On Dec 2, 2013, at 3:12, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
> On Sun, Dec 01, 2013 at 06:13:29PM +0000, Al Viro wrote:
>> Making the series no-go in that form, obviously.
>
> Looking at the mess it made I'd almost be tempted to say a little leak
> for a less used features is better than lots of pain for everyone..
>
> Looking at the mess it made I'm really upset.
>
>>> Given that the namespace kraken has infected various internal filesystem
>>> and will get more soon I suspect this problem is or will become generic
>>> and will need a proper solution anyway. Al, any good ideas how to deal
>>> with this? Most straight forward way would be to add a counter of
>>> user vfsmount to the superblock and methods when it goes to 1 and 0,
>>> but that seems a bit ugly.
>>
>> Folks, please, _please_, let's formulate the lifecycle rules first; we
>> already had way too much trouble from putting mechanism first only to
>> run into questions like the above ("what happens if somebody tries to
>> allocate a PID in pid_ns that is already scheduled for shutdown?").
>> Remember the (recurring) fun with kobject-related lifetime issues?
>> Or rpc_pipefs notifier ugliness, for that matter...
>
> I'll have to let the net namespace folks chime in for that, as far as
> I'm concerned it's a featured better config'ed off. If they can't come
> up with anything better the procfs hack above would be it.
The lifetime of the kernel mount only needs to match that of the rpc_client, since each rpc_client is associated to a single net namespace, and each net namespace is in a 1-1 relationship with an rpc_pipefs super block.
IOW: move the kernel mount/umount back to the rpc_client create/destroy methods and all should be well.
Cheers
Trond--
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