netdev - Re: [MM PATCH V4 5/6] slub: support for bulk free with SLUB freelists

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Date:	Tue, 29 Sep 2015 20:16:05 +0200
From:	Jesper Dangaard Brouer <brouer@...hat.com>
To:	Alexander Duyck <alexander.duyck@...il.com>
Cc:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux.com>, netdev@...r.kernel.org,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>, brouer@...hat.com
Subject: Re: [MM PATCH V4 5/6] slub: support for bulk free with SLUB
 freelists

On Tue, 29 Sep 2015 10:20:20 -0700
Alexander Duyck <alexander.duyck@...il.com> wrote:

> On 09/29/2015 10:00 AM, Jesper Dangaard Brouer wrote:
> > On Tue, 29 Sep 2015 09:38:30 -0700
> > Alexander Duyck <alexander.duyck@...il.com> wrote:
> >
> >> On 09/29/2015 08:48 AM, Jesper Dangaard Brouer wrote:
> >>> +#if defined(CONFIG_KMEMCHECK) ||		\
> >>> +	defined(CONFIG_LOCKDEP)	||		\
> >>> +	defined(CONFIG_DEBUG_KMEMLEAK) ||	\
> >>> +	defined(CONFIG_DEBUG_OBJECTS_FREE) ||	\
> >>> +	defined(CONFIG_KASAN)
> >>> +static inline void slab_free_freelist_hook(struct kmem_cache *s,
> >>> +					   void *head, void *tail)
> >>> +{
> >>> +	void *object = head;
> >>> +	void *tail_obj = tail ? : head;
> >>> +
> >>> +	do {
> >>> +		slab_free_hook(s, object);
> >>> +	} while ((object != tail_obj) &&
> >>> +		 (object = get_freepointer(s, object)));
> >>> +}
> >>> +#else
> >>> +static inline void slab_free_freelist_hook(struct kmem_cache *s, void *obj_tail,
> >>> +					   void *freelist_head) {}
> >>> +#endif
> >>> +
> >> Instead of messing around with an #else you might just wrap the contents
> >> of slab_free_freelist_hook in the #if/#endif instead of the entire
> >> function declaration.
> >
> > I had it that way in an earlier version of the patch, but I liked
> > better this way.
> 
> It would be nice if the argument names were the same for both cases.  
> Having the names differ will make it more difficult to maintain when 
> changes need to be made to the function.

Nice spotted, I forgot to change arg names of the empty function, when
I updated the patch. Guess, it is an argument for moving the "if
defined()" into the function body.

It just looked strange to have such a big ifdef block inside the
function.  I also earlier had it define another def and use that inside
the function, but then the code-reader would not know if this new def
was/could-be used later (nitpicking alert...)

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer
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