From: Zheng Liu <gnehzuil.liu@gmail.com>
To: Dmitry Monakhov <dmonakhov@openvz.org>
Cc: linux-ext4@vger.kernel.org, tytso@mit.edu, jack@suse.cz,
wenqing.lz@taobao.com
Subject: Re: [PATCH 4/7] ext4: fsync should wait for DIO writers
Date: Thu, 13 Sep 2012 20:36:32 +0800 [thread overview]
Message-ID: <20120913123632.GA13319@gmail.com> (raw)
In-Reply-To: <874nn25gqi.fsf@openvz.org>
On Thu, Sep 13, 2012 at 03:01:25PM +0400, Dmitry Monakhov wrote:
> On Thu, 13 Sep 2012 18:46:21 +0800, Zheng Liu <gnehzuil.liu@gmail.com> wrote:
> > On Sun, Sep 09, 2012 at 09:27:11PM +0400, Dmitry Monakhov wrote:
> > > fsync and punch_hole are the places where we have to wait for all
> > > existing writers (writeback, aio, dio), but currently we simply
> > > flush pended end_io request which is not sufficient.
> > > Even more i_mutex is not holded while punch_hole which obviously
> > > result in dangerous data corruption due to write-after-free.
> >
> > Hi Dmitry,
> >
> > Lukas already has a patch to take i_mutex locking before punching a
> > hole. Just a reminding. :-)
> Yes, i've found it after patch was submitted, but this bug make me
> nervous a bit because we have broken punch_hole implementation
> long time ago, it allow to destroy data easily, user are able to
> call it if has WR permission for a file.
> So if you ask be i'll vote for hide it under CAP_SYS_RESOURCE until
> proper implementation appears.
> Same it true for EXT4_IO_MOVE_EXT because it allow to kernel panic
> since v2.6.30-6558-g748de67, so all primary distros (RH6,Deb6) are
> affected :(
IMHO, it will be better when this patch is applied, and I prefer to fix
the problem rather than hidding it using CAP_SYS_RESOURCE. ;-)
Regards,
Zheng
next prev parent reply other threads:[~2012-09-13 12:26 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-09 17:27 [PATCH 0/7] ext4: Bunch of DIO/AIO fixes Dmitry Monakhov
2012-09-09 17:27 ` [PATCH 1/7] ext4: ext4_inode_info diet Dmitry Monakhov
2012-09-13 10:50 ` Zheng Liu
2012-09-13 11:15 ` Dmitry Monakhov
2012-09-15 15:53 ` Theodore Ts'o
2012-09-09 17:27 ` [PATCH 2/7] ext4: completed_io locking cleanup Dmitry Monakhov
2012-09-10 9:23 ` Jan Kara
2012-09-10 10:19 ` Dmitry Monakhov
2012-09-13 10:48 ` Zheng Liu
2012-09-09 17:27 ` [PATCH 3/7] ext4: serialize dio nolocked reads with defrag workers V2 Dmitry Monakhov
2012-09-10 9:31 ` Jan Kara
2012-09-10 10:00 ` Jan Kara
2012-09-09 17:27 ` [PATCH 4/7] ext4: fsync should wait for DIO writers Dmitry Monakhov
2012-09-10 9:51 ` Jan Kara
2012-09-10 10:56 ` Dmitry Monakhov
2012-09-12 14:02 ` Jan Kara
2012-09-12 5:40 ` Zheng Liu
2012-09-13 10:46 ` Zheng Liu
2012-09-13 11:01 ` Dmitry Monakhov
2012-09-13 12:36 ` Zheng Liu [this message]
2012-09-09 17:27 ` [PATCH 5/7] ext4: serialize unlocked dio reads with truncate Dmitry Monakhov
2012-09-10 9:54 ` Jan Kara
2012-09-09 17:27 ` [PATCH 6/7] ext4: endless truncate due to nonlocked dio readers V2 Dmitry Monakhov
2012-09-13 10:41 ` Zheng Liu
2012-09-13 12:07 ` Jan Kara
2012-09-13 12:57 ` Zheng Liu
2012-09-13 14:34 ` Jan Kara
2012-09-13 23:31 ` Zheng Liu
2012-09-09 17:27 ` [PATCH 7/7] ext4: serialize truncate with owerwrite DIO workers V2 Dmitry Monakhov
2012-09-13 10:37 ` Zheng Liu
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