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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 C43D8C2D0E4 for ; Mon, 23 Nov 2020 16:54:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7127520717 for ; Mon, 23 Nov 2020 16:54:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731921AbgKWQyx (ORCPT ); Mon, 23 Nov 2020 11:54:53 -0500 Received: from mx2.suse.de ([195.135.220.15]:54938 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730595AbgKWQyw (ORCPT ); Mon, 23 Nov 2020 11:54:52 -0500 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 4D959AC24; Mon, 23 Nov 2020 16:54:51 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 4D4D21E130F; Mon, 23 Nov 2020 17:54:50 +0100 (CET) Date: Mon, 23 Nov 2020 17:54:50 +0100 From: Jan Kara To: "Theodore Y. Ts'o" Cc: Jan Kara , yebin , jack@suse.com, linux-ext4@vger.kernel.org Subject: Re: [PATCH 0/2] Fix race between do_invalidatepage and init_page_buffers Message-ID: <20201123165450.GL27294@quack2.suse.cz> References: <20200822082218.2228697-1-yebin10@huawei.com> <20200824155143.GH24877@quack2.suse.cz> <5F447351.6060207@huawei.com> <20200825084137.GA32298@quack2.suse.cz> <20201120033600.GA695373@mit.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201120033600.GA695373@mit.edu> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Thu 19-11-20 22:36:00, Theodore Y. Ts'o wrote: > On Tue, Aug 25, 2020 at 10:41:37AM +0200, Jan Kara wrote: > > On Tue 25-08-20 10:11:29, yebin wrote: > > > Your patch certainly can fix the problem with my testcases, but I don't > > > think it's a good way. There are other paths that can call > > > do_invalidatepage , for instance block ioctl to discard and zero_range. > > > > OK, good point! So my patch is a cleanup that stands on its own and we > > should do it regardless. But I agree we need more to completely fix this. > > I don't quite like the callback you've added just for this special case > > (furthermore it grows size of every buffer_head and there can be lots of > > those). But I agree with the general idea that we shouldn't discard buffers > > that the filesystem is working with. > > > > In fact I believe that fallocate(2) and zeroout/discard ioctls should > > return EBUSY if they are run against a mounted device because with 99% > > probability something went wrong and you're accidentally discarding the > > wrong device. But maybe I'm wrong. I'll run this idea through other fs > > developers. > > I'm going through old patches, and I'm trying to figure out where did > we end up on this issue? Did we come to a conclusion on this? Yes, it is fixed by 384d87ef2c95 ("block: Do not discard buffers under a mounted filesystem"). Also the block_write_full_page() got fixed up by 6dbf7bb555981 ("fs: Don't invalidate page buffers in block_write_full_page()"). So we should be all set. > One other thing which I noticed when looking at the original patch was > shouldn't lvreduce not be allowed to run on a LV which has a mounted > file system on its block device? No, that is IMO working by design. The expectation is you can online-shrink the fs and then lvreduce the device... Honza -- Jan Kara SUSE Labs, CR