linux-kernel - Re: [PATCH] proc: move proc mount options out of pid

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Date:	Fri, 24 May 2013 04:29:54 +0000
From:	Stephen Mell <sub.atomic.fusion@...il.com>
To:	Gu Zheng <guz.fnst@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] proc: move proc mount options out of pid_namespace

Gu,

On Friday, May 24, 2013 11:03:31 Gu Zheng wrote:
> Hi Stephen,
> 
> On 05/24/2013 07:32 AM, Stephen Mell wrote:
> 
> > On Thursday, May 23, 2013 18:20:57 Gu Zheng wrote:
> > 
> >> Here it'll create a new proc sb instance which holds the same context as the old ones
> >> each time we mount proc though in the same PID namespace, won't it?
> > I believe so. But this is the point, right? 

> Yes, but I think it's also the problem.
> 
> >They won't be identical if different mount options are used, I don't think.
> 
> If different mount options are used, we'll create different super block instance, and they have
> the same context, only the difference is each one holds different proc_sb_info.
> But I think what we really want is only one proc sb instance and create different proc_sb_info
> if different mount options are used.

Will having several different superblocks cause problems, or is it merely inefficient? I freely admit to not really knowing what I'm doing, and I thank you for your assistance.
How is this situation distinct from that of ramfs? It appears to have a superblock for each mount.
It would seem to me as though one cannot have different sb_infos with the same superblock, making storing the mount options in sb_info effectively the same as storing them in the superblock itself, for the purposes of this discussion. Where would the mount options be stored, if not in the superblock?

> > 
> >> Here the pre-check seems needless.
> > Is that new with my patch, or has it always been needless?
> 
> Yeah, it's always needless.
> 
> Thanks,
> Gu
> 
> > 
> > Thanks,
> > Stephen

Thanks again,
Stephen
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