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SubjectRe: Partitions: Amiga RDB partition on 2 TB disk way too big, while OK in AmigaOS 4.1
Date
Am Sonntag, 17. Juni 2012 schrieb Martin Steigerwald:
> Hi Jens, hi Linux m68k developers,
>
> I reported that as
>
> https://bugzilla.kernel.org/show_bug.cgi?id=43511
>
> I will attach there some more debug data like binary copy of RDB and
> such.
>
> But maybe its easier to discuss here.

I think this one is pretty serious:

merkaba:~> pvdisplay /dev/sdb1
--- Physical volume ---
PV Name /dev/sdb1
VG Name steigerwald
PV Size 1,82 TiB / not usable 4,08 MiB
Allocatable yes
PE Size 4,00 MiB
Total PE 476931
Free PE 105731
Allocated PE 371200
PV UUID ZXMECC-JAir-lX8Q-rLhS-W1cS-quwz-b3FXWp

merkaba:~> vgdisplay steigerwald
--- Volume group ---
VG Name steigerwald
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 7
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 5
Open LV 1
Max PV 0
Cur PV 1
Act PV 1
VG Size 1,82 TiB
PE Size 4,00 MiB
Total PE 476931
Alloc PE / Size 371200 / 1,42 TiB
Free PE / Size 105731 / 413,01 GiB
VG UUID uhjjE1-0yrD-Ch1A-d9qL-P5jY-UDXE-io4bpi


with

merkaba:~#1> amiga-fdisk -l /dev/sdc
Disk /dev/sdc: 3 heads, 16 sectors, 81396441 cylinders, RDB: 0
Logical Cylinders from 43 to 81396440, 24576 bytes/Cylinder

Device Boot Mount Begin End Size Pri BBlks System
/dev/sdc1 * 43 65536043 1572864024 0 0 Linux native
/dev/sdc2 * 65536044 78643244 314572824 0 0 [unknown]
/dev/sdc3 * 78643245 81396440 66076704 0 0 Amiga FFS Int.


Due to truncating oversized partition instead of refusing to use
them the PV and consequently VG span the whole disk instead
of leaving space for the >350GB in the two other partitions:

merkaba:~> cat /proc/partitions
major minor #blocks name

[…]
8 16 1953514584 sdb
8 17 1953513552 sdb1

(now sdb instead of sdc back when I run amiga-fdisk)


This is just asking for trouble. Thus:

Bug 43521 - Amiga RDB partitions: truncates miscaluted partitions size instead of refusing to use it
https://bugzilla.kernel.org/show_bug.cgi?id=43521


My suggestion is to bail out if a partition size looks insane and impossible.
Having to manually fix it up to access the data on disk still looks better
to me than potentially overwriting lots of data.



Until today I never actually did an Amiga backup to the disk, I just
created the two Amiga partitions and copied some screenshots of them
but that might be enough to explain the checksum errors I found in a
BTRFS backup partition.

I am now checking my Linux backups. They might be save, cause not all
space on the volume group is used.

See:

kernel got struck while scrubbing BTRFS with node- and leafsize 32768
http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg17108.html

s/struck/stuck

Thanks,
--
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7
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