[Yaffs] missing files/reused objectID

Hi,



I have a problem with some files/directories ending up in lost+found
after reboot. The scenario is that linux has booted and goes into an
automatic upgrade mode where files are read from a USB key. Some files
are copied from the USB key into the yaffs2 filesystem. Some tar and
zipped archives are copied to the yaffs2 fs and then unzipped and
untarred. Some existing files are removed; some of these files don't
actually exist. There is an option to update the linux kernel and uboot.
The kernel, uboot, and fs are in different partitions on the nand flash.
After the upgrade is finished the system is shutdown and rebooted, the
fs is checkpointed in the shutdown. When trying to reboot, the system
hangs because it cannot find some of the files needed to boot. I can
boot the system if I use a ramdisk. Mounting the yaffs fs after booting
from ramdisk shows the missing files/directories in the lost+found
directory. /bin was one of the missing directories. Looking at the start
scan debug messages and looking at the data in flash I found that the
objectId for the bin directory (261), which had a seq. number of 0x1004
was being used by a file with seq. number 0x2f09. Since the file was
found first in the backwards scan, the /bin directory was not found as
it should be. This problem only seems to occur on a small percentage of
the boards that have the upgrade run on them and is very difficult to
get it to occur. A capture of the generic messages from the upgrade (no
yaffs debuggin was enabled) does not show anything wrong.



I am on linux 2.6.30. Yaffs is from May 2009. The nand flash is 4 GB
with block size 524288, page size 4096, OOB size 128. The first approx.
34 MB is used for uboot and kernel. The upgrade size is ~21 MB, with
around 500 files. The /bin directory is not written to in the upgrade.



I have loooked at some of the oob data for the various objectId 261s but
I am not familiar enough with yaffs to have found a cause. Any help
would be appreciated.



Thanks,



Mike