From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Monakhov Subject: [PATCH 4/4] ext4: serialize truncate with owerwrite DIO workers Date: Tue, 4 Sep 2012 21:22:51 +0400 Message-ID: <1346779371-28203-4-git-send-email-dmonakhov@openvz.org> References: <1346779371-28203-1-git-send-email-dmonakhov@openvz.org> Cc: jack@suse.cz, Dmitry Monakhov To: linux-ext4@vger.kernel.org Return-path: Received: from mail-lb0-f174.google.com ([209.85.217.174]:52139 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757459Ab2IDRXB (ORCPT ); Tue, 4 Sep 2012 13:23:01 -0400 Received: by mail-lb0-f174.google.com with SMTP id gj3so3268369lbb.19 for ; Tue, 04 Sep 2012 10:23:00 -0700 (PDT) In-Reply-To: <1346779371-28203-1-git-send-email-dmonakhov@openvz.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: 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. 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 e696f19..46606e3 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