From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751795AbdFZOyk (ORCPT ); Mon, 26 Jun 2017 10:54:40 -0400 Received: from mail.kernel.org ([198.145.29.99]:55280 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750919AbdFZOyf (ORCPT ); Mon, 26 Jun 2017 10:54:35 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4BC3322B5B 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: Mon, 26 Jun 2017 07:54:33 -0700 From: Jaegeuk Kim To: Chao Yu Cc: linux-kernel@vger.kernel.org, linux-fsdevel@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: <20170626145433.GA8560@jaegeuk-macbookpro.roam.corp.google.com> References: <20170624162522.48931-1-jaegeuk@kernel.org> 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 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? > > 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) > >