linux-kernel - Re: Power plug off / on - EXT4-fs (sda1): re-mounted. Opts: errors=remount-ro,commit=600

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Message-ID: <4D2F5EFE.6060407@windriver.com>
Date:	Thu, 13 Jan 2011 14:22:22 -0600
From:	Jason Wessel <jason.wessel@...driver.com>
To:	Theodore Tso <tytso@....edu>
CC:	"Luis R. Rodriguez" <mcgrof@...il.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Power plug off / on - EXT4-fs (sda1): re-mounted. Opts: errors=remount-ro,commit=600

On 01/12/2011 06:09 PM, Theodore Tso wrote:
> 
> On Jan 12, 2011, at 4:35 PM, Luis R. Rodriguez wrote:
> 
>> When I yank my power chord off of my Thinkpad T61 running 2.6.37 I get
>> the following:
>>
>> [   79.523778] Monitor-Mwait will be used to enter C-3 state
>> [   81.195402] EXT4-fs (sda1): re-mounted. Opts: errors=remount-ro,commit=600
>>
>> mcgrof@tux ~ $ mount| grep sda1
>> /dev/sda1 on / type ext4 (rw,errors=remount-ro,commit=600)
> 
> Sounds like you have some userspace script which is being triggered on the transition running on batteries, and it's doing a remount -o commit=600 to save power.   Are you using laptop_mode by any chance?
> 

That is interesting indeed.   While I am running a substantially older kernel ( 2.6.35-24-generic #42-Ubuntu 10.10 ).  I was seeing a consistent problem where if you pulled the power cord while the system was under heavy I/O load, you could no longer run sync.  The jbd2 process just kept on running forever continuously.  Shutdown was impossible to because vfs unmount blocked (hold power key for 4+ seconds...).

The script in question is: 

/usr/lib/pm-utils/power.d/journal-commit

I commented out the line: 

#       mount -o remount,$2 $1

And now gone is the nasty problem of not being able to shutdown or have processes block on a call to sync().  Clearly this is nothing more than a band aid, and perhaps it is fixed in a newer kernel (one can hope anyway).

Cheers,
Jason.
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