Re: [autofs] [RFC] Towards a Modern Autofs

[Mike Waychison <Michael.Waychison@Sun.COM>]

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Jeff Garzik wrote:
> Mike Waychison wrote:
> 
>> To put it into perspective, the I'm calling for the following major 
>> changes:
> 
> [...]
> 
>> 2) move the loop that used to spin around and ask kernelspace if there 
>> was anything to expire into the VFS as well, where it won't be killed.
> 
> [...]
> 
>> (1) and (2) shouldn't be hard at all to do considering David Howells 
>> has done the majority of this already. (3) is needed in order to 
>> manage direct mounts properly for when they are 'covered'.  
>> Admittedly, (4) comes off as an ugly hack.
>>
>> Also, (2) was the only 'active' task the automount daemon was doing. 
>> Everything else it did can be rewritten in the form of a usermode 
>> helper that runs only when it is needed.  This simplifies the 
>> userspace code a lot.
> 
> 
> Just going by your own explanation here, #2 should not be in the kernel.
> 
> If we moving daemons into the kernel just because they won't be killed, 
> we'll have Oracle in-kernel before you know it.  Completely spurious 
> reason.
> 

You wouldn't put a bdflush daemon in userspace either would you?  The 
loop in question is just that; (overly simplified):

while (1) {
	f = ask_kernel_if_anything_looks_inactive();
	if (f) {
		try_to_umount(f);
		continue;
	} else {
		sleep(x seconds);
	}
}

My point is, if this is the only active action done by userspace, why 
open it up to being broken?

-- 
Mike Waychison
Sun Microsystems, Inc.
1 (650) 352-5299 voice
1 (416) 202-8336 voice
mailto: Michael.Waychison@Sun.COM
http://www.sun.com

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