UBIFS volume corruption (bad node at LEB 0:0)

[David Bergeron]

On 2009-01-08, at 1:46, Artem Bityutskiy wrote:
> On Wed, 2009-01-07 at 23:13 -0500, David Bergeron wrote:
>> # mount -o remount,rw,sync /
>> # rsync -aHxvi --delete ... /
>> # mount -o remount,ro /
>> # reboot -d -f
>>
>> When rebooting, the kernel fails to mount the rootfs with the
>> following error:
>>
>> [   61.033142] UBIFS error (pid 1): ubifs_read_node: bad node type  
>> (11
>> but expected 6)
>> [   61.040965] UBIFS error (pid 1): ubifs_read_node: bad node at  
>> LEB 0:0
>
> Hmm, OK. I'll try to look at this and figure out what is going wrong.
> What would help a lot is if I was able to reproduce this at my  
> setup. So
> you may help by sending a shell script which reproduces this issue, if
> you can. And it is better to work with nandsim, because this is the  
> tool
> I use here

Hi Artem,

So I am able to reproduce it on nandsim, with the following setup, it  
takes on average ~30 cycles of rsync & remount before it breaks, which  
is much more resilient than with my real setup.

Couple of observations:
- It is the read-only mount followed by a 'remount,rw' that is the  
problem enabler, nothing bad happens without doing that.
- I first tried to play with extracting tarballs but it ran fine for  
hours, when I went back to rsync'ing files it broke almost immediately.
- rsync hops between syncing two rootfs userlands, mostly identical  
besides a bunch of mtime differences and one having more files (55% vs  
88% used capacity), so far it always breaks after rsync has grown the  
data footprint, shrinking seems to go well.

I will keep poking around this issue, let me know if you want me to  
try anything.

The setup:

64MiB, 2048 bytes page
nandsim.first_id_byte=0x20 nandsim.second_id_byte=0xa2  
nandsim.third_id_byte=0x00 nandsim.fourth_id_byte=0x15

ubiformat /dev/mtd0 -s 512 -y
ubiattach /dev/ubi_ctrl -m 0
ubimkvol /dev/ubi0 -N rootfs -s 40MiB

mounted once rw to init empty filesystem then I run this:

#!/bin/sh -x

UBIFS=ubi0:rootfs
MNT=/mnt
step=1
count=0

while true; do
mount -t ubifs -o ro $UBIFS $MNT || { echo GAME OVER score $count;  
break; }
mount -o remount,rw,sync $MNT

case $step in
   1)
     rsync -aHx --delete host::systemA $MNT
     step=2 ;;
   2)
     rsync -aHx --delete host::systemB $MNT
     step=1 ;;
esac

umount $MNT
count=$((count+1))
done
-EOF-

Regards,
-david