SUNRPC: Clean up xdr_write_pages()

Make it more evident how xdr_write_pages() updates the tail buffer
by using the convention of naming the iov pointer variable "tail".
I spent more than a couple of hours chasing through code to
understand this, so someone is likely to find this useful later.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 336a7c7..f7767bf 100644 (file)
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -1224,30 +1224,34 @@ EXPORT_SYMBOL(xdr_restrict_buflen);
 /**
  * xdr_write_pages - Insert a list of pages into an XDR buffer for sending
  * @xdr: pointer to xdr_stream
- * @pages: list of pages
- * @base: offset of first byte
- * @len: length of data in bytes
+ * @pages: array of pages to insert
+ * @base: starting offset of first data byte in @pages
+ * @len: number of data bytes in @pages to insert
  *
+ * After the @pages are added, the tail iovec is instantiated pointing to
+ * end of the head buffer, and the stream is set up to encode subsequent
+ * items into the tail.
  */
 void xdr_write_pages(struct xdr_stream *xdr, struct page **pages, unsigned int base,
                 unsigned int len)
 {
        struct xdr_buf *buf = xdr->buf;
-       struct kvec *iov = buf->tail;
+       struct kvec *tail = buf->tail;
+
        buf->pages = pages;
        buf->page_base = base;
        buf->page_len = len;
 
-       iov->iov_base = (char *)xdr->p;
-       iov->iov_len  = 0;
-       xdr->iov = iov;
+       tail->iov_base = xdr->p;
+       tail->iov_len = 0;
+       xdr->iov = tail;
 
        if (len & 3) {
                unsigned int pad = 4 - (len & 3);
 
                BUG_ON(xdr->p >= xdr->end);
-               iov->iov_base = (char *)xdr->p + (len & 3);
-               iov->iov_len  += pad;
+               tail->iov_base = (char *)xdr->p + (len & 3);
+               tail->iov_len += pad;
                len += pad;
                *xdr->p++ = 0;
        }