SUNRPC: Split out _shift_data_right_tail()

xdr_shrink_pagelen() is very similar to what we need for hole expansion,
so split out the common code into its own function that can be used by
both functions.
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/xdr.c

@@ -266,6 +266,46 @@ _shift_data_right_pages(struct page **pages, size_t pgto_base,
 	} while ((len -= copy) != 0);
 }
 
+static unsigned int
+_shift_data_right_tail(struct xdr_buf *buf, unsigned int pgfrom, size_t len)
+{
+	struct kvec *tail = buf->tail;
+	unsigned int tailbuf_len;
+	unsigned int result = 0;
+	size_t copy;
+
+	tailbuf_len = buf->buflen - buf->head->iov_len - buf->page_len;
+
+	/* Shift the tail first */
+	if (tailbuf_len != 0) {
+		unsigned int free_space = tailbuf_len - tail->iov_len;
+
+		if (len < free_space)
+			free_space = len;
+		if (len > free_space)
+			len = free_space;
+
+		tail->iov_len += free_space;
+		copy = len;
+
+		if (tail->iov_len > len) {
+			char *p = (char *)tail->iov_base + len;
+			memmove(p, tail->iov_base, tail->iov_len - free_space);
+			result += tail->iov_len - free_space;
+		} else
+			copy = tail->iov_len;
+
+		/* Copy from the inlined pages into the tail */
+		_copy_from_pages((char *)tail->iov_base,
+					 buf->pages,
+					 buf->page_base + pgfrom,
+					 copy);
+		result += copy;
+	}
+
+	return result;
+}
+
 /**
  * _copy_to_pages
  * @pages: array of pages
@@ -446,39 +486,13 @@ xdr_shrink_bufhead(struct xdr_buf *buf, size_t len)
 static unsigned int
 xdr_shrink_pagelen(struct xdr_buf *buf, size_t len)
 {
-	struct kvec *tail;
-	size_t copy;
 	unsigned int pglen = buf->page_len;
-	unsigned int tailbuf_len;
 	unsigned int result;
 
-	result = 0;
-	tail = buf->tail;
 	if (len > buf->page_len)
 		len = buf-> page_len;
-	tailbuf_len = buf->buflen - buf->head->iov_len - buf->page_len;
 
-	/* Shift the tail first */
-	if (tailbuf_len != 0) {
-		unsigned int free_space = tailbuf_len - tail->iov_len;
-
-		if (len < free_space)
-			free_space = len;
-		tail->iov_len += free_space;
-
-		copy = len;
-		if (tail->iov_len > len) {
-			char *p = (char *)tail->iov_base + len;
-			memmove(p, tail->iov_base, tail->iov_len - len);
-			result += tail->iov_len - len;
-		} else
-			copy = tail->iov_len;
-		/* Copy from the inlined pages into the tail */
-		_copy_from_pages((char *)tail->iov_base,
-				buf->pages, buf->page_base + pglen - len,
-				copy);
-		result += copy;
-	}
+	result = _shift_data_right_tail(buf, pglen - len, len);
 	buf->page_len -= len;
 	buf->buflen -= len;
 	/* Have we truncated the message? */