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 4F63FC433EF for ; Thu, 3 Feb 2022 14:58:08 +0000 (UTC) Received: from [127.0.0.1] (helo=sfs-ml-4.v29.lw.sourceforge.com) by sfs-ml-4.v29.lw.sourceforge.com with esmtp (Exim 4.94.2) (envelope-from ) id 1nFdYm-0004p7-1P; Thu, 03 Feb 2022 14:58:06 +0000 Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-4.v29.lw.sourceforge.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1nFdYk-0004p1-Rd for linux-f2fs-devel@lists.sourceforge.net; Thu, 03 Feb 2022 14:58:05 +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=neOTmA4TX+ql3GV/bpwz8/t/VmtjHLvdPxnRdt9elLk=; b=OnY6dpEd14GZhZzPi2lm92do5S BZtTGLb+W+FmQ6fUko0esTDm/QqdAmajNVoZPeQLdRVYVXIWiDS5Qj3uK8skPGH+OVRzDIuu/8Qpd mY+Iof+UFakaFVKNOEwL9iCDkfMOuC+jhswUAxBRsCFYWP6mIpc36obzUkwjIcnr8y0c=; 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=neOTmA4TX+ql3GV/bpwz8/t/VmtjHLvdPxnRdt9elLk=; b=Q+xUlrBlqEv2lV21+0wjkCAwjh UlD/1UplZwSTUPjzam8KkMumYAGQMnobQRSOoQMesC97x1p0YXuK06cntnL1oknqMdAXPhUdl2r3A l2IzqikR5rmX7GpuvYaFTYmtXYI7MAYwoV8WXRXqeeDhyRRfdabUeZIEUS71Ig/fF90Q=; Received: from ams.source.kernel.org ([145.40.68.75]) by sfi-mx-2.v28.lw.sourceforge.com with esmtps (TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.94.2) id 1nFdYi-00076K-KG for linux-f2fs-devel@lists.sourceforge.net; Thu, 03 Feb 2022 14:58:05 +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 ams.source.kernel.org (Postfix) with ESMTPS id 68230B8347D; Thu, 3 Feb 2022 14:57:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A3C5AC340E4; Thu, 3 Feb 2022 14:57:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1643900277; bh=Ks22gSDrqIChyIuOe9jWB9tU+82I1HQzBzexKQlVy+8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=JiUudjs7lQELou29GEr4Y4qUOJ4Iq1wQIofGnGMVh96xtnGl2EJqKneLGsCkOTKA9 Vo9BG5fq69h6dcO3Qw/ahzAo7ZjjenKpHhizHDR34CJt1l/rlIqtywMNf2E/gSYAlX dulwcQMyLD04D6QiOdbyZ932Xbt2QuYeqkWUsvUgtCCwYQ2dzRfPEhmucGEXRCW9rC k/cJHweuE4GUA1p/ecYFGI9EDziHQABlhYa1KJR1QdtD0Q+zET0kxJ6pevGG2jhDcb BhLeFhW8AMBJSNdze9p8UW6GssNQTWEmHao/L/zjQWfTerolD5AvIVo+5aH+/O69EL AymmI2cRK/o1Q== Message-ID: <86a175d3-c438-505b-1dbc-4ef6e8b5adcb@kernel.org> Date: Thu, 3 Feb 2022 22:57:51 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Content-Language: en-US To: Jaegeuk Kim References: <20220127054449.24711-1-chao@kernel.org> <51be77f1-6e85-d46d-d0d3-c06d2055a190@kernel.org> From: Chao Yu In-Reply-To: X-Headers-End: 1nFdYi-00076K-KG 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 2022/2/3 9:51, Jaegeuk Kim wrote: > On 01/29, Chao Yu wrote: >> 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? > > I think so. I guess block plug helper says it doesn't allow to use nested plug, so there is only one plug in kworker thread? void blk_start_plug_nr_ios(struct blk_plug *plug, unsigned short nr_ios) { struct task_struct *tsk = current; /* * If this is a nested plug, don't actually assign it. */ if (tsk->plug) return; ... } Thanks, > >> >> 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