From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kara Subject: Re: [PATCH 4/4] ext4: serialize truncate with owerwrite DIO workers Date: Wed, 5 Sep 2012 17:49:20 +0200 Message-ID: <20120905154920.GF18051@quack.suse.cz> References: <1346780214-29845-1-git-send-email-dmonakhov@openvz.org> <1346780214-29845-4-git-send-email-dmonakhov@openvz.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4@vger.kernel.org, jack@suse.cz To: Dmitry Monakhov Return-path: Received: from cantor2.suse.de ([195.135.220.15]:49064 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751999Ab2IEPtW (ORCPT ); Wed, 5 Sep 2012 11:49:22 -0400 Content-Disposition: inline In-Reply-To: <1346780214-29845-4-git-send-email-dmonakhov@openvz.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Tue 04-09-12 21:36:54, Dmitry Monakhov wrote: > Jan Kara have spotted interesting issue: > There are potential data corruption issue with direct IO overwrites > racing with truncate: > Like: > dio write truncate_task > ->ext4_ext_direct_IO > ->overwrite == 1 > ->down_read(&EXT4_I(inode)->i_data_sem); > ->mutex_unlock(&inode->i_mutex); > ->ext4_setattr() > ->inode_dio_wait() > ->truncate_setsize() > ->ext4_truncate() > ->down_write(&EXT4_I(inode)->i_data_sem); > ->__blockdev_direct_IO > ->ext4_get_block > ->submit_io() > ->up_read(&EXT4_I(inode)->i_data_sem); > # truncate data blocks, allocate them to > # other inode - bad stuff happens because > # dio is still in flight. > > In order to serialize with truncate dio worker should grab extra i_dio_count > reference before drop i_mutex. Thanks for the patch. You can add: Reviewed-by: Jan Kara Honza > Signed-off-by: Dmitry Monakhov > --- > fs/ext4/inode.c | 2 ++ > 1 files changed, 2 insertions(+), 0 deletions(-) > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index 5a75908..9725acb 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -3035,6 +3035,7 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb, > overwrite = *((int *)iocb->private); > > if (overwrite) { > + atomic_inc(&inode->i_dio_count); > down_read(&EXT4_I(inode)->i_data_sem); > mutex_unlock(&inode->i_mutex); > } > @@ -3134,6 +3135,7 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb, > if (overwrite) { > up_read(&EXT4_I(inode)->i_data_sem); > mutex_lock(&inode->i_mutex); > + inode_dio_done(inode); > } > > return ret; > -- > 1.7.7.6 > -- Jan Kara SUSE Labs, CR