linux-kernel - Re: [Bug 14354] Re: ext4 increased intolerance to unclean shutdown?

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Message-ID: <20091025062202.GB1391@ucw.cz>
Date:	Sun, 25 Oct 2009 07:22:02 +0100
From:	Pavel Machek <pavel@....cz>
To:	Ric Wheeler <rwheeler@...hat.com>
Cc:	Theodore Tso <tytso@....edu>,
	Parag Warudkar <parag.lkml@...il.com>,
	LKML <linux-kernel@...r.kernel.org>, linux-ext4@...r.kernel.org,
	bugzilla-daemon@...zilla.kernel.org
Subject: Re: [Bug 14354] Re: ext4 increased intolerance to unclean shutdown?

Hi!

>>> So I have been experimenting with various root file systems on my
>>> laptop running latest git. This laptop some times has problems waking
>>> up from sleep and that results in it needing a hard reset and
>>> subsequently unclean file system.
>>>      
>> A number of people have reported this, and there is some discussion
>> and some suggestions that I've made here:
>>
>> 	http://bugzilla.kernel.org/show_bug.cgi?id=14354
>>
>> It's been very frustrating because I have not been able to replicate
>> it myself; I've been very much looking for someone who is (a) willing
>> to work with me on this, and perhaps willing to risk running fsck
>> frequently, perhaps after every single unclean shutdown, and (b) who
>> can reliably reproduce this problem.  On my system, which is a T400
>> running 9.04 with the latest git kernels, I've not been able to
>> reproduce it, despite many efforts to try to reproduce it.  (i.e.,
>> suspend the machine and then pull the battery and power; pulling the
>> battery and power, "echo c>  /proc/sysrq-trigger", etc., while
>> doing "make -j4" when the system is being uncleanly shutdown)
>>    
>
> I wonder if we might have better luck if we tested using an external  
> (e-sata or USB connected) S-ATA drive.
>
> Instead of pulling the drive's data connection, most of these have an  
> external power source that could be turned off so the drive firmware  
> won't have a chance to flush the volatile write cache. Note that some  
> drives automatically write back the cache if they have power and see a  
> bus disconnect, so hot unplugging just the e-sata or usb cable does not  
> do the trick.
>
> Given the number of cheap external drives, this should be easy to test  
> at home....

Do they support barriers?

(Anyway, you may want to use some kind of VM for testing. That should
make the testing cycle shorter, easier to reprorduce *and* more repeatable.)

									Pavel

-- 
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