linux-kernel - Re: [PATCH 1/3] Slab infrastructure for array operations

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Date:	Wed, 11 Feb 2015 12:18:07 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Christoph Lameter <cl@...ux.com>
cc:	akpm@...uxfoundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, penberg@...nel.org, iamjoonsoo@....com,
	Jesper Dangaard Brouer <brouer@...hat.com>
Subject: Re: [PATCH 1/3] Slab infrastructure for array operations

On Wed, 11 Feb 2015, Christoph Lameter wrote:

> > This patch is referencing functions that don't exist and can do so since
> > it's not compiled, but I think this belongs in the next patch.  I also
> > think that this particular implementation may be slub-specific so I would
> > have expected just a call to an allocator-defined
> > __kmem_cache_alloc_array() here with i = __kmem_cache_alloc_array().
> 
> The implementation is generic and can be used in the same way for SLAB.
> SLOB does not have these types of object though.
> 

Ok, I didn't know if the slab implementation would follow the same format 
with the same callbacks or whether this would need to be cleaned up later.  

> > return 0 instead of using _HAVE_SLAB_ALLOCATOR_ARRAY_OPERATIONS at all.
> 
> Ok that is a good idea. I'll just drop that macro and have all allocators
> provide dummy functions.
> 
> > > +#ifndef _HAVE_SLAB_ALLOCATOR_ARRAY_OPERATIONS
> > > +void kmem_cache_free_array(struct kmem_cache *s, size_t nr, void **p)
> > > +{
> > > +	__kmem_cache_free_array(s, nr, p);
> > > +}
> > > +EXPORT_SYMBOL(kmem_cache_free_array);
> > > +#endif
> > > +
> >
> > Hmm, not sure why the allocator would be required to do the
> > EXPORT_SYMBOL() if it defines kmem_cache_free_array() itself.  This
> 
> Keeping the EXPORT with the definition is the custom as far as I could
> tell.
> 

If you do dummy functions for all the allocators, then this should be as 
simple as unconditionally defining kmem_cache_free_array() and doing 
EXPORT_SYMBOL() here and then using your current implementation of 
__kmem_cache_free_array() for mm/slab.c.
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