Re: udev and devfs - The final word

viro
2004-01-05T04:38:34Z

On Sun, Jan 04, 2004 at 08:02:20PM -0800, Linus Torvalds wrote:
>
>
> On Mon, 5 Jan 2004 viro@parcelfarce.linux.theplanet.co.uk wrote:
> >
> > What is _not_ OK, though, is to have folks suddenly see /dev/hda3 changing
> > its device number - then we would break existing setups that worked all
> > along; even if admin can fix the breakage, it's not a good thing to do.
>
> Ehh, it will actually happen.
>
> If nothing else, things like SATA will end up meaning that the device you
> were used to seeign as /dev/hdc will suddenly show up as /dev/scd0
> instead. Just because you changed the cabling while you upgraded to a
> newer version of your CD-ROM drive.

If I open the damn box, I sure as hell can be bothered to edit stuff in
/etc...

> And the thing is, with fs labels and udev, even "existing systems" really
> shouldn't much care.
>
> Now, we'd probably not want to force the switch, but I do suspect we'll
> have exactly this as a switch in the "Kernel Debugging Config" section.
> Where even _common_ things like disks could end up with per-bootup values.
> Just to verify that every part of the system ends up having it right.

Then we'd better have a very good idea of the things that are going to
break. Note that right now even late-boot code in kernel itself will
break on that - there are explicit checks for ROOT_DEV==MKDEV(2,0),
all sorts of weird crap deep in the bowels of arch/ppc/*/*, etc.

It won't be an easy transition - I know that Greg is very optimistic
about it, but there will be a *lot* of crap to take care of. In theory
getting bigger dev_t should've been very straightforward, but if you
check what really had been involved...

ObOtherStraightforwardThings: net_device refcounting. Take a look at
Jeff's queue someday - by now it's one big merge short of getting it
right for practically all drivers. 1.9Mb total + 247Kb pending patches
here. Several hundreds changesets, practically all of them fixing
exploitable holes. And yes, most of them had been bugs all along -
since 2.2 if not earlier. Sure, that made things better, but if somebody
comes along and makes similar "fun" necessary for e.g. ALSA...

> because "pine" still doesn't get UTF-8 right, and nobody is apparently
> ever going to fix it. Oh, well. But at least I know I'm doing something
> _wrong_, which in itself is a good thing.).

Heh. Took you long enough - "using pine" should've been a dead giveaway
from the very beginning ;-)