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 C22F0C433EF for ; Wed, 5 Jan 2022 15:01:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233942AbiAEPBp (ORCPT ); Wed, 5 Jan 2022 10:01:45 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49644 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241175AbiAEPBo (ORCPT ); Wed, 5 Jan 2022 10:01:44 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9D18BC061245 for ; Wed, 5 Jan 2022 07:01:44 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 3AE926178E for ; Wed, 5 Jan 2022 15:01:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 11A23C36AE3; Wed, 5 Jan 2022 15:01:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1641394903; bh=CD89Bk4p1/Y++Rnwm7lJnL3hwXMixERyPrxxV9HwqIQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=KJAkbj0mHkka3crRuvSFpNd3Av83nJ13NMsUI571Id4ZACnXqMU28BRLbX2dWtwaU 14V0upTnn2+NbBQjJwtXzOY5qkEHmokPNGYJt97lWbqapsfQo/l/9b1Fzv3mLmSz6p k324HYaW538QvA0oa4SDhJFPfq5yHNuKgABPoY9M= Date: Wed, 5 Jan 2022 16:01:40 +0100 From: Greg KH To: Chao Yu Cc: stable@vger.kernel.org, jaegeuk@kernel.org, linux-f2fs-devel@lists.sourceforge.net, Yi Zhuang Subject: Re: [PATCH] f2fs: quota: fix potential deadlock Message-ID: References: <20220104130513.3077-1-chao@kernel.org> <53d75d26-2289-a66a-a7fa-62593bad81c8@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Tue, Jan 04, 2022 at 11:48:25PM +0800, Chao Yu wrote: > On 2022/1/4 23:17, Greg KH wrote: > > On Tue, Jan 04, 2022 at 11:05:36PM +0800, Chao Yu wrote: > > > On 2022/1/4 21:18, Greg KH wrote: > > > > On Tue, Jan 04, 2022 at 09:05:13PM +0800, Chao Yu wrote: > > > > > commit a5c0042200b28fff3bde6fa128ddeaef97990f8d upstream. > > > > > > > > > > As Yi Zhuang reported in bugzilla: > > > > > > > > > > https://bugzilla.kernel.org/show_bug.cgi?id=214299 > > > > > > > > > > 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. > > > > > > > > > > Fixes: db6ec53b7e03 ("f2fs: add a rw_sem to cover quota flag changes") > > > > > Cc: stable@vger.kernel.org # v5.3+ > > > > > Reported-by: Yi Zhuang > > > > > Signed-off-by: Chao Yu > > > > > Signed-off-by: Jaegeuk Kim > > > > > --- > > > > > fs/f2fs/checkpoint.c | 3 ++- > > > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > > > > > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c > > > > > index 83e9bc0f91ff..7b0282724231 100644 > > > > > --- a/fs/f2fs/checkpoint.c > > > > > +++ b/fs/f2fs/checkpoint.c > > > > > @@ -1162,7 +1162,8 @@ static bool __need_flush_quota(struct f2fs_sb_info *sbi) > > > > > if (!is_journalled_quota(sbi)) > > > > > return false; > > > > > - down_write(&sbi->quota_sem); > > > > > + if (!down_write_trylock(&sbi->quota_sem)) > > > > > + return true; > > > > > if (is_sbi_flag_set(sbi, SBI_QUOTA_SKIP_FLUSH)) { > > > > > ret = false; > > > > > } else if (is_sbi_flag_set(sbi, SBI_QUOTA_NEED_REPAIR)) { > > > > > -- > > > > > 2.32.0 > > > > > > > > > > > > > What stable tree(s) is this for? > > > > > > Oh, please help to try applying to 5.4, 5.10, and 5.15 stable trees, thanks! > > > > This is already in the 5.15.6 kernel release, do you need it applied > > there again? :) > > Oops, no, so 5.4 and 5.10 is enough. ;) > We can skip 5.15 since this patch was merged in 5.15-rc1 at the first time. It was merged in 5.16-rc1, and then backported to 5.15.6. You might want to check your git scripts. Anyway, now queued up, thanks. greg k-h 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 lists.sourceforge.net (lists.sourceforge.net [216.105.38.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B5DB6C433F5 for ; Wed, 5 Jan 2022 15:02:05 +0000 (UTC) Received: from [127.0.0.1] (helo=sfs-ml-2.v29.lw.sourceforge.com) by sfs-ml-2.v29.lw.sourceforge.com with esmtp (Exim 4.94.2) (envelope-from ) id 1n57ng-00005P-0j; Wed, 05 Jan 2022 15:02:04 +0000 Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-2.v29.lw.sourceforge.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1n57ne-00005G-66 for linux-f2fs-devel@lists.sourceforge.net; Wed, 05 Jan 2022 15:02:02 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; 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b=iZiSRq8OyTVA/SFwxRTvo0ZqV7 zcHFIkhu7zbB+Rd21Iq2Moq/YhKE+dl1pPvEnH9oQXciavVn4nP2KUQVQrCwy+0EiFWNVZK/Tx4RI jRIgwOzIYWgf+1rKLSw2mPIhTulLJUfnjRgu0uFRw3H4GMT+Q66C+L2XetlMNibuVfZQ=; Received: from dfw.source.kernel.org ([139.178.84.217]) by sfi-mx-2.v28.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.92.3) id 1n57nW-0008RX-D2 for linux-f2fs-devel@lists.sourceforge.net; Wed, 05 Jan 2022 15:02:02 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 3898561771; Wed, 5 Jan 2022 15:01:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 11A23C36AE3; Wed, 5 Jan 2022 15:01:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1641394903; bh=CD89Bk4p1/Y++Rnwm7lJnL3hwXMixERyPrxxV9HwqIQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=KJAkbj0mHkka3crRuvSFpNd3Av83nJ13NMsUI571Id4ZACnXqMU28BRLbX2dWtwaU 14V0upTnn2+NbBQjJwtXzOY5qkEHmokPNGYJt97lWbqapsfQo/l/9b1Fzv3mLmSz6p k324HYaW538QvA0oa4SDhJFPfq5yHNuKgABPoY9M= Date: Wed, 5 Jan 2022 16:01:40 +0100 From: Greg KH To: Chao Yu Message-ID: References: <20220104130513.3077-1-chao@kernel.org> <53d75d26-2289-a66a-a7fa-62593bad81c8@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Headers-End: 1n57nW-0008RX-D2 Subject: Re: [f2fs-dev] [PATCH] f2fs: quota: fix potential deadlock X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: jaegeuk@kernel.org, Yi Zhuang , stable@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On Tue, Jan 04, 2022 at 11:48:25PM +0800, Chao Yu wrote: > On 2022/1/4 23:17, Greg KH wrote: > > On Tue, Jan 04, 2022 at 11:05:36PM +0800, Chao Yu wrote: > > > On 2022/1/4 21:18, Greg KH wrote: > > > > On Tue, Jan 04, 2022 at 09:05:13PM +0800, Chao Yu wrote: > > > > > commit a5c0042200b28fff3bde6fa128ddeaef97990f8d upstream. > > > > > > > > > > As Yi Zhuang reported in bugzilla: > > > > > > > > > > https://bugzilla.kernel.org/show_bug.cgi?id=214299 > > > > > > > > > > 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. > > > > > > > > > > Fixes: db6ec53b7e03 ("f2fs: add a rw_sem to cover quota flag changes") > > > > > Cc: stable@vger.kernel.org # v5.3+ > > > > > Reported-by: Yi Zhuang > > > > > Signed-off-by: Chao Yu > > > > > Signed-off-by: Jaegeuk Kim > > > > > --- > > > > > fs/f2fs/checkpoint.c | 3 ++- > > > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > > > > > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c > > > > > index 83e9bc0f91ff..7b0282724231 100644 > > > > > --- a/fs/f2fs/checkpoint.c > > > > > +++ b/fs/f2fs/checkpoint.c > > > > > @@ -1162,7 +1162,8 @@ static bool __need_flush_quota(struct f2fs_sb_info *sbi) > > > > > if (!is_journalled_quota(sbi)) > > > > > return false; > > > > > - down_write(&sbi->quota_sem); > > > > > + if (!down_write_trylock(&sbi->quota_sem)) > > > > > + return true; > > > > > if (is_sbi_flag_set(sbi, SBI_QUOTA_SKIP_FLUSH)) { > > > > > ret = false; > > > > > } else if (is_sbi_flag_set(sbi, SBI_QUOTA_NEED_REPAIR)) { > > > > > -- > > > > > 2.32.0 > > > > > > > > > > > > > What stable tree(s) is this for? > > > > > > Oh, please help to try applying to 5.4, 5.10, and 5.15 stable trees, thanks! > > > > This is already in the 5.15.6 kernel release, do you need it applied > > there again? :) > > Oops, no, so 5.4 and 5.10 is enough. ;) > We can skip 5.15 since this patch was merged in 5.15-rc1 at the first time. It was merged in 5.16-rc1, and then backported to 5.15.6. You might want to check your git scripts. Anyway, now queued up, thanks. greg k-h _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel