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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 7E533C433B4 for ; Tue, 6 Apr 2021 12:17:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 41E3D613BD for ; Tue, 6 Apr 2021 12:17:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343861AbhDFMRM (ORCPT ); Tue, 6 Apr 2021 08:17:12 -0400 Received: from mx2.suse.de ([195.135.220.15]:35868 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243195AbhDFMRL (ORCPT ); Tue, 6 Apr 2021 08:17:11 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 0FE3BB15C; Tue, 6 Apr 2021 12:17:03 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id CDD451F2B77; Tue, 6 Apr 2021 14:17:02 +0200 (CEST) Date: Tue, 6 Apr 2021 14:17:02 +0200 From: Jan Kara To: Theodore Ts'o Cc: Jan Kara , 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: <20210406121702.GB19407@quack2.suse.cz> References: <20210120160611.26853-1-jack@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Fri 02-04-21 15:34:13, Theodore Ts'o wrote: > 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? Note that I did post v2 here: https://lore.kernel.org/linux-fsdevel/20210208163918.7871-1-jack@suse.cz/ It didn't get much comments though. I guess I'll rebase the series, include the explanations I've added in my reply to Dave and resend. Honza -- Jan Kara SUSE Labs, CR