linux-kernel - Re: [PATCH TRIVIAL] mm: Fix build warning in kmem_cache

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Date:	Mon, 16 Jul 2012 09:56:16 -0600
From:	Shuah Khan <shuah.khan@...com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	David Rientjes <rientjes@...gle.com>,
	Pekka Enberg <penberg@...nel.org>, glommer@...allels.com,
	js1304@...il.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	shuahkhan@...il.com
Subject: Re: [PATCH TRIVIAL] mm: Fix build warning in kmem_cache_create()

On Mon, 2012-07-16 at 09:17 -0500, Christoph Lameter wrote:
> On Mon, 16 Jul 2012, David Rientjes wrote:
> 
> > On Sun, 15 Jul 2012, Shuah Khan wrote:
> >
> > > I can work on reshuffling the code. Do have a question though. This
> > > following sanity check is currently done only when CONFIG_DEBUG_VM is
> > > defined. However, it does appear to be something that is that should be
> > > checked even in regular path.
> > >
> > > struct kmem_cache *kmem_cache_create(const char *name, size_t size,
> > > size_t align,
> > >                 unsigned long flags, void (*ctor)(void *))
> > > {
> > >         struct kmem_cache *s = NULL;
> > >
> > > #ifdef CONFIG_DEBUG_VM
> > >         if (!name || in_interrupt() || size < sizeof(void *) ||
> > >                 size > KMALLOC_MAX_SIZE) {
> > >                 printk(KERN_ERR "kmem_cache_create(%s) integrity check"
> > >                         " failed\n", name);
> > >                 goto out;
> > >         }
> > > #endif
> > >
> >
> > Agreed, this shouldn't depend on CONFIG_DEBUG_VM.
> 
> These checks are useless for regular kernel operations. They are
> only useful when developing code and should only be enabled during
> development. There is no point in testing the size and the name which are
> typically constant when a slab is created with a stable kernel.
> 

ok. The first debug section is done prior to holding the slab mutex and
the second debug section is after holding mutex. I will have to think
about the best way to restructure the code. I will send the re-worked
patch soon, so we start refining it if need be.

-- Shuah

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