From patchwork Sat Nov 26 20:55:24 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chuck Lever X-Patchwork-Id: 13056580 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 35297C43217 for ; Sat, 26 Nov 2022 20:55:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229436AbiKZUza (ORCPT ); Sat, 26 Nov 2022 15:55:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33074 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229475AbiKZUz3 (ORCPT ); Sat, 26 Nov 2022 15:55:29 -0500 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DBE3B17AA6 for ; Sat, 26 Nov 2022 12:55:28 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 53BEFCE0A4C for ; Sat, 26 Nov 2022 20:55:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 73419C433D6 for ; Sat, 26 Nov 2022 20:55:25 +0000 (UTC) Subject: [PATCH 2/4] SUNRPC: Clean up xdr_write_pages() From: Chuck Lever To: linux-nfs@vger.kernel.org Date: Sat, 26 Nov 2022 15:55:24 -0500 Message-ID: <166949612452.106845.16079864294324208424.stgit@klimt.1015granger.net> In-Reply-To: <166949601705.106845.10614964159272504008.stgit@klimt.1015granger.net> References: <166949601705.106845.10614964159272504008.stgit@klimt.1015granger.net> User-Agent: StGit/1.5.dev3+g9561319 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org 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 Reviewed-by: Jeff Layton --- net/sunrpc/xdr.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c index 336a7c7833e4..f7767bf22406 100644 --- 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; }