Random Kernel Panic on Dreamplug (FS related)

[Ian Lepore]

On Sun, 2014-09-28 at 21:01 -0700, John-Mark Gurney wrote:
> Mattia Rossi wrote this message on Fri, Sep 26, 2014 at 14:19 +0200:
> > This might be part of the weird FFS issues the Dreamplug has and no-one 
> > knows why they're happening.
> 
> Are you running w/ FFS journaling?  If so, try turning it off, but
> keeping softupdates on..
> 

It's not an SU+J problem, or even an SU problem.  fsck finds
non-existant errors on filesystems known to be clean, and if
write-enabled it will corrupt the good filesystem when attempting to
correct those "errors".  This is on armv4 only, not v6.  I tested with
and without softupdates on.  I tested with UFS1 and UFS2 filesystems.
You can even do a newfs followed immediately by an fsck on it and it
will corrupt the fs.

The one thing I haven't done is opened a PR for this.

> > data_abort_handler() at data_abort_handler+0x5c0
> >          pc = 0xc0de7a28  lr = 0xc0dd711c (exception_exit)
> >          sp = 0xde019898  fp = 0xde019a20
> >          r4 = 0xffffffff  r5 = 0xffff1004
> >          r6 = 0xc3f3f6c0  r7 = 0x00001000
> >          r8 = 0xc443e880  r9 = 0x00000000
> >         r10 = 0xc3d69000
> > exception_exit() at exception_exit
> >          pc = 0xc0dd711c  lr = 0xc0d53828 (ffs_truncate+0xaa8)
> >          sp = 0xde0198e8  fp = 0xde019a20
> >          r0 = 0xd0238120  r1 = 0x00000e60
> >          r2 = 0x00000000  r3 = 0x00000000
> >          r4 = 0x00000120  r5 = 0x00000000
> >          r6 = 0xc3f3f6c0  r7 = 0x00001000
> >          r8 = 0xc443e880  r9 = 0x00000000
> >         r10 = 0xc3d69000 r12 = 0xd0238120
> > memset() at memset+0x48
> >          pc = 0xc0de521c  lr = 0xc0d53828 (ffs_truncate+0xaa8)
> >          sp = 0xde0198e8  fp = 0xde019a20
> > Unwind failure (no registers changed)
> 
> No more beyond this?   If you could run addr2line on 0xc0d53828 so
> that we know where in ffs_truncate it's failing, that'd be very
> nice...
> 

Some time in the past 4-6 weeks something has gone wrong with kernel
stack backtraces.  Sometimes you get a full useful traceback, and more
often it ends at the function that triggered the exception, always with
a "no registers changed" message.

-- Ian

> > The sad thing is, that with fsck broken for the dreamplug, I have to 
> > re-format the disk, reinstall everything and recreate the config files 
> > which I didn't manage to copy to a safe place beforehand :-(
> > 
> > Before I do that I'll leave the system in debugging mode for a few days, 
> > in case someone can help and needs some more information.
> > 
> > Cheers,
> > 
> > Mat