From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kara Subject: Re: [PATCH 03/12] ext4: Remove bogus wait for unwritten extents in ext4_ind_direct_IO Date: Tue, 22 Jan 2013 16:21:17 +0100 Message-ID: <20130122152117.GA32366@quack.suse.cz> References: <1358510446-19174-1-git-send-email-jack@suse.cz> <1358510446-19174-4-git-send-email-jack@suse.cz> <87k3r5qxpf.fsf@openvz.org> <20130122134400.GB28331@quack.suse.cz> <87ehhdqpbd.fsf@openvz.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kara , Ted Tso , linux-ext4@vger.kernel.org To: Dmitry Monakhov Return-path: Received: from cantor2.suse.de ([195.135.220.15]:56141 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754531Ab3AVPVV (ORCPT ); Tue, 22 Jan 2013 10:21:21 -0500 Content-Disposition: inline In-Reply-To: <87ehhdqpbd.fsf@openvz.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Tue 22-01-13 18:12:38, Dmitry Monakhov wrote: > On Tue, 22 Jan 2013 14:44:00 +0100, Jan Kara wrote: > > On Tue 22-01-13 15:11:24, Dmitry Monakhov wrote: > > > On Fri, 18 Jan 2013 13:00:37 +0100, Jan Kara wrote: > > > > When using indirect blocks there is no possibility to have any unwritten > > > > extents. So wait for them in ext4_ind_direct_IO() is just bogus. > > > But as soon as i remember indirect implementation may also be used by > > > extents based inodes 3074: ext4_ext_direct_IO > > > /* Use the old path for reads and writes beyond i_size. */ > > > if (rw != WRITE || final_size > inode->i_size) > > > return ext4_ind_direct_IO(rw, iocb, iov, offset, nr_segs); > > > > > > Am I missing ? > > Ah, that's a catch. Thanks for pointing that out! So my patch is wrong > > and that code path needs some cleaning and commenting. In particular I'm > > afraid using dioread_nolock for inodes with indirect map causes data > > exposure bugs when unlocked DIO read races with DIO write because such > > inodes don't support uninitialized extents. > Yes that's why dioread_nolock works only for extent based inodes > > static inline int ext4_should_dioread_nolock(struct inode *inode) > { > if (!test_opt(inode->i_sb, DIOREAD_NOLOCK)) > return 0; > if (!S_ISREG(inode->i_mode)) > return 0; > if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) > return 0; > if (ext4_should_journal_data(inode)) > return 0; > return 1; > } Sure, I was confused. Things work correctly just the code flow is a bit confusing. Honza -- Jan Kara SUSE Labs, CR