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

[Luis R. Rodriguez]

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)

When I plug the power chord it back in I get:

[ 216.185265] EXT4-fs (sda1): re-mounted. Opts: errors=remount-ro,commit=0

mcgrof@tux ~ $ mount | grep sda1
/dev/sda1 on / type ext4 (rw,errors=remount-ro,commit=0)

Is this to be expected?

Luis
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[Dmitry Torokhov]

On Wed, Jan 12, 2011 at 01:35:29PM -0800, 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)
>
> When I plug the power chord it back in I get:
>
> [ 216.185265] EXT4-fs (sda1): re-mounted. Opts: errors=remount-ro,commit=0
>
> mcgrof@tux ~ $ mount | grep sda1
> /dev/sda1 on / type ext4 (rw,errors=remount-ro,commit=0)
>
> Is this to be expected?
>

FWIW I do not observe anything like this on Dell Latitude d630.

--
Dmitry

[Theodore Tso]

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?

-- Ted

[Jason Wessel]

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.

[Ted Ts'o]

On Thu, Jan 13, 2011 at 02:22:22PM -0600, Jason Wessel wrote:
>
> 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...).

Yeah, there were two separate bugs that have been addressed recently;
both were in the generic VFS and writeback code. One was a fix to do
more efficient forced writeouts at umount time.

The other was a fix so that if new dirty pages are continuously being
created (by having processes always writing more pages, those dastards :-),
to make sync stop by only having it write the pages that were dirty
at the time when the sync was initiated.

- Ted