From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751388AbdFZIQR (ORCPT ); Mon, 26 Jun 2017 04:16:17 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:8849 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751353AbdFZIQL (ORCPT ); Mon, 26 Jun 2017 04:16:11 -0400 Subject: Re: [f2fs-dev] [PATCH 1/2] f2fs: avoid deadlock caused by lock order of page and lock_op To: Jaegeuk Kim , , , References: <20170624162522.48931-1-jaegeuk@kernel.org> From: Chao Yu Message-ID: Date: Mon, 26 Jun 2017 16:15:41 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.0 MIME-Version: 1.0 In-Reply-To: <20170624162522.48931-1-jaegeuk@kernel.org> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.134.22.195] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020205.5950C2B3.0088,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2014-11-16 11:51:01, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 00fd59f2b057a99e99e0624eb1851b79 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jaegeuk, On 2017/6/25 0:25, Jaegeuk Kim wrote: > - punch_hole > - fill_zero > - f2fs_lock_op > - get_new_data_page > - lock_page > > - f2fs_write_data_pages > - lock_page > - do_write_data_page > - f2fs_lock_op Good catch! With this implementation, page writeback can fail due to concurrent checkpoint, this will make fsync/atomic_commit which trigger synchronous write failed randomly. How about unifying the lock order in punch_hole as one in writepages for regular inode? We can add one more parameter in get_new_data_page to indicate whether callee needs to lock cp_rwsem. Thanks, > > Signed-off-by: Jaegeuk Kim > --- > fs/f2fs/data.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c > index 7d3af48d34a9..9141bd19a902 100644 > --- a/fs/f2fs/data.c > +++ b/fs/f2fs/data.c > @@ -1404,8 +1404,9 @@ int do_write_data_page(struct f2fs_io_info *fio) > } > } > > - if (fio->need_lock == LOCK_REQ) > - f2fs_lock_op(fio->sbi); > + /* Deadlock due to between page->lock and f2fs_lock_op */ > + if (fio->need_lock == LOCK_REQ && !f2fs_trylock_op(fio->sbi)) > + return -EAGAIN; > > err = get_dnode_of_data(&dn, page->index, LOOKUP_NODE); > if (err) >