting point in the stream
+ * @length: the number of bytes to zero
+ */
+unsigned int xdr_stream_zero(struct xdr_stream *xdr, unsigned int offset,
+			     unsigned int length)
+{
+	struct xdr_buf buf;
+
+	if (xdr_buf_subsegment(xdr->buf, &buf, offset, length) < 0)
+		return 0;
+	if (buf.head[0].iov_len)
+		xdr_buf_iov_zero(buf.head, 0, buf.head[0].iov_len);
+	if (buf.page_len > 0)
+		xdr_buf_pages_zero(&buf, 0, buf.page_len);
+	if (buf.tail[0].iov_len)
+		xdr_buf_iov_zero(buf.tail, 0, buf.tail[0].iov_len);
+	return length;
+}
+EXPORT_SYMBOL_GPL(xdr_stream_zero);
+
 /**
  * xdr_buf_trim - lop at most "len" bytes off the end of "buf"
  * @buf: buf to be trimmed
-- 
2.37.0