Re: Missing 2 blocks on my UBI partition

[Steve deRosier <derosier@xxxxxxxxx>]

On Tue, May 26, 2020 at 8:55 AM Patrick Doyle <wpdster@xxxxxxxxx> wrote:
>
> I'm curious to learn where 2 blocks went missing from my UBI NAND
> device... can anybody help me out:
>
> # ubinfo -a
> UBI version:                    1
> Count of UBI devices:           1
> UBI control device major/minor: 10:57
> Present UBI devices:            ubi0
>
> ubi0
> Volumes count:                           8
> Logical eraseblock size:                 126976 bytes, 124.0 KiB
> Total amount of logical eraseblocks:     1024 (130023424 bytes, 124.0 MiB)
> Amount of available logical eraseblocks: 99 (12570624 bytes, 11.9 MiB)
> Maximum count of volumes                 128
> Count of bad physical eraseblocks:       0
> Count of reserved physical eraseblocks:  20
> Current maximum erase counter value:     33
> Minimum input/output unit size:          2048 bytes
> Character device major/minor:            252:0
> Present volumes:                         0, 1, 2, 3, 4, 5, 6, 7
>
> Volume ID:   0 (on ubi0)
> Type:        static
> Alignment:   1
> Size:        127 LEBs (16125952 bytes, 15.3 MiB)
> Data bytes:  16031744 bytes (15.2 MiB)
> State:       OK
> Name:        rootfs
> Character device major/minor: 252:1
> -----------------------------------
> Volume ID:   1 (on ubi0)
> Type:        dynamic
> Alignment:   1
> Size:        529 LEBs (67170304 bytes, 64.0 MiB)
> State:       OK
> Name:        persistent
> Character device major/minor: 252:2
> -----------------------------------
> Volume ID:   2 (on ubi0)
> Type:        static
> Alignment:   1
> Size:        30 LEBs (3809280 bytes, 3.6 MiB)
> Data bytes:  3746638 bytes (3.5 MiB)
> State:       OK
> Name:        kernel
> Character device major/minor: 252:3
> -----------------------------------
> Volume ID:   3 (on ubi0)
> Type:        static
> Alignment:   1
> Size:        143 LEBs (18157568 bytes, 17.3 MiB)
> Data bytes:  18145280 bytes (17.3 MiB)
> State:       OK
> Name:        old_rootfs
> Character device major/minor: 252:4
> -----------------------------------
> Volume ID:   4 (on ubi0)
> Type:        static
> Alignment:   1
> Size:        30 LEBs (3809280 bytes, 3.6 MiB)
> Data bytes:  3745994 bytes (3.5 MiB)
> State:       OK
> Name:        old_kernel
> Character device major/minor: 252:5
> -----------------------------------
> Volume ID:   5 (on ubi0)
> Type:        static
> Alignment:   1
> Size:        38 LEBs (4825088 bytes, 4.6 MiB)
> Data bytes:  4763648 bytes (4.5 MiB)
> State:       OK
> Name:        language
> Character device major/minor: 252:6
> -----------------------------------
> Volume ID:   6 (on ubi0)
> Type:        static
> Alignment:   1
> Size:        1 LEBs (126976 bytes, 124.0 KiB)
> Data bytes:  65536 bytes (64.0 KiB)
> State:       OK
> Name:        crypto
> Character device major/minor: 252:7
> -----------------------------------
> Volume ID:   7 (on ubi0)
> Type:        static
> Alignment:   1
> Size:        1 LEBs (126976 bytes, 124.0 KiB)
> Data bytes:  65536 bytes (64.0 KiB)
> State:       OK
> Name:        prev_crypto
> Character device major/minor: 252:8
>
> This shows that I have 8 UBI Volumes with sized as:
> Size:        127 LEBs (16125952 bytes, 15.3 MiB)
> Size:        529 LEBs (67170304 bytes, 64.0 MiB)
> Size:        30 LEBs (3809280 bytes, 3.6 MiB)
> Size:        143 LEBs (18157568 bytes, 17.3 MiB)
> Size:        30 LEBs (3809280 bytes, 3.6 MiB)
> Size:        38 LEBs (4825088 bytes, 4.6 MiB)
> Size:        1 LEBs (126976 bytes, 124.0 KiB)
> Size:        1 LEBs (126976 bytes, 124.0 KiB)
> Total: 899 LEBs
> There are 99 blocks free, 20 blocks reserved, and (according to the
> documentation, 4 blocks of UBI management overhead
>
> 899+99+20+4=1022
>
> But my NAND flash has 1024 blocks.  According to ubinfo, none of them
> are marked as bad.
>
> Where did the other 2 blocks go?
>
> What am I missing?
>

The last two blocks on the NAND are typically used as a Bad Block
Table by Linux.  I imagine this is likely where the last two blocks
"went". You should see a message about that in your dmesg.

- Steve

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