Re: [PATCH 1/1] add --partuuid to probe

[Andrei Borzenkov]

27.02.2017 03:37, Vladimir 'phcoder' Serbinenko пишет:
...
>>>>> This is not NT-style. NT uses partition offset. Who uses this format?
>> Are
>>>>
>>>> This is used by util-linux and Linux kernel.
>>>>
>>>>
>>>>  *      6) PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF representing
>> the
>>>>  *         unique id of a partition if the partition table provides it.
>>>>  *         The UUID may be either an EFI/GPT UUID, or refer to an MSDOS
>>>>  *         partition using the format SSSSSSSS-PP, where SSSSSSSS is a
>>>> zero-
>>>>  *         filled hex representation of the 32-bit "NT disk signature",
>>>> and PP
>>>>  *         is a zero-filled hex representation of the 1-based partition
>>>> number.
>>>>
>>>>> you sure that partition numbers are synced with user? Even in presence
>> of
>>>>> Solaris and bsd partitions.
>>>>>
>>>>
>>>> It is not clear what we should return for nested partition. I'm not sure
>>>> whether linux kernel scans nested partitions at all in which case we
>>>> probably should follow the suite and assign PARTUUID to top-level
>>>> partitions only.
>>>>
>>> Linux scans nested partitions and it uses though numeration in dev/sdaX,
>> in
>>> some cases shifting numbering of normal partitions. In those cases grub
>> and
>>> Linux numeration get out of sync
>>>
>>
>> Can you provide example?
> 
> Bsd and Solaris partitions. I remember we had problem with numbering of
> those.
> 

Linux ignores nested BSD partitions (just tested). There are no special
files created. Of course someone needs to test what happens under
*BSD/Solaris in this case.

I never liked idea of artificial partition GUIDs for MBR, but as long as
only Linux is using them and we are consistent with its usage - so be it.

>> I tried to create nested partition table, but
>> Linux will not display it (actually attempt to "blockdev --rereadpt
>> /dev/vda5" fails with "Invalid argument").
>>
>>         if (!disk_part_scan_enabled(disk) || bdev != bdev->bd_contains)
>>                 return -EINVAL;
>>
>> Where bdev->bd_contains points to containing device for partition and to
>> itself for the whole disk.
>>
>> As util-linux does not scan partition table itself, it does show these
>> nested partitions either.
>>