JFFS2 Corruption.

simon at baydel.com simon at baydel.com
Mon Feb 23 06:07:59 EST 2004

As I have been trying to use this as a root filesystem I checked made checks into the 
dismounting of the filesystem. It seems that the halt script remounts root read only. 
However I found that this does not cause mtdblock to flush it's cache. I have written a 
small program to perform an ioctl BLKFLSBUF and I call it after the system mounts 
root read only. This seems to help but it is not the whole story.

I have also trawled the archives. There are some articles which list similar problems. 
It is proposed that these are related to unaligned  memory access. Can anyone 
explain why this matters and how to prevent it.

My current architecture is PPC.

Many Thanks


On 19 Feb 2004 at 16:48, simon at baydel.com wrote:

> I am having problems using JFFS2 filesystems on a NAND device. I have
> had these problems in the past an decided not to use this method for
> storing my data. I would really like to do this and I was wondering if
> anyone else had been able to run such a system reliably ? The NAND
> device is a 128MB SMC and I have downloaded the mtd code from CVS
> within the last week.
> I am using mtdpart to provide partitions but for the moment I am only
> using mtd1 as a root file system. To build this I perform the
> following steps.
> 1. Boot system via network and mount nfs root
> 2. eraseall /dev/mtd1
> 3. mount -t jffs2 /dev/mtdblock1 /smc
> 4. cd /smc
> 5. tar xvzf /rootfilesystem.tgz
> 6. unmount /smc
> I then reboot using the SMC as my root filesystem. As the system gets
> rebooted and incurrs more writes I get the following kinds of message
> Empty flash at 0x00469ffcb ends at 0x0046a000
> or
> jffs2_scan_dirent_node(): Node CRC failed on node at 0x0046a7f0 
> read 0xffffffff calculated 0xdec8161b
> I have written in before about these messages and I understand that
> the first is of no concern but the second relates to write data which
> may not have been written to the SMC.
> The thing is I have had this happen on two completely different
> harware designs. On an X86 board and the other a PPC. 
> I have checked and the OS umounts root as it shuts down. Also I cannot
> find fsck.jffs2 in the util directory. Does it exist ?
> In trying to debug this I noticed that the device was still reporting
> busy when nand_command was entered. I have put a line of code in to
> delay until the device is ready at the start of the routine. It is my
> understanding that if the device is busy when you try and
> select/deselect or send a command the outcome cannot be predicted. If
> this is not the case I would like to understand why. If it is how does
> any of the NAND code work ? 
> Any help greatly appreciated 
> Cheers Simon.
>    __________________________
> Simon Haynes - Baydel 
> Phone : 44 (0) 1372 378811
> Email : simon at baydel.com
> __________________________
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Simon Haynes - Baydel 
Phone : 44 (0) 1372 378811
Email : simon at baydel.com

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