linux-kernel - Re: [RFC PATCH 2/3] kmemleak: Add callbacks to the bootmem allocator

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Date:	Tue, 7 Jul 2009 18:53:50 +0200
From:	Johannes Weiner <hannes@...xchg.org>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	Catalin Marinas <catalin.marinas@....com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>
Subject: Re: [RFC PATCH 2/3] kmemleak: Add callbacks to the bootmem allocator

On Tue, Jul 07, 2009 at 10:08:50AM +0300, Pekka Enberg wrote:
> On Mon, 2009-07-06 at 11:51 +0100, Catalin Marinas wrote:
> > This patch adds kmemleak_alloc/free callbacks to the bootmem allocator.
> > This would allow scanning of such blocks and help avoiding a whole class
> > of false positives and more kmemleak annotations.
> > 
> > Signed-off-by: Catalin Marinas <catalin.marinas@....com>
> > Cc: Ingo Molnar <mingo@...e.hu>
> > Cc: Pekka Enberg <penberg@...helsinki.fi>
> 
> Looks good to me!
> 
> Acked-by: Pekka Enberg <penberg@...helsinki.fi>
> 
> But lets cc Johannes on this too.

> > @@ -597,7 +601,9 @@ restart:
> >  void * __init __alloc_bootmem_nopanic(unsigned long size, unsigned long align,
> >  					unsigned long goal)
> >  {
> > -	return ___alloc_bootmem_nopanic(size, align, goal, 0);
> > +	void *ptr =  ___alloc_bootmem_nopanic(size, align, goal, 0);
> > +	kmemleak_alloc(ptr, size, 1, GFP_KERNEL);
> > +	return ptr;

You may get an object from kzalloc() here, I don't think you want to
track that (again), right?

Pekka already worked out all the central places to catch 'slab already
available' allocations, they can probably help you place the hooks.

> >  static void * __init ___alloc_bootmem(unsigned long size, unsigned long align,
> > @@ -631,7 +637,9 @@ static void * __init ___alloc_bootmem(unsigned long size, unsigned long align,
> >  void * __init __alloc_bootmem(unsigned long size, unsigned long align,
> >  			      unsigned long goal)
> >  {
> > -	return ___alloc_bootmem(size, align, goal, 0);
> > +	void *ptr = ___alloc_bootmem(size, align, goal, 0);
> > +	kmemleak_alloc(ptr, size, 1, GFP_KERNEL);
> > +	return ptr;

Same here.

> >  #ifdef CONFIG_SPARSEMEM
> > @@ -707,14 +719,18 @@ void * __init __alloc_bootmem_node_nopanic(pg_data_t *pgdat, unsigned long size,
> >  		return kzalloc_node(size, GFP_NOWAIT, pgdat->node_id);
> >  
> >  	ptr = alloc_arch_preferred_bootmem(pgdat->bdata, size, align, goal, 0);
> > +	kmemleak_alloc(ptr, size, 1, GFP_KERNEL);
> >  	if (ptr)
> >  		return ptr;
> >  
> >  	ptr = alloc_bootmem_core(pgdat->bdata, size, align, goal, 0);
> > +	kmemleak_alloc(ptr, size, 1, GFP_KERNEL);
> >  	if (ptr)
> >  		return ptr;
> >  
> > -	return __alloc_bootmem_nopanic(size, align, goal);
> > +	ptr = __alloc_bootmem_nopanic(size, align, goal);
> > +	kmemleak_alloc(ptr, size, 1, GFP_KERNEL);
> > +	return ptr;
> >  }

Can you use a central exit and goto?

> >  #ifndef ARCH_LOW_ADDRESS_LIMIT
> > @@ -737,7 +753,9 @@ void * __init __alloc_bootmem_node_nopanic(pg_data_t *pgdat, unsigned long size,
> >  void * __init __alloc_bootmem_low(unsigned long size, unsigned long align,
> >  				  unsigned long goal)
> >  {
> > -	return ___alloc_bootmem(size, align, goal, ARCH_LOW_ADDRESS_LIMIT);
> > +	void *ptr =  ___alloc_bootmem(size, align, goal, ARCH_LOW_ADDRESS_LIMIT);
> > +	kmemleak_alloc(ptr, size, 1, GFP_KERNEL);
> > +	return ptr;
> >  }

Possible slab object.

> > @@ -758,9 +776,13 @@ void * __init __alloc_bootmem_low(unsigned long size, unsigned long align,
> >  void * __init __alloc_bootmem_low_node(pg_data_t *pgdat, unsigned long size,
> >  				       unsigned long align, unsigned long goal)
> >  {
> > +	void *ptr;
> > +
> >  	if (WARN_ON_ONCE(slab_is_available()))
> >  		return kzalloc_node(size, GFP_NOWAIT, pgdat->node_id);
> >  
> > -	return ___alloc_bootmem_node(pgdat->bdata, size, align,
> > -				goal, ARCH_LOW_ADDRESS_LIMIT);
> > +	ptr = ___alloc_bootmem_node(pgdat->bdata, size, align,
> > +				    goal, ARCH_LOW_ADDRESS_LIMIT);
> > +	kmemleak_alloc(ptr, size, 1, GFP_KERNEL);

These GFP_KERNEL startled me.  We know for sure that this code runs in
earlylog mode only and gfp is unused, right?  Can you perhaps just
pass 0 for gfp instead?

	Hannes
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