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SUNRPC: Clean up xdr_write_pages()

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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>
This commit is contained in:
Chuck Lever 2022-11-26 15:55:24 -05:00 committed by Chuck Lever
parent da522b5fe1
commit ad3d24c59d
1 changed files with 13 additions and 9 deletions
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22
net/sunrpc/xdr.c
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@ -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;
}