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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 D005BC433ED for ; Fri, 2 Apr 2021 19:34:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9FAB661176 for ; Fri, 2 Apr 2021 19:34:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236372AbhDBTej (ORCPT ); Fri, 2 Apr 2021 15:34:39 -0400 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:49126 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S236560AbhDBTeh (ORCPT ); Fri, 2 Apr 2021 15:34:37 -0400 Received: from cwcc.thunk.org (pool-72-74-133-215.bstnma.fios.verizon.net [72.74.133.215]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 132JYEa0017030 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 2 Apr 2021 15:34:14 -0400 Received: by cwcc.thunk.org (Postfix, from userid 15806) id 0628E15C3ACE; Fri, 2 Apr 2021 15:34:14 -0400 (EDT) Date: Fri, 2 Apr 2021 15:34:13 -0400 From: "Theodore Ts'o" To: Jan Kara Cc: linux-fsdevel@vger.kernel.org, Matthew Wilcox , linux-ext4@vger.kernel.org Subject: Re: [PATCH 0/3 RFC] fs: Hole punch vs page cache filling races Message-ID: References: <20210120160611.26853-1-jack@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210120160611.26853-1-jack@suse.cz> Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Wed, Jan 20, 2021 at 05:06:08PM +0100, Jan Kara wrote: > > Amir has reported [1] a that ext4 has a potential issues when reads can race > with hole punching possibly exposing stale data from freed blocks or even > corrupting filesystem when stale mapping data gets used for writeout. The > problem is that during hole punching, new page cache pages can get instantiated > in a punched range after truncate_inode_pages() has run but before the > filesystem removes blocks from the file. In principle any filesystem > implementing hole punching thus needs to implement a mechanism to block > instantiating page cache pages during hole punching to avoid this race. This is > further complicated by the fact that there are multiple places that can > instantiate pages in page cache. We can have regular read(2) or page fault > doing this but fadvise(2) or madvise(2) can also result in reading in page > cache pages through force_page_cache_readahead(). What's the current status of this patch set? I'm going through pending patches and it looks like folks don't like Jan's proposed solution. What are next steps? Thanks, - Ted