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 A920DC433EF for ; Sat, 29 Jan 2022 01:48:48 +0000 (UTC) Received: from [127.0.0.1] (helo=sfs-ml-1.v29.lw.sourceforge.com) by sfs-ml-1.v29.lw.sourceforge.com with esmtp (Exim 4.94.2) (envelope-from ) id 1nDcr9-0002ga-Ks; Sat, 29 Jan 2022 01:48:46 +0000 Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-1.v29.lw.sourceforge.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1nDcr7-0002gR-KL for linux-f2fs-devel@lists.sourceforge.net; Sat, 29 Jan 2022 01:48:44 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: From:References:Cc:To:Subject:MIME-Version:Date:Message-ID:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=zBxg9d58hWe5sn94UEXZN15TG2oWBqYGjSWto5X/voY=; b=mS24FniI4KhTTLNw03W9drVEFu l5KjBAYOiCYvu1aiEhBIZetmmeZitKtWaEDwsoKT9jQy0F/5exTFrbhnjny0Ai4kA1/CiguljCXiL LNajw/E4bf4uAa+v9UoRS2YdCni97ptPSvGuf+dcxFmgjdnRGXaY28Vtj+2h5bh92RLw=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:From:References:Cc:To: Subject:MIME-Version:Date:Message-ID:Sender:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=zBxg9d58hWe5sn94UEXZN15TG2oWBqYGjSWto5X/voY=; b=hSMgo25qN67Z2WkYJG08TD6ZW+ dQ+XTjCE+1d0aBCDHxYolXNy8isIGl0agERRWLQJW765uRtpCpJVl91iF6HfzEBZwXV0nbyDqTkdv vZplo5SVSqsgG8ougMlbM9dMihbQYe8mlWHIld6upab/L20LqIwKDM5kbMX5kxsCJM8o=; Received: from dfw.source.kernel.org ([139.178.84.217]) by sfi-mx-1.v28.lw.sourceforge.com with esmtps (TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.94.2) id 1nDcr5-001hcr-88 for linux-f2fs-devel@lists.sourceforge.net; Sat, 29 Jan 2022 01:48:43 +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 D98E3616C5; Sat, 29 Jan 2022 01:48:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D8ED7C340E7; Sat, 29 Jan 2022 01:48:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1643420909; bh=U4yFyHtwMRnXHRamWfKkGK76Ozd5kjk/jL2nRTJ0Woc=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=SgNJ3wxqNsT4ys0KRFXW4k41B8pB08uCH0tVI4di5yabwdCTREf6UR8U3YVnWOnRN OaMYcSVV6XZgxuZVvy+UemvsuJm6bBHqiVdbIZ5HW4CZ3FyNUEVeztVFgLcn7T2eYI mM7G8NB0LtN/N6yiAdoViAs0oGQGXs0kTr1YDnvtPvkb9Mad2HbQBx5JW20dwia7F+ x2ZY8bOYokrqC0lUp8Vabw1gwIPPRN6BtDYYivhh5uSbilMRGfCWNGQ7iLIjEMkxsa ZPVOSxe0T8yNk8YIGX7jNeeiiGyDHyst45goYYlyuMdQB/OqdlMXiEbjyLLLOdj52j dT3/wrLvV/B/w== Message-ID: <51be77f1-6e85-d46d-d0d3-c06d2055a190@kernel.org> Date: Sat, 29 Jan 2022 09:48:25 +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 Content-Language: en-US To: Jaegeuk Kim References: <20220127054449.24711-1-chao@kernel.org> From: Chao Yu In-Reply-To: X-Headers-End: 1nDcr5-001hcr-88 Subject: Re: [f2fs-dev] [PATCH] f2fs: fix to avoid 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: Jing Xia , Zhiguo Niu , linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On 2022/1/29 8:37, Jaegeuk Kim wrote: > On 01/28, Chao Yu wrote: >> 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)? > > Wasn't that added into a different task->plug? I'm not sure I've got your concern correctly... Do you mean NodeA and other IOs from do_writepages() were plugged in different local plug variables? Thanks, > >> >> 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 _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel