linux-kernel - Re: [PATCH 1/7][QUOTA] Move sysctl management code under ifdef CONFIG

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Message-Id: <20071204014549.8fe47f7f.akpm@linux-foundation.org>
Date:	Tue, 4 Dec 2007 01:45:49 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Pavel Emelyanov <xemul@...nvz.org>
Cc:	ebiederm@...ssion.com, linux-kernel@...r.kernel.org,
	devel@...nvz.org
Subject: Re: [PATCH 1/7][QUOTA] Move sysctl management code under ifdef
 CONFIG_SYSCTL

On Tue, 04 Dec 2007 12:31:37 +0300 Pavel Emelyanov <xemul@...nvz.org> wrote:

> Andrew Morton wrote:
> > On Tue, 04 Dec 2007 11:58:30 +0300 Pavel Emelyanov <xemul@...nvz.org> wrote:
> > 
> >>>> +#ifdef CONFIG_SYSCTL
> >>>>  	register_sysctl_table(sys_table);
> >>>> +#endif
> >>>>  
> >>>>  	dquot_cachep = kmem_cache_create("dquot",
> >>>>  			sizeof(struct dquot), sizeof(unsigned long) * 4,
> >>> We should avoid the ifdefs around the register_sysctl_table() call.
> >>>
> >>> At present the !CONFIG_SYSCTL implementation of register_sysctl_table() is
> >>> a non-inlined NULL-returning stub.  All we have to do is to inline that stub
> >>> then these ifdefs can go away.
> >> What if some code checks for the return value to be not-NULL? In case
> >> CONFIG_SYSCTL=n this code will always think, that the registration failed.
> > 
> > The stub function should return success?
> 
> Well, I think yes. If some functionality is turned off, then the 
> caller should think that everything is going fine (or he should
> explicitly removes the call to it with some other ifdef). 
> 
> At least this is true for stubs that return the error code, not 
> the pointer. E.g. copy_semundo() always returns success if SYSVIPC 
> is off, or namespaces cloning routines act in a similar way.
> 
> Thus I though, that routines, that return pointers should better
> report that everything is OK (somehow) to reduce the number of 
> "helpers" in the outer code. No?
> 

Dunno.  Returning NULL should be OK.  If anyone is dereferenceing that
pointer with CONFIG_SYSCTL=n then they might need some attention?  
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