Re: Unaligned jffs2 dnode address - tested by nandsim

Re: Unaligned jffs2 dnode address - tested by nandsim

[Michal Simek]

Hi,

Any update on this? Does someone know if jffs dnode should be aligned or not?
I have added some developers from mtd-utils.

I have also done test with the latest mtd-utils from git and there is still 
unaligned address.

Any suggestions?

Thanks,
Michal

BTW: I have fixed problem with unaligned access in the kernel but I think the 
problem is mainly in fs generation.

Michal Simek wrote:
> Hi,
> 
> I have reached one problem with jffs2 fs ecc tested by nandsim on 
> Microblaze.
> 
> I am getting the fault like this.
> # md5sum /mnt/delete.png
> uncorrectable error :
> uncorrectable error :
> uncorrectable error :
> uncorrectable error :
> uncorrectable error :
> mtd->read(0xcda bytes from 0xc044) returned ECC error
> Data CRC 3bcfd461 != calculated CRC e6038cde for node at 0000c000
> uncorrectable error :
> uncorrectable error :
> uncorrectable error :
> uncorrectable error :
> uncorrectable error :
> mtd->read(0xcda bytes from 0xc044) returned ECC error
> Data CRC 3bcfd461 != calculated CRC e6038cde for node at 0000c000
> 
> 
> The main problem is that there is one address with is not aligned which 
> caused that ecc counting uses wrong data.
> 
> I also found in nand_ecc code that there is written
> "It is assumed that the buffers are aligned." which is definitely wrong 
> for my case. I expect that it is 4B alignment.
> 
> I generated jffs2 filesystem by the following command (mkfs.jffs2 
> revision 1.60)
> mkfs.jffs2 -n -b -e 16KiB -t -d <folder> -o test.jffs2
> 
> test.jffs2 is also attached.
> 
> I use these command to mounted:
> flash_eraseall /dev/mtd0
> nandwrite -p /dev/mtd0 /var/ftp/test.jffs2
> mount -t jffs2 mtd:"NAND simulator partition 0" /mnt
> 
> After enable some jffs2 debug message I have got the log.
> 
> [JFFS2 DBG] (74) jffs2_add_tn_to_tree: insert fragment 0x00-0x1000, ver 
> 1 at 00000900
> [JFFS2 DBG] (74) jffs2_lookup_tn: root c0c37df8, offset 0
> [JFFS2 DBG] (74) jffs2_add_tn_to_tree: 'this' found 0x1000-0x2000 (data)
> [JFFS2 DBG] (74) jffs2_add_tn_to_tree: Ponder this ver 2, 0x1000-0x1000
> [JFFS2 DBG] (74) read_dnode: After adding ver 1:
> [JFFS2 DBG] (74) read_dnode: c78432c0: v 1 r 0x0-0x1000 ov 0
> [JFFS2 DBG] (74) read_dnode: c78432e0: v 2 r 0x1000-0x2000 ov 0
> [JFFS2 DBG] (74) read_dnode: c7843300: v 3 r 0x2000-0x3000 ov 0
> [JFFS2 DBG] (74) read_dnode: c7843320: v 4 r 0x3000-0x364a ov 0
> [JFFS2 DBG] (74) read_dnode: c7843340: v 5 r 0x364a-0x4000 ov 0
> [JFFS2 DBG] (74) read_dnode: c7843360: v 6 r 0x4000-0x5000 ov 0
> [JFFS2 DBG] (74) read_dnode: c7843380: v 7 r 0x5000-0x6000 ov 0
> [JFFS2 DBG] (74) read_dnode: c78433a0: v 8 r 0x6000-0x7000 ov 0
> [JFFS2 DBG] (74) read_dnode: c78433c0: v 9 r 0x7000-0x7316 ov 0
> 
> 
> You see that tn->fn->ofs which is 0x364a which is not aligned. This 
> offset is causing
> 
> I also tried to disable zlib compression which caused that map has 
> changed and it is aligned and there is no problem with ECC computing.
> mkfs.jffs2 -n -b -e 16KiB -t -d <folder> -o test-nozlib.jffs2 -x zlib
> 
> Have you ever seen this fault with alignment?
> I think that the problem is with test.jffs2 generation.
> Is there any option to setup that everything is aligned?
> Or are you aware about any workaround how to prevent this fault?
> 
> I do some testing directly on Microblaze. Generate random files and test 
> them and I haven't seen any problem when target read/write data from 
> jffs2 on nand with ecc. The problem is only with test.jffs2 generated on 
> host I see this fault.
> 
> Thanks,
> Michal
> 


-- 
Michal Simek, Ing. (M.Eng)
PetaLogix - Linux Solutions for a Reconfigurable World
w: www.petalogix.com p: +61-7-30090663,+42-0-721842854 f: +61-7-30090663

Re: Unaligned jffs2 dnode address - tested by nandsim

[Milton Miller]

Michal Simek wrote:
> Michal Simek wrote:
> >
> > Hi,
> >
> > I have reached one problem with jffs2 fs ecc tested by nandsim on
> > Microblaze.
>
> Any update on this? Does someone know if jffs dnode should be aligned or not?
> I have added some developers from mtd-utils.
> 
> I have also done test with the latest mtd-utils from git and
> there is still unaligned address.
> 
> Any suggestions?

I vaguely remember doingn some research in this area a few years ago
looking a report on linuxppc-dev about this and the kernel's unaligned
access was dependant on the device being given a mtd point function
which means the device is directly accessible in the cpus address space.

I don't remember much beyond that and don't have time to dig.  I am
just an observer with respect to linux mtd.

> 
> Thanks,
> Michal

Hope this helps your research,
milton