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 9DD7DC433F5 for ; Fri, 28 Jan 2022 01:43:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344745AbiA1Bnf (ORCPT ); Thu, 27 Jan 2022 20:43:35 -0500 Received: from ams.source.kernel.org ([145.40.68.75]:35652 "EHLO ams.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230132AbiA1Bnd (ORCPT ); Thu, 27 Jan 2022 20:43:33 -0500 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 ams.source.kernel.org (Postfix) with ESMTPS id 93F95B82104 for ; Fri, 28 Jan 2022 01:43:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E5EE5C340E5; Fri, 28 Jan 2022 01:43:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1643334211; bh=TkowqnMfrmwTAcJsGdAvnwq3afg44JpFf1XwkrSPxKo=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=hk6QOu3rIsQHhDpi2BCWY+cWfyR/YNeg4e14onaDxvIPcbSf2AGlf6qAnUhxUskl2 1iIsNbwPzfnA/Ttdlirbmi3GsOJdNzX7LuUfl88RP6Sq7tn2yQpQZDJ4SBijNbAmU3 IK3JxXuC997DZTyXuJRHX0S+0aA2EYth82qNVwAOjQj44AZSiNXG2LoDiXUl8vg9Sp YotnMNzAgoaTGyed/vkSusyudJwKrdsNx+4K9MfN+2m6LDwlTSthZZHj2WDNsjTrQ+ +cL1+ehElCCAzQYHLYZ/hiM7XIqKT7VUWB3T+tGAU++CQqPVBfIAfwluMRpSMsojwF gIEn1fqnm5ZLA== Message-ID: Date: Fri, 28 Jan 2022 09:43:27 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.4.1 Subject: Re: [PATCH] f2fs: fix to avoid potential deadlock Content-Language: en-US To: Jaegeuk Kim Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, Zhiguo Niu , Jing Xia References: <20220127054449.24711-1-chao@kernel.org> From: Chao Yu In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/1/28 5:59, Jaegeuk Kim wrote: > On 01/27, Chao Yu wrote: >> Quoted from Jing Xia's report, there is a potential deadlock may happen >> between kworker and checkpoint as below: >> >> [T:writeback] [T:checkpoint] >> - wb_writeback >> - blk_start_plug >> bio contains NodeA was plugged in writeback threads > > I'm still trying to understand more precisely. So, how is it possible to > have bio having node write in this current context? IMO, after above blk_start_plug(), it may plug some inode's node page in kworker during writebacking node_inode's data page (which should be node page)? Thanks, > >> - do_writepages -- sync write inodeB, inc wb_sync_req[DATA] >> - f2fs_write_data_pages >> - f2fs_write_single_data_page -- write last dirty page >> - f2fs_do_write_data_page >> - set_page_writeback -- clear page dirty flag and >> PAGECACHE_TAG_DIRTY tag in radix tree >> - f2fs_outplace_write_data >> - f2fs_update_data_blkaddr >> - f2fs_wait_on_page_writeback -- wait NodeA to writeback here >> - inode_dec_dirty_pages >> - writeback_sb_inodes >> - writeback_single_inode >> - do_writepages >> - f2fs_write_data_pages -- skip writepages due to wb_sync_req[DATA] >> - wbc->pages_skipped += get_dirty_pages() -- PAGECACHE_TAG_DIRTY is not set but get_dirty_pages() returns one >> - requeue_inode -- requeue inode to wb->b_dirty queue due to non-zero.pages_skipped >> - blk_finish_plug >> >> Let's try to avoid deadlock condition by forcing unplugging previous bio via >> blk_finish_plug(current->plug) once we'v skipped writeback in writepages() >> due to valid sbi->wb_sync_req[DATA/NODE]. >> >> Fixes: 687de7f1010c ("f2fs: avoid IO split due to mixed WB_SYNC_ALL and WB_SYNC_NONE") >> Signed-off-by: Zhiguo Niu >> Signed-off-by: Jing Xia >> Signed-off-by: Chao Yu >> --- >> fs/f2fs/data.c | 6 +++++- >> fs/f2fs/node.c | 6 +++++- >> 2 files changed, 10 insertions(+), 2 deletions(-) >> >> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c >> index 76d6fe7b0c8f..932a4c81acaf 100644 >> --- a/fs/f2fs/data.c >> +++ b/fs/f2fs/data.c >> @@ -3174,8 +3174,12 @@ static int __f2fs_write_data_pages(struct address_space *mapping, >> /* to avoid spliting IOs due to mixed WB_SYNC_ALL and WB_SYNC_NONE */ >> if (wbc->sync_mode == WB_SYNC_ALL) >> atomic_inc(&sbi->wb_sync_req[DATA]); >> - else if (atomic_read(&sbi->wb_sync_req[DATA])) >> + else if (atomic_read(&sbi->wb_sync_req[DATA])) { >> + /* to avoid potential deadlock */ >> + if (current->plug) >> + blk_finish_plug(current->plug); >> goto skip_write; >> + } >> >> if (__should_serialize_io(inode, wbc)) { >> mutex_lock(&sbi->writepages); >> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c >> index 556fcd8457f3..69c6bcaf5aae 100644 >> --- a/fs/f2fs/node.c >> +++ b/fs/f2fs/node.c >> @@ -2106,8 +2106,12 @@ static int f2fs_write_node_pages(struct address_space *mapping, >> >> if (wbc->sync_mode == WB_SYNC_ALL) >> atomic_inc(&sbi->wb_sync_req[NODE]); >> - else if (atomic_read(&sbi->wb_sync_req[NODE])) >> + else if (atomic_read(&sbi->wb_sync_req[NODE])) { >> + /* to avoid potential deadlock */ >> + if (current->plug) >> + blk_finish_plug(current->plug); >> goto skip_write; >> + } >> >> trace_f2fs_writepages(mapping->host, wbc, NODE); >> >> -- >> 2.32.0