From: Zheng Liu <gnehzuil.liu@gmail.com>
To: Jan Kara <jack@suse.cz>
Cc: Dmitry Monakhov <dmonakhov@openvz.org>, Ted Tso <tytso@mit.edu>,
linux-ext4@vger.kernel.org
Subject: Re: [PATCH 03/12] ext4: Remove bogus wait for unwritten extents in ext4_ind_direct_IO
Date: Wed, 23 Jan 2013 00:00:17 +0800 [thread overview]
Message-ID: <20130122160017.GA2072@gmail.com> (raw)
In-Reply-To: <20130122152243.GB32366@quack.suse.cz>
On Tue, Jan 22, 2013 at 04:22:43PM +0100, Jan Kara wrote:
> On Tue 22-01-13 22:22:21, Zheng Liu wrote:
> > On Tue, Jan 22, 2013 at 02:44:00PM +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 <jack@suse.cz> 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.
> >
> > Sorry, but I am still confused. dioread_nolock is only for extent-based
> > file. So when a file system without extent feature, dioread_nolock
> > couldn't be enabled. It seems that we don't need to worry about
> > exposing stale data here.
> Well, you can have fs with extent feature enabled but still with inodes
> using indirect map. But as Dmitry pointed out, ext4_should_dioread_nolock()
> handles that correctly. So there's not a bug I was suspecting.
Yep, the patch itself is fine. But that would be great if a comment is
added here.
Regards,
- Zheng
next prev parent reply other threads:[~2013-01-22 15:46 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-18 12:00 [PATCH 0/12 v2] ext4: Several simplifications and fixes Jan Kara
2013-01-18 12:00 ` [PATCH 01/12] ext4: Always use ext4_bio_write_page() for writeout Jan Kara
2013-01-28 14:31 ` Theodore Ts'o
2013-01-18 12:00 ` [PATCH 02/12] ext4: Use redirty_page_for_writepage() in ext4_bio_write_page() Jan Kara
2013-01-28 14:34 ` Theodore Ts'o
2013-01-18 12:00 ` [PATCH 03/12] ext4: Remove bogus wait for unwritten extents in ext4_ind_direct_IO Jan Kara
2013-01-22 11:11 ` Dmitry Monakhov
2013-01-22 13:44 ` Jan Kara
2013-01-22 14:12 ` Dmitry Monakhov
2013-01-22 15:21 ` Jan Kara
2013-01-22 14:22 ` Zheng Liu
2013-01-22 15:22 ` Jan Kara
2013-01-22 16:00 ` Zheng Liu [this message]
2013-01-22 23:14 ` Jan Kara
2013-01-23 6:11 ` Zheng Liu
2013-01-23 9:42 ` Jan Kara
2013-01-18 12:00 ` [PATCH 04/12] ext4: Disable merging of uninitialized extents Jan Kara
2013-01-24 9:49 ` Dmitry Monakhov
2013-01-24 15:12 ` Jan Kara
2013-01-24 15:32 ` Dmitry Monakhov
2013-01-28 14:36 ` Theodore Ts'o
2013-01-28 15:02 ` Dmitry Monakhov
2013-01-28 15:38 ` Theodore Ts'o
2013-01-29 7:41 ` Dmitry Monakhov
2013-01-29 8:37 ` Zheng Liu
2013-01-31 7:47 ` Dmitry Monakhov
2013-01-31 12:39 ` Jan Kara
2013-01-31 14:09 ` Dmitry Monakhov
2013-01-31 16:54 ` Theodore Ts'o
2013-02-09 17:10 ` REGRESSION: " Theodore Ts'o
2013-02-12 21:58 ` Jan Kara
2013-02-13 4:57 ` Theodore Ts'o
2013-02-13 7:26 ` Dmitry Monakhov
2013-02-13 15:08 ` Merge window planning for ext4 and Ted's vacation Theodore Ts'o
2013-02-14 10:47 ` REGRESSION: [PATCH 04/12] ext4: Disable merging of uninitialized extents Jan Kara
2013-02-14 16:11 ` Jan Kara
2013-02-14 19:05 ` Theodore Ts'o
2013-02-14 21:32 ` Jan Kara
2013-01-18 12:00 ` [PATCH 05/12] ext4: Remove unnecessary wait for extent conversion in ext4_fallocate() Jan Kara
2013-01-18 12:00 ` [PATCH 06/12] ext4: Move work from io_end to inode Jan Kara
2013-01-28 14:45 ` Theodore Ts'o
2013-01-18 12:00 ` [PATCH 07/12] ext4: Simplify list handling in ext4_do_flush_completed_IO() Jan Kara
2013-01-28 14:51 ` Theodore Ts'o
2013-01-18 12:00 ` [PATCH 08/12] ext4: Remove __ext4_journalled_writepage() from mpage_da_submit_io() Jan Kara
2013-01-28 14:40 ` Theodore Ts'o
2013-01-18 12:00 ` [PATCH 09/12] ext4: Dirty page has always buffers attached Jan Kara
2013-01-28 17:55 ` Theodore Ts'o
2013-01-18 12:00 ` [PATCH 10/12] ext4: Simplify mpage_add_bh_to_extent() Jan Kara
2013-01-28 18:06 ` Theodore Ts'o
2013-01-18 12:00 ` [PATCH 11/12] ext4: Make ext4_bio_writepage() handle unprepared buffers Jan Kara
2013-01-29 1:59 ` Theodore Ts'o
2013-01-18 12:00 ` [PATCH 12/12] ext4: Fix ext4_writepage() to achieve data=ordered guarantees Jan Kara
2013-01-29 2:08 ` Theodore Ts'o
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