From: Jan Kara <jack@suse.cz>
To: Kazuya Mio <k-mio@sx.jp.nec.com>
Cc: Jan Kara <jack@suse.cz>, ext4 <linux-ext4@vger.kernel.org>,
Theodore Tso <tytso@mit.edu>, Andreas Dilger <adilger@dilger.ca>
Subject: Re: [BUG] aborted ext4 leads to inifinity loop in balance_dirty_pages
Date: Wed, 2 Nov 2011 00:13:42 +0100 [thread overview]
Message-ID: <20111101231342.GJ18701@quack.suse.cz> (raw)
In-Reply-To: <4EAA3EE7.4040802@sx.jp.nec.com>
On Fri 28-10-11 14:34:31, Kazuya Mio wrote:
> 2011/10/25 22:40, Jan Kara wrote:
> > Please no. Generally this boils down to what do we do with dirty data
> >when there's error in writing them out. Currently we just throw them away
> >(e.g. in media error case) but I don't think that's a generally good thing
> >because e.g. admin may want to copy the data to other working storage or
> >so. So I think we should rather keep the data and provide a mechanism for
> >userspace to ask kernel to get rid of the data (so that we don't eventually
> >run OOM).
>
> I see. I agree with you.
>
> >>Do you have any ideas?
> > So the question is what would you like to achieve. If you just want to
> >unblock a thread then a solution would be to make a thread at
> >balance_dirty_pages() killable. If generally you want to get rid of dirty
> >memory, then I don't have a really good answer but throwing dirty data away
> >seems like a bad answer to me.
>
> The problem is that we cannot unmount the corrupted filesystem due to
> un-killable dd process. We must bring down the system to resume the service
> with no dirty pages. I think it is important for the service continuity
> to be able to kill the thread handling in balance_dirty_pages().
Sure. Then allowing a process to be killed while waiting in
balance_dirty_pages() would solve your problem. That can be done relatively
easily. I can write the patch, just now the code is under rewrite from
IO-less dirty throttling patches so I'll wait for a while for it to settle
down.
Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR
next prev parent reply other threads:[~2011-11-01 23:13 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-25 12:04 [BUG] aborted ext4 leads to inifinity loop in balance_dirty_pages Kazuya Mio
2011-10-25 13:40 ` Jan Kara
2011-10-28 5:34 ` Kazuya Mio
2011-11-01 23:13 ` Jan Kara [this message]
2011-11-02 5:24 ` Kazuya Mio
2011-11-07 8:00 ` Dmitry Monakhov
2011-11-07 17:29 ` Jan Kara
2011-11-07 17:45 ` Dmitry Monakhov
2011-11-07 21:23 ` Jan Kara
2011-11-08 0:03 ` Jan Kara
2011-11-09 8:28 ` Kazuya Mio
2011-11-09 11:15 ` Jan Kara
2011-11-14 10:06 ` Kazuya Mio
2011-11-14 11:11 ` Jan Kara
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