Re: Temporary lockup on loopback block device

[Miklos Szeredi]

> > > Arguably we just have the wrong backing-device here, and what we should do
> > > is to propagate the real backing device's pointer through up into the
> > > filesystem.  There's machinery for this which things like DM stacks use.
> > > 
> > > I wonder if the post-2.6.23 changes happened to make this problem go away.
> > 
> > The per BDI dirty stuff in 24 should make this work, I just checked and
> > loopback thingies seem to have their own BDI, so all should be well.
> 
> This is not only about loopback (I think the lockup can happen even 
> without loopback) --- the main problem is:
> 
> Why are there over-limit dirty pages that no one is writing?

Please do a sysrq-t, and cat /proc/vmstat during the hang.  Those
will show us what exactly is happening.

I've seen this type of hang many times, and I agree with Peter, that
it's probably about loopback, and is fixed in 2.6.24-rc.

Thanks,
Miklos


-
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/