linux-kernel - Re: [PATCH] Remove broken by design and by implementation devtmpfs maintenance disaster

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Date:	Fri, 18 Sep 2009 16:09:44 +0200
From:	Arjan van de Ven <arjan@...radead.org>
To:	ebiederm@...ssion.com (Eric W. Biederman)
Cc:	Kay Sievers <kay.sievers@...y.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Greg Kroah-Hartmann <greg@...ah.com>
Subject: Re: [PATCH] Remove broken by design and by implementation devtmpfs
  maintenance disaster

On Fri, 18 Sep 2009 06:54:39 -0700
ebiederm@...ssion.com (Eric W. Biederman) wrote:

> 
> > I don't understand. Udev applies the final policy including
> > permissions/ownership, just as before. There is no differrence. It's
> > just that you can bring up a box without complex userspace to
> > bootstrap /dev. And that's a big win on its own.
> 
> udev is too complex to use?  That sounds like a userspace bug.
> 
> This I guess is where I am baffled.   The argument for devtmpfs
> always seem to boil down to: udev sucks let's write some kernel
> code instead.
> 
> I have been trying to ask for a long time why we can't just fix
> udev to not suck. 
> 
> >  And things like
> > "modprobe loop; losetup /dev/loop0" will just work, which it doesn't
> > with todays async udev. Again, please make yourself familiar how
> > things work, and what the problems are.
> 
> I guess I don't understand why 
> modprobe loop; losetup /dev/loop0 is an interesting case.
> When you can just as easily do:
> modprobe loop; udevadm settle; losetup /dev/loop0.

frankly, modprobe should call the settle.
And not just this one, but we can use this to settle other things as
well... and then it can get an --async command line option for the
cases where you know you don't want to synchronize.


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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