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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A24ADC433F5 for ; Fri, 31 Dec 2021 01:06:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242444AbhLaBGh (ORCPT ); Thu, 30 Dec 2021 20:06:37 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38312 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237396AbhLaBGg (ORCPT ); Thu, 30 Dec 2021 20:06:36 -0500 Received: from mail-ed1-x533.google.com (mail-ed1-x533.google.com [IPv6:2a00:1450:4864:20::533]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4285FC061574 for ; Thu, 30 Dec 2021 17:06:36 -0800 (PST) Received: by mail-ed1-x533.google.com with SMTP id z9so33955121edm.10 for ; Thu, 30 Dec 2021 17:06:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=3yQ0lyfMsNWxiMLxC7em/5nNtO4aymAyCuSjy0PLjqE=; b=SLc0c5KYaStYakowoSGrDCyr+GCKo0gvXAK3yjZoe0eCjK0tvsYkX8SeaOeqLgv+VS rLeF/GiD7XZRyhmcw9sbXDVKeeFFi08zWDH4onV3aJ4ry+5CCLd0uBxfzu6r4ktM6RzF 1NK6NtrifweJfmVuXC/QYhj0g7YvHAd5gPZN9RZbCAnbjuQ9CQSqNbN9D4NPnQc/G1WD 7NNrV6CRid2kEA/D7bTxlDEiyDAHGe54qe6KO+/PDBtEyxMqzDrKkHk5OxYfELyg2sx3 UZpUxupvmLWBQ7JSO3HqaOpa9AbeeURK75MlHGL+LMoRGAUT86pcp38ZCUqIW0jkMt7G X7qA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=3yQ0lyfMsNWxiMLxC7em/5nNtO4aymAyCuSjy0PLjqE=; b=7UbFx7gwughlqCEVVdkJy6oBDsgB64twGPcWp28oYyNf2VocQtjK8wmU6+Cx7rmqLD LpfkfY3q892T0dEstA/0e9ospgUgrZFnYT4tXJhNYxTvrSY8yu0+uotRYMBA44CQqjY3 NIpfLJV8fDKPKPzK0NJ52aMR/w2a5/TWh4wYHwJpEMEsbuR2rWdi8j85mxh/cKso2Emc 6G+w+JVuc80s4UZxCd7vDy9NlZRVZ3xVGJQKtSSjwoaYRT6UBn5nsyYOLkxWzmuUUxpN J2qtE9eX6683S7ToEUNxlc0x1OSfzsJuK8FeZg68IA+q2r/QhB27Lo0PfLzCaIAlGaQ5 KW7A== X-Gm-Message-State: AOAM5301/lsRJh1TTd2TmIko7qiTrDVAzDSFzM7mnhn/+zByd23KK9tG y9mx7RiIfDxsykl7lksdFEpVwNhMfSlOvHJ8FSo= X-Google-Smtp-Source: ABdhPJyo68+ChNlP6cqot2N18ioE6wTAVKtpFUVqJGqbScez/zNRZ8+jd6QXBTq3VXQ5lPT2OuK0PcljVZ21ydATcds= X-Received: by 2002:a17:906:3586:: with SMTP id o6mr27008922ejb.186.1640912794629; Thu, 30 Dec 2021 17:06:34 -0800 (PST) MIME-Version: 1.0 References: <20210903023811.3458-1-chao@kernel.org> In-Reply-To: <20210903023811.3458-1-chao@kernel.org> From: Shachar Raindel Date: Thu, 30 Dec 2021 17:06:23 -0800 Message-ID: Subject: Re: [f2fs-dev] [PATCH] f2fs: quota: fix potential deadlock To: Chao Yu Cc: jaegeuk@kernel.org, linux-kernel@vger.kernel.org, Yi Zhuang , linux-f2fs-devel@lists.sourceforge.net Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Somewhat late to the party (i.e. 3 months late), happy mailbox cleanup holidays! On Thu, Sep 2, 2021 at 8:04 PM Chao Yu wrote: > > As Yi Zhuang reported in bugzilla: > > https://bugzilla.kernel.org/show_bug.cgi?id=214299 > Bug report is for kernel 5.3. When I reported very similar deadlock in google-msm 4.9 tree ( https://lore.kernel.org/linux-f2fs-devel/20201128174124.22397-1-shacharr@gmail.com/t/ ), you pointed out that the code was missing commits which removed the cp_rwsem grabbing (which are also missing from kernel 5.3): commit 435cbab95e3966cd8310addd9e9b758dce0e8b84 Author: Jaegeuk Kim Date: Thu Apr 9 10:25:21 2020 -0700 f2fs: fix quota_sync failure due to f2fs_lock_op commit ca7f76e680745d3b8a386638045f85dac1c4b2f4 Author: Chao Yu Date: Fri May 29 17:29:47 2020 +0800 f2fs: fix wrong discard space commit 79963d967b492876fa17c8c2c2c17b7438683d9b Author: Chao Yu Date: Thu Jun 18 14:36:23 2020 +0800 f2fs: shrink node_write lock coverage Is this patch needed with these commits applied? > > There is potential deadlock during quota data flush as below: > > Thread A: Thread B: > f2fs_dquot_acquire > down_read(&sbi->quota_sem) > f2fs_write_checkpoint > block_operations > f2fs_look_all > down_write(&sbi->cp_rwsem) > f2fs_quota_write > f2fs_write_begin > __do_map_lock > f2fs_lock_op > down_read(&sbi->cp_rwsem) > __need_flush_qutoa > down_write(&sbi->quota_sem) > > This patch changes block_operations() to use trylock, if it fails, > it means there is potential quota data updater, in this condition, > let's flush quota data first and then trylock again to check dirty > status of quota data. > > The side effect is: in heavy race condition (e.g. multi quota data > upaters vs quota data flusher), it may decrease the probability of > synchronizing quota data successfully in checkpoint() due to limited > retry time of quota flush. > > Reported-by: Yi Zhuang > Signed-off-by: Chao Yu As this patch is applied in the mainline kernel, can we CC -stable to get this patch into the various Android kernels? Specifically, https://android.googlesource.com/kernel/msm/+/refs/tags/android-12.0.0_r0.21/fs/f2fs/checkpoint.c#1147 needs this patch (alongside many other google-msm kernel branches). Thanks, --Shachar