Old ATA disk names emulation [Was: Switch from legacy ata(4) to CAM-based ATA]

[Alexander Motin]

Arnaud Lacombe wrote:
> Hi,
> 
> 2011/4/25 Alexander Motin <mav at freebsd.org>:
>> Kostik Belousov wrote:
>>> On Mon, Apr 25, 2011 at 03:26:02PM +0300, Alexander Motin wrote:
>>>> Andrey V. Elsukov wrote:
>>>>> On 25.04.2011 14:23, Alexander Motin wrote:
>>>>>> What will not work:
>>>>>>  - old device names won't be seen inside GEOM, so users who hardcoded
>>>>>> provider names in gmirror/gstripe/... metadata (not the default
>>>>>> behavior) are still in trouble.
>>>>>>  - patch mimics ATA_STATIC_ID behavior, if user had custom kernel
>>>>>> without it, he should update device names manually.
>>>>>>  - it won't work for users with hot-unplugging ATA controllers (not
>>>>>> devices), but I believe it is really rare case.
>>>>>>  - low-level tools, such as smartmontools, won't be able to work with
>>>>>> alias devices, as background ada driver doesn't implements legacy
>>>>>> ioctls. May be I could partially fix this.
>>>>>>
>>>>>> Except those, I think this patch should work for the most of users.
>>>>>>
>>>>>> Any more objections/ideas? Is this an acceptable solution?
>>>>> what about new GEOM class? You can create new class instance after
>>>>> disk_alloc(), attach it to the new disk and create provider with old-style
>>>>> name. It seems this class will be very simple.
>>>> It sounds like less dirty option. I'll try it. Thank you. Won't
>>>> re-providing exactly the same device into GEOM create some problems?
>>>> glabel and co will connect to each of them (original and legacy) and
>>>> report two equal sets of labels.
>> I have implemented it by adding one more specialized glabel submodule:
>> http://people.freebsd.org/~mav/legacy_aliases_geom.patch
>>
> so far, so good, with that patches on 2 different machine with
> different ATA mapping (one was detected as ad0, the other ad6). I only
> tested the first patch on a single machine (was ad0), worked too.

Thank you! First patch went to HEAD.

-- 
Alexander Motin