Re: UBI/UBFS: ubi_eba_read_leb() reporting unmapped LEB

[Steve B <steve@baconbits.demon.co.uk>]

The log on the target is very minimal as I was only capturing error
logs, so don't have much info to share on that, but here is the log from
the target:

[   13.178297] UBIFS error (pid 1273): ubifs_read_node: bad node type (255 but expected 1)
[   13.178481] UBIFS error (pid 1273): ubifs_read_node: bad node at LEB 39:0, LEB mapping status 0
[   13.178668] Not a node, first 24 bytes:
[   13.178755] 00000000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff                          ........................
[   13.179093] [<80012b7c>] (unwind_backtrace+0x0/0x11c) from [<80131138>] (ubifs_read_node+0x25c/0x2a0)
[   13.179311] [<80131138>] (ubifs_read_node+0x25c/0x2a0) from [<8014d2ac>] (ubifs_tnc_read_node+0x60/0x198)
[   13.185906] [<8014d2ac>] (ubifs_tnc_read_node+0x60/0x198) from [<801343e0>] (ubifs_tnc_locate+0xa8/0x180)
[   13.195449] [<801343e0>] (ubifs_tnc_locate+0xa8/0x180) from [<80126e1c>] (do_readpage+0x1bc/0x448)
[   13.204388] [<80126e1c>] (do_readpage+0x1bc/0x448) from [<801284f8>] (ubifs_readpage+0x3e8/0x428)
[   13.213246] [<801284f8>] (ubifs_readpage+0x3e8/0x428) from [<8008e6e4>] (generic_file_aio_read+0x328/0x6f4)
[   13.222973] [<8008e6e4>] (generic_file_aio_read+0x328/0x6f4) from [<800b37c4>] (do_sync_read+0x98/0xd4)
[   13.232342] [<800b37c4>] (do_sync_read+0x98/0xd4) from [<800b3e0c>] (vfs_read+0xa4/0x134)
[   13.240501] [<800b3e0c>] (vfs_read+0xa4/0x134) from [<800b4190>] (sys_read+0x34/0x68)
[   13.248316] [<800b4190>] (sys_read+0x34/0x68) from [<8000e280>] (ret_fast_syscall+0x0/0x30)
[   13.256639] UBIFS error (pid 1273): do_readpage: cannot read page 991 of inode 91, error -22
[   13.265085] UBIFS error (pid 1273): ubifs_read_node: bad node type (255 but expected 1)
[   13.273046] UBIFS error (pid 1273): ubifs_read_node: bad node at LEB 39:0, LEB mapping status 0

I'm currently trying to create a test to more reliably reproduce the issue,
when I do I can share those logs.

Fastmap doesn't exist in the kernel version we are running (3.4.0)

The first test to show up this issue simple copies a file in a tight loop and
power is pulled randomly on the board. I am now trying to refine the test to speed
up the failure by randomly pulling the power in the NAND driver after a random 
number of erase/write calls, but I haven't been able to reproduce the issue
with this.

I'm fairly sure the reconstructed image is correct as it's producing the same 
backtrace as the original issue on the target. My program that scans the NAND 
flash dump for UBI headers confirms that the expected mapping is missing.



On Mon, 20 Oct 2014, Artem Bityutskiy wrote:

> On Mon, 2014-10-20 at 14:48 +0100, Steve B wrote:
>> Hi Artem,
>>
>> Thanks for the reply.
>>
>> I have the kernel built with:
>> CONFIG_MTD_UBI_DEBUG=y
>> CONFIG_UBIFS_FS=y
>>
>> The failure was seen on an embedded device, I dumped the flash
>> contents (raw format) and then re-constructed the image on my Linux PC
>> using nandsim with UBI and UBIFS modules i've built with some extra debugging.
>> The call stack in the log posted is the same as the one seen on the device
>> that showed the original problem.
>>
>
> I see. Would you post the full log, not just the extract near the
> failure message?
>
>> From what I see so far, UBIFS believes that the data of a file is stored
> in LEB 352. But UBI says: "nope, this LEB was unmapped".
>
> So the bug may be in both UBIFS and UBI.
>
> When we were writing this code years ago, we were stressing UBIFS
> power-cut tolerance a lot. We dead real power cuts, but we did emulated
> power cuts a lot more than real. And emulated power cuts only test
> UBIFS, not UBI. On the other hand, UBI is very simple comparing to
> UBIFS.
>
> BTW, do you have fastmap enabled or disabled?
>
> Are you doing deliberate power cut testing, or you hit this error by
> chance? In the former case, you may enable additional debugging,
> probably, depending on how many test-boxes are you stressing
> simultaneously.
>
> Also, are you 100% sure you "reconstructed" the image correctly, and you
> are not wasting time looking at irrelevant errors?
>
> Artem.
>
>
>