From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752407AbdGED2h (ORCPT ); Tue, 4 Jul 2017 23:28:37 -0400 Received: from mail.kernel.org ([198.145.29.99]:51562 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752286AbdGED2f (ORCPT ); Tue, 4 Jul 2017 23:28:35 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DD70A22C7D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=jaegeuk@kernel.org Date: Tue, 4 Jul 2017 20:28:34 -0700 From: Jaegeuk Kim To: Chao Yu Cc: Chao Yu , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Subject: Re: [f2fs-dev] [PATCH 1/2] f2fs: avoid deadlock caused by lock order of page and lock_op Message-ID: <20170705032834.GA15448@jaegeuk-macbookpro.roam.corp.google.com> References: <20170624162522.48931-1-jaegeuk@kernel.org> <20170626145433.GA8560@jaegeuk-macbookpro.roam.corp.google.com> <060e5c2d-50cd-9f76-9efc-0cdec0d3df3b@kernel.org> <20170701072827.GB83795@jaegeuk-macbookpro.roam.corp.google.com> <556d8042-92f3-cb02-26c4-69e89b781c8c@kernel.org> <20170701142722.GA901@jaegeuk-macbookpro.roam.corp.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.8.2 (2017-04-18) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/05, Chao Yu wrote: > On 2017/7/1 22:27, Jaegeuk Kim wrote: > > On 07/01, Chao Yu wrote: > >> On 2017/7/1 15:28, Jaegeuk Kim wrote: > >>> On 06/26, Chao Yu wrote: > >>>> Hi Jaegeuk, > >>>> > >>>> On 2017/6/26 22:54, Jaegeuk Kim wrote: > >>>>> Hi Chao, > >>>>> > >>>>> On 06/26, Chao Yu wrote: > >>>>>> 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. > >>>>> > >>>>> Currently, there would be some places to keep cp_rwsem -> page.lock, which seems > >>>>> not simple to change the lock order with page.lock -> cp_rwsem. IMO, we can retry > >>>>> flushing data in f2fs_sync_file, once it gets -EAGAIN. > >>>>> > >>>>> Any thoughts? > >>>> > >>>> What about adding inode_lock in f2fs_sync_file to exclude other > >>>> foreground operation which have reversed lock order? Atomic_commit is OK > >>>> since it has inode_lock in its path. > >>> > >>> I have concerned about performance regression, if we do that. > >> > >> I think fsync vs write or fsync vs fsync scenarios are unusual, so is > >> there any usecase? > > > > Well, that'd be common to call multiple fsync calls at the same time. > > Like dbench or tiotest? > > Do you have test numbers of dbench/tiotest with inode:lock in fsync? No, do we need? > > Thanks, > > > > >> > >> Thanks, > >> > >>> > >>>> > >>>> Thanks, > >>>> > >>>>> > >>>>>> > >>>>>> 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) > >>>>>>> > >>>>> > >>>>> ------------------------------------------------------------------------------ > >>>>> Check out the vibrant tech community on one of the world's most > >>>>> engaging tech sites, Slashdot.org! http://sdm.link/slashdot > >>>>> _______________________________________________ > >>>>> Linux-f2fs-devel mailing list > >>>>> Linux-f2fs-devel@lists.sourceforge.net > >>>>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel > >>>>>