Re: [RFC][PATCH] Devices visibility container

[ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman)]

Dave Hansen <haveblue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org> writes:

> On Tue, 2007-09-25 at 07:30 -0600, Eric W. Biederman wrote:
>> Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org> writes:
>> >
>> > Oh! Can you provide us an example when after the migration some
>> > device's major+minor pair change on the same device?
>> 
>> SCSI disks on a SAN.  Network accessible block devices.
>> All kinds of logical/virtual devices like ttys, the loop device, and
>> ramdisks.
>> 
>> It isn't especially frequent that something cares, but fundamentally
>> the same issues apply.
>
> To be clear, this just covers cases where an application has
> _internalized_ the device number, right?

Also cases where you want to call mknod in the container.

> Most applications should be pretty happy with the devices having
> persistent device names across a restart, and we can do that with udev
> and no kernel patching.

Yes.  But the applications that do internalize stat data from files
aren't that uncommon.  git, and backup software etc.

There is also a fair bit of work that is needed to get sysfs
and the hotplug events isolated, when we start allowing mknod etc.

Basically if I figure if we are going to deal with this we need to handle
the entire problem because these pieces are user visible.  I don't
think it is a great priority.

Eric