Date: Thu, 8 Jan 2004 00:40:34 +0100 (CET)
From: Jesper Juhl <juhl-lkml@dif.dk>
To: Mike Fedyk <mfedyk@matchmail.com>
cc: Mike Waychison <Michael.Waychison@Sun.COM>,
       "H. Peter Anvin" <hpa@zytor.com>, linux-kernel@vger.kernel.org
Subject: Re: [autofs] [RFC] Towards a Modern Autofs
In-Reply-To: <20040107211134.GR1882@matchmail.com>
Message-ID: <Pine.LNX.4.56.0401080032570.9700@jju_lnx.backbone.dif.dk>
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 <m3ad50tmlq.fsf@averell.firstfloor.org> <3FFC46EB.9050201@zytor.com>
 <3FFC7469.3050700@sun.com> <20040107211134.GR1882@matchmail.com>
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On Wed, 7 Jan 2004, Mike Fedyk wrote:

> On Wed, Jan 07, 2004 at 04:04:41PM -0500, Mike Waychison wrote:
> > H. Peter Anvin wrote:
> >
> > >>Also when /home or other important fs are mounted via autofs there is
> > >>not much practical difference between a hung kernel and a hung
> > >>daemon. You have to reboot the system anyways.
> > >
> > >
> > >a) Guess which one is easier to debug?
> >
> > When they may both equally hang your machine, neither.
>
> Let's see.
>
> If it's in userspace, then setup your debug area in an area your system
> doesn't depend on, and wham, the hang won't affect the entire system anymore.
>
> Also, if you have /home automounted then it only affects the users on /home,
> and root's $home should be /home...
>

>From a user point of view I have to agree with you. Keeping it out of the
kernel makes perfect sense to me.

Easier to test your setup - errors will not hang the box.

In the case the implementation is buggy a daemon can easily be restarted
nightly without disrupting other things running on the box (a nightly
reboot is not as friendly).


>From a developer point of view, I also agree.

Debugging kernel code is in general a much harder thing to do than
debugging a userspace daemon. I'd also guess that more people will be
inclined to contribute development time to a userspace program than a
kernel based implementation - just the fact that it's in-kernel will be
percieved as having a much higher barrier-to-entry and I suspect that fact
alone might discourage potential contributers.


- Jesper Juhl

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