Corrupt empty space

[Kent Li]

Frederic,

I'm not sure if this is the unstable bit issue, but I just resolved such issue by enhancing my Nand driver in both Uboot code and Linux code.

The main idea is:
Read a page
If ( ECC fail ) ;then
	Check the how many 0 bit there is.
	If ( 0 bit number > tolerance value) //tolerance value is depends on the ECC correctable bits.
		Print "Fail to recover by ECC"
	Else
		Force change the 0 bits to 1
	fi
fi

This idea assume that 
1. there is not ECC fail when reading a normal page.
2. sub-page is disabled.
3. only ECC fail happen when reading an empty page.

BR
Kent Li


-----Original Message-----
From: linux-mtd [mailto:linux-mtd-bounces at lists.infradead.org] On Behalf Of HOUR Fréderic
Sent: 2014年3月11日 1:35
To: linux-mtd at lists.infradead.org
Subject: Corrupt empty space

Hello,

I'm working on UBIFS ( linux 3.3, omap138 ). I need some help with a problem on a custom board (omapl138).
I have a software that runs in background and writes data in a UBIFS volume. I can not control when the power cut happens.
Sometimes, when booting my board, I got this "common" error:

UBI: background thread "ubi_bgt0d" started, PID 391
UBIFS: recovery needed
UBIFS: recovery completed
UBIFS: mounted UBI device 0, volume 0, name "log"
UBIFS: file system size:   3174400 bytes (3100 KiB, 3 MiB, 25 LEBs)
UBIFS: journal size:       1015809 bytes (992 KiB, 0 MiB, 6 LEBs)
UBIFS: media format:       w4/r0 (latest is w4/r0)
UBIFS: default compressor: none
UBIFS: reserved for root:  149934 bytes (146 KiB)
UBIFS: recovery needed
UBIFS error (pid 395): ubifs_scan: corrupt empty space at LEB 1534:125170 UBIFS error (pid 395): ubifs_scanned_corruption: corruption at LEB 1534:125170
00000000: ffffff7f ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff  ................................
00000020: ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff  ................................
[..]
UBIFS error (pid 395): ubifs_scan: LEB 1534 scanning failed

My NAND volume could not be mounted. My problem is that I want to have an access to the files stored in this UBIFS volume.

So I had some questions : 
- What are the risk of commenting out the 'goto corrupted' in the fonction ubifs_scan? (in order to mount my partition and have an access to my files)
- Is this the "unstable bits issue"? (http://www.linux-mtd.infradead.org/doc/ubifs.html#L_unstable_bits)
- What could be a proper solution to get my files?
- Is there a solution using U-Boot?

Thanks for your help.

Regards,

Frederic

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