Re: [PATCH parted] Handle swap flag in msdos type labels

[Jim Meyering]

Hans de Goede wrote:
> On 10/13/2009 12:07 PM, Jim Meyering wrote:
>> Hans de Goede wrote:
>>> From: David Cantrell<address@hidden>
>>>
>>> Original patch by David Cantrell<address@hidden>, I
>>> (Hans de Goede<address@hidden>) made the following changes:
>>> -msdos_partition_is_flag_available() should return 1 for swap flag
>>> -Only change the partition type to 82 when setting the swap flag
>>>   on dos labels, not when resetting it
>>
>> Hans,
>>
>> What is the motivation for this change?
>>
>> The existing "set 1 swap on" functionality is documented to be
>> specific to MAC partition tables:
>>
>>      `swap'
>>            (Mac) - this flag should be enabled if the partition is the
>>            swap device to be used by Linux.
>>
>>
>> AFAICS, it's not intended to be a general (partition-table-independent)
>> way to set the per- partition "type".  For an msdos partition table,
>> if you just want to set the type of a newly-created partition to swap(82),
>> use mkpart's file system type argument:
>>
>>      parted -s $dev mkpart primary linux-swap 60s 100s
>
> ATM anaconda is not calling ped_partition_set_system() but only
> setting the flag for swap partitions. It would seem reasonable to expect
> this to work for any label type which has a separate type for swap partitions.
>
> I must say having both flags and fstype in the first place is a bit confusing,
> other then the boot, lba and hidden flag most other flags seem to just be
> duplicating things which could / should be done by fstype so if we ever decide
> to break API we should clean this up.
>
> Also having non partition-table-independent API calls in general is a bad idea
> IMHO. Why can't the MAC label code check fstype too, or the others honour the
> swap flag too? The current behaviour seems rather confusing.
>
> As for the swap flag, if you don't want to take this patch (and probably a
> similar patch for gpt soon too), then we will fix anaconda to set the fstype,
> given the above description of the swap flag, I take it that to work correctly
> independent of the label type, we should set both the flag and the fstype ?

As you say, being able to set partition FS type via "set N swap on"
seems to have far too much overlap with mkpart's fs-type-setting
mechanism.  And that is confusing.  I'd like to avoid encouraging
or expanding the use of the "flag"-setting approach.

So how about a new interface, say "set-fs-type N TYPE" to set
the FS type of partition N to be TYPE?  TYPE would be one of
the same names that you can already use with mkpart, like
linux-swap, above.