ubifs_decompress: cannot decompress ...

[Artem Bityutskiy]

On Wed, 2011-06-08 at 13:50 -0400, Matthew L. Creech wrote:
> On Wed, Jun 8, 2011 at 10:11 AM, Artem Bityutskiy <dedekind1 at gmail.com> wrote:
> >
> > Yes, it does look like this LEB might be garbage-collected. But it does
> > not have to be.
> >
> > Anyway, what I can suggest you is to do several things.
> >
> > 1. If you have many occasions of such error, try to gather some
> >   information about how the device was used, and if it was uncleanly
> >   power-cut. Remember, I often saw that embedded devices have incorrect
> >   reboot. Whe users reboot it "normally" - it does not try to unmount
> >   the FS-es cleanly and just jumps to som HW reset function.
> >
> >   You can verify this by rebooting normally and checking if UBIFS says
> >   "recovery needed" or not. If it does - the reboot was not normal.
> >
> 
> Yes, it currently reboots uncleanly (though it does do a "sync"
> first).  I noticed this a while back, and the next release firmware
> will have it fixed.  However, it doesn't make a huge difference to us,
> because these devices are probably more likely to experience power
> loss than a software reboot, in the field at least.
> 
> > 2. This error may be due to memory corruptions in some driver (e.g.,
> >   wireless or video), due to issues in the mtd driver, etc. Try to
> >   stress your system with slub/slab full checks enabled, and other
> >   debugging features which you can find in the "hacking" section of
> >   make menuconfig.
> >
> 
> Will do.
> 
> > 3. If my theory is true, then what may help is adding a check it
> >   ubifs recovery function. The recovery ends with an ubifs_leb_change()
> >   call. You need to check the last node there - is it full and correct?
> >   If not, you should print a loud warning and information like leb dump
> >   _before_ the change, and dump of the buffer which we are going to
> >   write with ubifs_leb_change().
> >
> >   You'd probably need to deploy this check to the field if this issue
> >   is not easy to reproduce. If you have then this info you may fix the
> >   bug.
> >
> 
> Great, I'll add this check and see if we get any hits.  Even if it
> takes a while to hit it in the field, this would at least give us a
> way to make some progress in finding the issue.

With my latest code-base, I am able to inject a hack into
ubifs_leb_change() - but this function does not exist in your code-base.
Anyway, I'm currently running power cut emulation testing with the
following hack: