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From: Konstantin Kletschke <lists@ku-gbr.de>
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Subject: Re: jffs2 with sync burst mode
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Am 2005-03-10 16:21 +0000 schrieb Artem B. Bityuckiy:
> > 00435660: 0000 0000 0000 0000 b882 2ec7 8519 01e0  ................
> > 00435670: 3c00 0000 c001 e8b0 fb00 0000 1300 0000  <...............
>             ^
>             node length
> > 00435680: 0d01 0000 9400 0000 1408 0000 55ff 2d7c  ............U.-|
>                                 ^
>                                 name length
> > 00435690: a9c7 cf9f 6c69 6270 7468 7265 6164 2d30  ....libpthread-0
>             ^^^^ ^^^^
>             Name CRC
> > 004356a0: 2e39 2e32 362e 736f 8519 02c0 a906 0000  .9.26.so........
> > 004356b0: 4a1e 6fb8 0d01 0000 0200 0000 a481 0000  J.o.............
> > 004356c0: 0000 0000 0010 0000 9400 0000 9400 0000  ................
> Where has this dump come from?

My initial Mail:

I did "cat /dev/mtdblock3 > file1" into nfs-root (as a side note, I did
the same again with dd bs=1024k:
konsti at synertronixx3:/usr/src/debian_arm/ > md5sum ddmtdblock3 
e871d71c52d93c1cafb4a8f4ff47a741  ddmtdblock3
konsti at synertronixx3:/usr/src/debian_arm/ > md5sum mtdblock3 
e871d71c52d93c1cafb4a8f4ff47a741  mtdblock3
).

This is emacs in hexl-mode on these files:

> This dump looks good:

And this dump is read from the same system right after umounting.

> * the length of node is 0x3c
> * the length of the name is 0x14
> * the name CRC - don't know, didn't calculate.
> 
> Looks like JFFS2 really reads messed data from flash and I think this 
> isn't JFFS2'd failure.

> I'd suggest to hack the write function and after each write read the data 
> that has just been written again and check it has is the same as the 
> original data. This check might be done either on MTD layer or on JFFS2 
> layer.

But the error seems quite systematic so I suspect software. But of
course, still my setup my be broken and jffs2 triggers something. I have
no clue what though.
I will look into the code and see if I find the "write" to read
afterwards... :/

Konsti

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