From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752326AbdGAImu (ORCPT ); Sat, 1 Jul 2017 04:42:50 -0400 Received: from mail.kernel.org ([198.145.29.99]:35450 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751364AbdGAImr (ORCPT ); Sat, 1 Jul 2017 04:42:47 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BB3F422BC9 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=chao@kernel.org Subject: Re: [f2fs-dev] [PATCH 1/2] f2fs: avoid deadlock caused by lock order of page and lock_op To: Jaegeuk Kim Cc: Chao Yu , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net 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> From: Chao Yu Message-ID: <556d8042-92f3-cb02-26c4-69e89b781c8c@kernel.org> Date: Sat, 1 Jul 2017 16:41:49 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170701072827.GB83795@jaegeuk-macbookpro.roam.corp.google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? 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 >>>