Re: [PATCH 4/4] block: expose devt for GENHD_FL_HIDDEN disks

[Hannes Reinecke <hare@suse.de>]

On 12/14/18 9:56 AM, Thadeu Lima de Souza Cascardo wrote:
> On Fri, Dec 14, 2018 at 08:47:20AM +0100, Hannes Reinecke wrote:
>> On 12/13/18 4:25 PM, Thadeu Lima de Souza Cascardo wrote:
>>> On Thu, Dec 13, 2018 at 03:32:18PM +0100, Christoph Hellwig wrote:
>>>> On Thu, Dec 13, 2018 at 10:18:40AM +0100, Hannes Reinecke wrote:
>>>>> Welll ... this is not just 'lsblk', but more importantly this will force
>>>>> udev to create _block_ device nodes for the hidden devices, essentially
>>>>> 'unhide' them.
>>>>>
>>>>> Is this what we want?
>>>>> Christoph?
>>>>> I thought the entire _point_ of having hidden devices is that the are ...
>>>>> well ... hidden ...
>>>>
>>>> Yes, that is why I really don't like the last two patches.
>>>>
>>>> And I've checked back - lsblk actually works just fine at the moment.
>>>> But it turns out once we create the slave links it stops working,
>>>> which is a really good argument against the first two patches, which
>>>> would otherwise seem nice..
>>>
>>> Which is why I have sent the "paths/" patchset in the first place. Because I
>>> did some homework and read the previous discussion about this, and how lsblk
>>> failure to behave with slave links led to the revert of the slaves/holders
>>> patch by Dr. Hannes.
>>>
>> But you haven't answered my question:
>>
>> Why can't we patch 'lsblk' to provide the required information even with the
>> current sysfs layout?
>>
> 
> I think we could, but with my Ubuntu hat on, after the kernel fix for
> initramfs-tools, that is, slaves/holders links, the user will get an updated
> kernel that breaks the current lsblk on Bionic (Ubuntu 18.04). That will
> require that we backport the lsblk fix, which is not only more work, but there
> may be users who only update from -security, which is where kernel updates end
> regularly, but not this lsblk fix.
> 
> And that kernel update is a regression against that old lsblk version.
> 
Now you get me confused.
Which kernel update you are referring to?
We do _not_ provide any 'slave' link with the current upstream, so I 
somewhat fail to see which breakage you are referring to ...

Confused,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
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