From patchwork Mon Jun 26 12:09:52 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 9809215 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 99A08603F9 for ; Mon, 26 Jun 2017 12:14:25 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A048D2857B for ; Mon, 26 Jun 2017 12:14:25 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 9470F28582; Mon, 26 Jun 2017 12:14:25 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 33C2528584 for ; Mon, 26 Jun 2017 12:14:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752388AbdFZMOX (ORCPT ); Mon, 26 Jun 2017 08:14:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58810 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752005AbdFZMOS (ORCPT ); Mon, 26 Jun 2017 08:14:18 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 59D504E33D; Mon, 26 Jun 2017 12:14:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 59D504E33D Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=ming.lei@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 59D504E33D Received: from localhost (ovpn-12-86.pek2.redhat.com [10.72.12.86]) by smtp.corp.redhat.com (Postfix) with ESMTP id A588978138; Mon, 26 Jun 2017 12:14:05 +0000 (UTC) From: Ming Lei To: Jens Axboe , Christoph Hellwig , Huang Ying , Andrew Morton , Alexander Viro Cc: linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Ming Lei Subject: [PATCH v2 09/51] block: comment on bio_iov_iter_get_pages() Date: Mon, 26 Jun 2017 20:09:52 +0800 Message-Id: <20170626121034.3051-10-ming.lei@redhat.com> In-Reply-To: <20170626121034.3051-1-ming.lei@redhat.com> References: <20170626121034.3051-1-ming.lei@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Mon, 26 Jun 2017 12:14:12 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP bio_iov_iter_get_pages() used unused bvec spaces for storing page pointer array temporarily, and this patch comments on this usage wrt. multipage bvec support. Signed-off-by: Ming Lei --- block/bio.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/block/bio.c b/block/bio.c index a5db117e8dfa..bf7f25889f6e 100644 --- a/block/bio.c +++ b/block/bio.c @@ -870,6 +870,10 @@ EXPORT_SYMBOL(bio_add_page); * * Pins as many pages from *iter and appends them to @bio's bvec array. The * pages will have to be released using put_page() when done. + * + * The hacking way of using bvec table as page pointer array is safe + * even after multipage bvec is introduced because that space can be + * thought as unused by bio_add_page(). */ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) {