Re: [PATCH v3] Make initramfs honor CONFIG_DEVTMPFS_MOUNT

[Michael Ellerman <mpe@ellerman.id.au>]

Rob Landley <rob@landley.net> writes:

> On 09/14/2017 04:17 AM, Christophe LEROY wrote:
>> Le 14/09/2017 à 01:51, Rob Landley a écrit :
>>> From: Rob Landley <rob@landley.net>
>>>
>>> Make initramfs honor CONFIG_DEVTMPFS_MOUNT, and move
>>> /dev/console open after devtmpfs mount.
>>>
>>> Add workaround for Debian bug that was copied by Ubuntu.
>> 
>> Is that a bug only for Debian ? Why ?
>
> Look down, specifically this bit:
>
>>> v2 discussion:
>>> http://lkml.iu.edu/hypermail/linux/kernel/1705.2/05611.html
>
> That's some discussion of version 2 of this patch, which was merged for
> a while last dev cycle, then backed out again because it triggered the
> same bug in a number of system init scripts:
>
>   http://lkml.iu.edu/hypermail/linux/kernel/1705.2/07072.html
>   http://lkml.iu.edu/hypermail/linux/kernel/1705.3/01182.html
>   http://lkml.iu.edu/hypermail/linux/kernel/1705.3/01505.html
>   http://lkml.iu.edu/hypermail/linux/kernel/1705.3/01320.html
>
> All of whom copied the broken error "recovery" path from debian. If they
> checked whether it was already mounted, or didn't _blank_ the /dev
> directory in response to mounting the exact same filesystem over itself
> giving -EBUSY, the system would work fine. Heck, if you built a kernel
> with a static /dev in initramfs and no devtmpfs configured in, the
> script would break things exactly the same way. The breakage is that
> script takes a hammer to a perfectly functional /dev directory and then
> continues the boot with an empty /dev. That's bonkers.
>
>> Why should a Debian bug be fixed by a workaround in the mainline kernel ?
>
> That was my argument last time, and the answer was "Breaking userspace
> is bad, mmmkay." Even when userspace is doing something REALLY OBVIOUSLY
> STUPID and it is _clearly_ their fault, as long as they got there first
> they've established the status quo and it doesn't matter how silly it is.
>
> This was explicitly stated to me here:
>
>   http://lkml.iu.edu/hypermail/linux/kernel/1705.3/03292.html
>
> I.E. don't argue with me, argue with him. :)

I'm still here. And I'm still right :)

No one wants their system to stop booting because of this obscure
functionality.

Just put it behind a new config option which defaults off. No
workarounds required, no broken systems, no long email threads required.

cheers