Re: [RFC][PATCH 1/8] namespace: use global namespace semaphore

[Mike Waychison <mike@waychison.com>]

Ian Kent wrote:
> On Tue, 31 May 2005, Miklos Szeredi wrote:
> 
> 
>>>There's not really anything magic about using the follow link method. It's 
>>>just a bit of a cheat as a directory can't also be a symlink and the 
>>>callback comes at exactly the right time to make stuff happen.
>>
>>So is it something like this?
>>
>>  - autofs is mounted over direct mountpoint 'dm'
>>
>>  - when dm is looked up, autofs's follow_link method is called
>>
>>  - this triggers the actual mount in the daemon, which mounts over
>>    the autofs filesystem (with some trick to avoid recursion)
> 
> 
> Admit, I haven't paid enough attention to recursion.
> Ouch! Caught by that the other day.
> 
> 
>>  - when the daemon is finished, the autofs's follow_link method
>>    enters the new mount (how?) and returns
> 
> 
> A function functionally similar to follow_mount of namei.c. Which needs 
> the appropriate vfsmount.
> 
> 
>>
>>Why do you need the mount topology for this?
> 
> 
> Don't. Actually need the nameidata upto date when the follow_link method 
> is called.
> 

However you can't rely on this for expiry checks, as the vfsmount can 
change (--rbind, CLONE_NEWNS).

Mike Waychison