Re: [PATCH v2 2/2] slub: Add method to verify memory is not freed.

[Ben Greear]

On 07/01/2011 07:11 AM, Christoph Lameter wrote:
> On Tue, 28 Jun 2011, greearb@xxxxxxxxxxxxxxx wrote:
>
> > diff --git a/include/linux/slab.h b/include/linux/slab.h
> > index ad4dd1c..916ce0f 100644
> > --- a/include/linux/slab.h
> > +++ b/include/linux/slab.h
> > @@ -302,6 +302,19 @@ extern void *__kmalloc_node_track_caller(size_t, gfp_t, int, unsigned long);
> >
> >   #endif /* CONFIG_NUMA */
> >
> > +/**
> > + * Calling this on allocated memory will check that the memory
> > + * is expected to be in use, and print warnings if not.
> > + */
> > +#if defined(CONFIG_SLUB)&&  defined(CONFIG_SLUB_DEBUG)
> > +extern bool verify_mem_not_deleted(const void *x);
> > +#else
> > +static inline bool verify_mem_not_deleted(const void *x)
> > +{
> > +	return true;
> > +}
> > +#endif
> > +
>
> Why is this in slab.h and not slub_def.h?

No reason..I'll move it.

> > diff --git a/mm/slub.c b/mm/slub.c
> > index 3477ce5..f64caca 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -2958,6 +2958,42 @@ size_t ksize(const void *object)
> >   }
> >   EXPORT_SYMBOL(ksize);
> >
> > +#ifdef CONFIG_SLUB_DEBUG
> > +bool verify_mem_not_deleted(const void *x)
> > +{
> > +	struct page *page;
> > +	void *object = (void *)x;
> > +	unsigned long flags;
> > +	bool rv;
> > +
> > +	if (unlikely(ZERO_OR_NULL_PTR(x)))
> > +		return false;
> > +
> > +	local_irq_save(flags);
> > +
> > +	page = virt_to_head_page(x);
> > +	if (unlikely(!PageSlab(page))) {
> > +		/* maybe it was from stack? */
> > +		rv = true;
> > +		goto out_unlock;
> > +	}
>
> The above check is problematic for slabs that have SLAB_DESTROY_BY_RCU
> set. PageSlab(page) may be true to the next rcu interval.

Well, any suggestions on how to do this better?

Thanks,
Ben

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--
Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc  http://www.candelatech.com
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