From: Zheng Liu <gnehzuil.liu@gmail.com>
To: Jan Kara <jack@suse.cz>
Cc: Dmitry Monakhov <dmonakhov@openvz.org>,
linux-ext4@vger.kernel.org, tytso@mit.edu, wenqing.lz@taobao.com
Subject: Re: [PATCH 4/7] ext4: fsync should wait for DIO writers
Date: Wed, 12 Sep 2012 13:40:01 +0800 [thread overview]
Message-ID: <20120912054001.GA3149@gmail.com> (raw)
In-Reply-To: <20120910095135.GF22903@quack.suse.cz>
On Mon, Sep 10, 2012 at 11:51:35AM +0200, Jan Kara wrote:
> On Sun 09-09-12 21:27:11, 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.
> Why not? I guess you mean the fact that there can be DIO in flight for
> which end_io() was not called so it is not queued in the queue? But that is
> OK - we have not yet called aio_complete() for that IO so for userspace the
> write has not happened yet. Thus there's no need to flush it to disk -
> fsync() does not say anything about writes in progress while fsync is
> called.
>
> > Even more i_mutex is not holded while punch_hole which obviously
> > result in dangerous data corruption due to write-after-free.
> Yes, that's a bug. I also noticed that but didn't get to fixing it (I'm
> actually working on a more long term fix using range locking but that's
> more of a research project so having somehow fixed at least the most
> blatant locking problems is good).
Hi Jan,
Could you please share more detailed information about range locking
with me? Actually, the goal of extent status tree is to implement a
range locking in ext4 [1], and I am working on it. So I think that
you have some good ideas to share with me. :-)
1. http://www.spinics.net/lists/linux-ext4/msg32661.html
If you have some problems, please let me know. Thanks!
Regards,
Zheng
next prev parent reply other threads:[~2012-09-12 5:29 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 [this message]
2012-09-13 10:46 ` Zheng Liu
2012-09-13 11:01 ` Dmitry Monakhov
2012-09-13 12:36 ` Zheng Liu
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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