linux-kernel - Re: [PATCH v4 5/7] mm, kasan: Stackdepot implementation. Enable stackdepot for SLAB

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Date:	Fri, 11 Mar 2016 11:10:34 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Andrey Ryabinin <ryabinin.a.a@...il.com>
Cc:	Alexander Potapenko <glider@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Andrey Konovalov <adech.fo@...il.com>,
	Christoph Lameter <cl@...ux.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	JoonSoo Kim <js1304@...il.com>,
	Kostya Serebryany <kcc@...gle.com>,
	kasan-dev <kasan-dev@...glegroups.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH v4 5/7] mm, kasan: Stackdepot implementation. Enable
 stackdepot for SLAB

On Fri, 11 Mar 2016 14:43:45 +0300
Andrey Ryabinin <ryabinin.a.a@...il.com> wrote:


> >> This is not about size, this about fragmentation. vmalloc allows to
> >> utilize available low-order pages,
> >> hence reduce the fragmentation.  
> > I've attempted to add __vmalloc(STACK_ALLOC_SIZE, alloc_flags,
> > PAGE_KERNEL) (also tried vmalloc(STACK_ALLOC_SIZE)) instead of
> > page_alloc() and am now getting a crash in
> > kmem_cache_alloc_node_trace() in mm/slab.c, because it doesn't allow
> > the kmem_cache pointer to be NULL (it's dereferenced when calling
> > trace_kmalloc_node()).
> > 
> > Steven, do you know if this because of my code violating some contract
> > (e.g. I'm calling vmalloc() too early, when kmalloc_caches[] haven't
> > been initialized),   
> 
> Probably. kmem_cache_init() goes before vmalloc_init().

Agreed, that function can not be called with cachep NULL, nor can it be
called before kmem_cache is set up to point to kmem_cache_boot.

-- Steve