bug#80093: libparted: gpt: Partition type is not updated after changing file system

On 23/03/2026 at 19:49, Brian C. Lane wrote:
>>
>> In a GPT partition table, when the file system type of a partition is set to
>> a Microsoft filesystem (ex: FAT) with ped_partition_set_system(),
>> gpt_partition_set_system() sets the partition type to
>> PARTITION_BASIC_DATA_GUID (Microsoft basic data partition type GUID),
>> resulting in the "msftdata" flag being set. As expected.
>>
>> However when a partition has the PARTITION_BASIC_DATA_GUID type, if the
>> filesystem type is changed to a non-Microsoft filesystem (ex: ext4),
>> gpt_partition_set_system() does not reset the partition type to the
>> associated partition type GUID (ex: PARTITION_LINUX_DATA_GUID), resulting in
>> the "msftdata" flag still being set.
>>
>> It is the same with the PARTITION_SWAP_GUID partition type.
>>
>> This is caused by PARTITION_BASIC_DATA_GUID and PARTITION_SWAP_GUID being
>> included in skip_set_system_guids[]. Is there a reason for this or is it a
>> bug ? Shouldn't all filesystem-specific partition types be excluded from
>> this list ?
> 
> This isn't a bug. The partition GUID is only set at creation time, using
> input from the user to pick the most appropriate type. But parted isn't
> (and should not be) tracking filesystem changes and changing the GUID.

This does not match my observations:
- ped_partition_set_system() can set the 'msftdata' or 'swap' flag on an 
existing partition, it just cannot clear it.
- ped_partition_set_flag() sets the 'msftdata' or 'swap' flag in 
accordance with the detected filesystem when clearing the GUID type flag 
(esp, raid...) on an existing partition. Easy to reproduce with parted.