From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C4994C433FF for ; Sun, 4 Aug 2019 23:54:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A7D182089F for ; Sun, 4 Aug 2019 23:54:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726709AbfHDXyJ (ORCPT ); Sun, 4 Aug 2019 19:54:09 -0400 Received: from mail105.syd.optusnet.com.au ([211.29.132.249]:42312 "EHLO mail105.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726532AbfHDXyJ (ORCPT ); Sun, 4 Aug 2019 19:54:09 -0400 Received: from dread.disaster.area (pa49-181-167-148.pa.nsw.optusnet.com.au [49.181.167.148]) by mail105.syd.optusnet.com.au (Postfix) with ESMTPS id 734053647B7; Mon, 5 Aug 2019 09:54:06 +1000 (AEST) Received: from dave by dread.disaster.area with local (Exim 4.92) (envelope-from ) id 1huQJ9-0004oa-AA; Mon, 05 Aug 2019 09:52:59 +1000 Date: Mon, 5 Aug 2019 09:52:59 +1000 From: Dave Chinner To: Goldwyn Rodrigues Cc: linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org, hch@lst.de, darrick.wong@oracle.com, ruansy.fnst@cn.fujitsu.com, Goldwyn Rodrigues Subject: Re: [PATCH 02/13] iomap: Read page from srcmap for IOMAP_COW Message-ID: <20190804235259.GD7689@dread.disaster.area> References: <20190802220048.16142-1-rgoldwyn@suse.de> <20190802220048.16142-3-rgoldwyn@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190802220048.16142-3-rgoldwyn@suse.de> User-Agent: Mutt/1.10.1 (2018-07-13) X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.2 cv=FNpr/6gs c=1 sm=1 tr=0 cx=a_idp_d a=gu9DDhuZhshYSb5Zs/lkOA==:117 a=gu9DDhuZhshYSb5Zs/lkOA==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=kj9zAlcOel0A:10 a=FmdZ9Uzk2mMA:10 a=iox4zFpeAAAA:8 a=7-415B0cAAAA:8 a=AMSWgMcbKuDIAMYta8YA:9 a=CjuIK1q_8ugA:10 a=WzC6qhA0u3u7Ye7llzcV:22 a=biEYGPWJfzWAr4FL6Ov7:22 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri, Aug 02, 2019 at 05:00:37PM -0500, Goldwyn Rodrigues wrote: > From: Goldwyn Rodrigues > > In case of a IOMAP_COW, read a page from the srcmap before > performing a write on the page. > > Signed-off-by: Goldwyn Rodrigues > --- > fs/iomap/buffered-io.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index f27756c0b31c..a96cc26eec92 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -581,7 +581,7 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, > > static int > iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags, > - struct page **pagep, struct iomap *iomap) > + struct page **pagep, struct iomap *iomap, struct iomap *srcmap) > { > const struct iomap_page_ops *page_ops = iomap->page_ops; > pgoff_t index = pos >> PAGE_SHIFT; > @@ -607,6 +607,8 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags, > > if (iomap->type == IOMAP_INLINE) > iomap_read_inline_data(inode, page, iomap); > + else if (iomap->type == IOMAP_COW) > + status = __iomap_write_begin(inode, pos, len, page, srcmap); > else if (iomap->flags & IOMAP_F_BUFFER_HEAD) > status = __block_write_begin_int(page, pos, len, NULL, iomap); > else This looks busted w.r.t. IOMAP_F_BUFFER_HEAD. i.e. What's to stop someone returning iomap->type == IOMAP_COW, iomap->flags & IOMAP_F_BUFFER_HEAD? In which case we can't call __iomap_write_begin(), right? I'm with Darrick on CONFIG_IOMAP_DEBUG here - we need to start locking down invalid behaviour and invalid combinations with asserts that tell developers they've broken something. Cheers, Dave. -- Dave Chinner david@fromorbit.com