On 13/04/11 22:42, Charles Manning wrote:
> On Wednesday 13 April 2011 22:48:18 Nick Thompson wrote:
>> yaffs [master] snapshot from today, linux 2.6.33-rc4
>>
>> I have patched my kernel with yaffs for testing.
>>
>> I did:
>>
>> flash_eraseall /dev/mtd3
>> mount -t yaffs /dev/mtdblock3 /mnt/nand
>> cd /mnt/nand
>> touch test
>> cd ..
>> umount nand
>> mount -t yaffs /dev/mtdblock3 /mnt/nand
>> cd nand
>>
>> ls showed no files (except for lost+found). I turned on logging of erase
>> blocks (YAFFS_TRACE_ERASE) and dmesg showed the following:
>>
>> yaffs: dev is 32505859 name is "mtdblock3" rw
>> yaffs: passed flags ""
>> yaffs: yaffs: Attempting MTD mount of 31.3,"mtdblock3"
>> yaffs: auto selecting yaffs2
>> yaffs: block 2255 is bad
>> yaffs: block 2572 is bad
>> yaffs: block 2574 is bad
>> yaffs: block 3387 is bad
>> yaffs: block 3843 is bad
>> yaffs: block 3845 is bad
>> yaffs: block 4033 is bad
>> yaffs: yaffs_read_super: is_checkpointed 0
>> yaffs: dev is 32505859 name is "mtdblock3" rw
>> yaffs: passed flags ""
>> yaffs: yaffs: Attempting MTD mount of 31.3,"mtdblock3"
>> yaffs: auto selecting yaffs2
>> yaffs: block 2255 is bad
>> yaffs: block 2572 is bad
>> yaffs: block 2574 is bad
>> yaffs: block 3387 is bad
>> yaffs: block 3843 is bad
>> yaffs: block 3845 is bad
>> yaffs: block 4033 is bad
>> yaffs: yaffs_read_super: is_checkpointed 0
>> yaffs: yaffs_block_became_dirty block 1 state 8
>> yaffs: Erased block 1
>>
>> Obviously it didn't like the fist block, which I assumed had my file in
>> it, and decided to erase it.
> 
> This is almost certainly due to your flash driver mangling the tags stored in 
> oob.
> 
>>
>> What else should I log to try and figure out what is going on?
> 
> Turn on some of the MTD level and verification tracing in yaffs.
> 
> You might also want to add some printks to the flash driver.
>> jffs2 on 
>> the same partition passes this same test, so I believe the NAND is work
>> okay.
> 
> JFFS2 does not use oob so makes different use of the flash driver. It is 
> possible for one fs to work and another not if a driver is broken.
> 
> -- Charles

Thanks Charles, that is useful input.

I sprinkled printks around like confetti and couldn't find anything really
wrong, but I did notice the yaffs tracing showing eccres of 3 in many
places.

This prompted me to check the NAND driver again, but in the end it seems
this is due to yaffs_UnpackTags2 running its own ECC checks, which detects
errors that it can't fix.

I tuned checking off by default (CONFIG_YAFFS_DISABLE_TAGS_ECC=y) and things
look better now.

Is this because the number of free bytes in my OOB is not enough? I have
22 free bytes starting as offset 2. I guess that the tag data fits, but
the ECC doesn't. sizeof(yaffs_PackedTags2TagsPart) + sizeof(yaffs_ECCOther)
is 28 bytes I think.

Maybe I'm wrong about that and it's simply not being written correctly -
though that would seem odd as I assume the tag data itself is okay...

Is it safe to turn off the extra ECC? I assume without it the tag data is
not protected in any way. That doesn't sound very safe.

Thanks,
Nick.