Re: Top 10 kernel oopses for the week ending January 5th, 2008

Neil Brown
2008-01-14T01:36:38Z

On Thursday January 10, viro@ZenIV.linux.org.uk wrote:
> On Thu, Jan 10, 2008 at 03:13:48PM +1100, Neil Brown wrote:
> > > What guarantees that it doesn't happen before we get to callback? AFAICS,
> > > nothing whatsoever...
> >
> > Yes, that's bad isn't it :-)
> >
> > I think I should be using sysfs_schedule_callback here. That makes the
> > required 'get' and 'put' calls.... but it can fail with -ENOMEM. I
> > wonder what I do if -ENOMEM??? Maybe I'll just continue to roll my
> > one :-(
>
> How about this instead (completely untested)
>
> * split failure exits
> * switch to kick_rdev_from_array()
> * fold unbind_rdev_from_array() into it (no other callers anymore)
> * take export_rdev() into failure case in bind_rdev_to_array()
> * in kick_rdev_from_array() do what export_rdev() does sans
> kobject_put() and do that before schedule_work(). Take kobject_put() into
> delayed_delete().

While there are probably some good ideas in there, I think fixing this
particular bug is much simpler. Just take a reference to the object
before scheduling the worker, and drop it when the worker has done
its work.

I have a closer look at the idea of no required export_rdev after a
failed bind_rdev_to_array. On the surface it does seem to make the
code nicer.

Thanks,
NeilBrown