Re: [PATCH mm] kfence, slab: fix cache_alloc_debugcheck_after() for bulk allocations

[Andrew Morton]

On Thu, 4 Mar 2021 22:05:48 +0100 Alexander Potapenko <glider@xxxxxxxxxx> wrote:

> On Thu, Mar 4, 2021 at 9:53 PM Marco Elver <elver@xxxxxxxxxx> wrote:
> >
> > cache_alloc_debugcheck_after() performs checks on an object, including
> > adjusting the returned pointer. None of this should apply to KFENCE
> > objects. While for non-bulk allocations, the checks are skipped when we
> > allocate via KFENCE, for bulk allocations cache_alloc_debugcheck_after()
> > is called via cache_alloc_debugcheck_after_bulk().
> 
> @Andrew, is this code used by anyone?
> As far as I understand, it cannot be enabled by any config option, so
> nobody really tests it.
> If it is still needed, shall we promote #if DEBUGs in slab.c to a
> separate config option, or maybe this code can be safely removed?

It's all used:

#ifdef CONFIG_DEBUG_SLAB
#define	DEBUG		1
#define	STATS		1
#define	FORCED_DEBUG	1
#else
#define	DEBUG		0
#define	STATS		0
#define	FORCED_DEBUG	0
#endif