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

[Ric Wheeler]

On 10/25/2009 02:22 AM, Pavel Machek wrote:
> 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

The drives themselves will support barriers - they are the same S-ATA/ATA drives 
you get normally for your desktop, etc.

I think that e-SATA would have no trouble (but fewer boxes have that external 
S-ATA port). Not sure how reliable the SCSI -> USB -> ATA conversion is for USB 
drives though (a lot of moving pieces there!).

VM testing is a good idea, but I worry that the virtual IO stack support for 
data integrity is still somewhat shaky. Christoph was working on fixing various 
bits and pieces I think...

ric

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/