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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE,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 DFF82C3F2D1 for ; Fri, 6 Mar 2020 00:45:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B493820726 for ; Fri, 6 Mar 2020 00:45:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583455558; bh=fGx37LlA+EG4g7xaMt+UAx7ZpIiPij5CT5m8UDigDpE=; h=Date:From:To:Cc:Subject:List-ID:From; b=sz4jsb4h+YudTgkONDTjjmFd8Z28VbQqOEhB6UiRLTgSlFOO2XemogVFnf3k6Re7h ZDk1je9aOTupwX9OYkXUgMj1gLd4qQPx4p6yUIZSaJF0ypwrOMGrUoldlj3Owm7r5b lGNdjh2G3xREpjDHRHA/sAyqXUjH8jO5wJ263MqY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726243AbgCFAp5 (ORCPT ); Thu, 5 Mar 2020 19:45:57 -0500 Received: from mail.kernel.org ([198.145.29.99]:53126 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726184AbgCFAp5 (ORCPT ); Thu, 5 Mar 2020 19:45:57 -0500 Received: from gmail.com (unknown [104.132.1.77]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DD56E2070E; Fri, 6 Mar 2020 00:45:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583455557; bh=fGx37LlA+EG4g7xaMt+UAx7ZpIiPij5CT5m8UDigDpE=; h=Date:From:To:Cc:Subject:From; b=MW4Vk6JvFjyAkqLILduCSVnHoFDTP44wh8BDtkn3mMCcS3QOVTbqORQOYyHbCVBo6 QB7uLmdz+7k/bhThcepfO6I4noScDXO4lwBfZrbsjO7nJq/F7DXS/DLq9PNlIrm/0Y LUoljjpLlpCbARZKFMZ3rRkGhG9eAYDUb82nAOiM= Date: Thu, 5 Mar 2020 16:45:55 -0800 From: Eric Biggers To: linux-fsdevel@vger.kernel.org Cc: linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Subject: lazytime causing inodes to remain dirty after sync? Message-ID: <20200306004555.GB225345@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.12.2 (2019-09-21) Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org While testing my patch "fscrypt: don't evict dirty inodes after removing key" (https://lkml.kernel.org/r/20200305084138.653498-1-ebiggers@kernel.org), I've run into an issue where even after the filesystem is sync'ed and no files are in-use, inodes can remain dirty if the filesystem is mounted with -o lazytime. Thus, my patch causes some inodes to not be evicted when they should be. (lazytime is the default on f2fs, but ext4 supports it too.) This is caused by the following code in __writeback_single_inode() that redirties the inode if its access time is dirty: if (dirty & I_DIRTY_TIME) mark_inode_dirty_sync(inode); /* Don't write the inode if only I_DIRTY_PAGES was set */ if (dirty & ~I_DIRTY_PAGES) { int err = write_inode(inode, wbc); if (ret == 0) ret = err; } trace_writeback_single_inode(inode, wbc, nr_to_write); return ret; Here's a reproducer in the kvm-xfstests test appliance which demonstrates the problem using sync(), without fscrypt involved at all: sysctl vm.dirty_expire_centisecs=500 umount /vdc mkfs.ext4 -F /dev/vdc mount /vdc -o lazytime echo contents > /vdc/file sync ino=$(stat -c %i /vdc/file) echo 1 | tee /sys/kernel/debug/tracing/events/writeback/writeback_{single_inode_start,mark_inode_dirty,lazytime}/enable echo "ino == $ino" | tee /sys/kernel/debug/tracing/events/writeback/writeback_{single_inode_start,mark_inode_dirty,lazytime}/filter echo > /sys/kernel/debug/tracing/trace cat /vdc/file > /dev/null sync cat /sys/kernel/debug/tracing/trace_pipe The tracing shows that the inode for /vdc/file is written during the sync at 7.28s. But then, still during the sync, it's immediately re-dirtied. It then gets written again later in the background, after the sync. cat-286 [001] ...1 7.279433: writeback_mark_inode_dirty: bdi 254:32: ino=12 state= flags=I_DIRTY_TIME kworker/u8:0-8 [003] ...1 7.282647: writeback_single_inode_start: bdi 254:32: ino=12 state=I_SYNC|I_DIRTY_TIME|I_DIRTY_TIME_EXPIRED dirtied_when=4294879420 age=0 index=1 to_write=9223372036854775807 wrote=0 cgroup_ino=1 kworker/u8:0-8 [003] ...2 7.282660: writeback_lazytime: dev 254,32 ino 12 dirtied 4294879420 state I_SYNC|I_DIRTY_TIME|I_DIRTY_TIME_EXPIRED mode 0100644 kworker/u8:0-8 [003] ...1 7.283204: writeback_mark_inode_dirty: bdi 254:32: ino=12 state=I_SYNC flags=I_DIRTY_SYNC kworker/u8:0-8 [003] ...1 12.412079: writeback_single_inode_start: bdi 254:32: ino=12 state=I_DIRTY_SYNC|I_SYNC dirtied_when=4294879421 age=5 index=1 to_write=13312 wrote=0 cgroup_ino=1 Is this behavior intentional at all? It seems like a bug; it seems the inode should be written just once, during the sync. - Eric