Filesystems over UBI can't handle badblocks

Wed Feb 24 12:08:20 PST 2016

Hello,

I'm using ubiblk to run cramfs over UBI (the cramfs partition contains my rootfs), but I'm still having trouble handling bad blocks.

I'm using a 128MB NAND, with a 128 kB block size, 2048 B page size.

This is my ubinize config file:

[fs-volume]
mode=ubi
image=cramfs.img
vol_id=1
vol_size=20MiB
vol_type=dynamic
vol_name=fs
vol_flags=autoresize

And I generate the images as such:
mkfs.cramfs fs_dir cramfs.img
ubinize -o fs_on_ubi.img -m 2048 -p 128KiB -O 2048 ubinize.cfg

If I flash these into my system via u-boot, it works without a problem. The issue starts when marking a block as bad (via nand markbad): if I mark the first two blocks as bad, the system boots normally, If I mark any block from the third onwards, the system is able to mount rootfs, by fails soon after with a "Error while decompressing" message. Here is an excerpt from my boot log:

Skip to the important stuff
[    0.710820] UBI: attaching mtd3 to ubi0
[    0.714869] UBI: physical eraseblock size:   131072 bytes (128 KiB)
[    0.721614] UBI: logical eraseblock size:    126976 bytes
[    0.727339] UBI: smallest flash I/O unit:    2048
[    0.732292] UBI: VID header offset:          2048 (aligned 2048)
[    0.738641] UBI: data offset:                4096
[    0.840392] UBI: max. sequence number:       2
[    0.851883] UBI: attached mtd3 to ubi0
[    0.855933] UBI: MTD device name:            "fs"
[    0.860886] UBI: MTD device size:            25 MiB
[    0.866048] UBI: number of good PEBs:        199
[    0.870907] UBI: number of bad PEBs:         1
[    0.875604] UBI: number of corrupted PEBs:   0
[    0.880280] UBI: max. allowed volumes:       128
[    0.885139] UBI: wear-leveling threshold:    4096
[    0.890101] UBI: number of internal volumes: 1
[    0.894776] UBI: number of user volumes:     1
[    0.899462] UBI: available PEBs:             4
[    0.904137] UBI: total number of reserved PEBs: 195
[    0.909280] UBI: number of PEBs reserved for bad PEB handling: 5
[    0.915614] UBI: max/mean erase counter: 1/0
[    0.920107] UBI: image sequence number:  441007200
[    0.925159] UBI: background thread "ubi_bgt0d" started, PID 255
[    0.931418] UBIBLK starting
[    0.934360] UBIBLK: device's major: 254
[    0.938434] Got volume fs: device 0/volume 1 of size 186
[    0.945813] OMAP Watchdog Timer Rev 0x01: initial timeout 60 sec
[    0.952401] TCP cubic registered
[    0.955883] NET: Registered protocol family 17
[    0.960601] VFP support v0.3: implementor 41 architecture 3 part 30 variant c rev 3
[    0.968713] ThumbEE CPU extension supported.
[    0.974204] clock: disabling unused clocks to save power
[    0.982964] VFS: Mounted root (cramfs filesystem) readonly on device 254:1.
[    0.990693] Freeing init memory: 120K
INIT: version 2.88 booting
[    1.311990] Error -3 while decompressing!
[    1.316284] c0332084(2516)->c3e9e000(4096)
[    1.320600] Error -3 while decompressing!
[    1.324820] c0332a58(2615)->c3e9f000(4096)
... Same message from here on onwards

As you can see, UBI starts just fine, and I'm able to initialize ubiblk and at least mount the filesystem. I thought UBI was supposed to make any badblocks transparent to the upper layers... Is there a problem with that tought, or did my manual tampering (with nand markbad) got in the way of UBI's bad block management capabilities?

I also tried switching to squashfs, but I ran into a similar problem. . I decided to use cramfs over UBI because we had run into this problem before, and after some research it seemed that is was due to cramfs' inability to handle bad blocks, so I decided to give UBI a try, hoping it would solve my problem...

Regards,
--
Guilherme de Oliveira Costa
Firmware Engineer - Autotrac Comercio Telecomunicacoes
www.autotrac.com.br
guilherme.oliveira(at)autotrac.com.br
Phone: +55 61 3307 2666

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