linux-kernel - Re: [PATCH] slub: correctly bootstrap boot caches

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Date:	Fri, 22 Feb 2013 19:45:14 +0400
From:	Glauber Costa <glommer@...allels.com>
To:	Christoph Lameter <cl@...ux.com>
CC:	<linux-mm@...ck.org>, <cgroups@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>, Pekka Enberg <penberg@...nel.org>,
	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH] slub: correctly bootstrap boot caches

On 02/22/2013 07:39 PM, Christoph Lameter wrote:
> On Fri, 22 Feb 2013, Glauber Costa wrote:
> 
>> As I've mentioned in the description, the real bug is from partial slabs
>> being temporarily in the cpu_slab during a recent allocation and
>> therefore unreachable through the partial list.
> 
> The bootstrap code does not use cpu slabs but goes directly to the slab
> pages. See early_kmem_cache_node_alloc.
> 

That differs from what I am seeing here.
I can trace an early __slab_alloc allocation from
the kmem_cache_node cache, very likely coming from the kmem_cache boot
cache creation. It takes the page out of the partial list and moves it
to the cpu_slab. After that, that particular page becomes unreachable
for bootstrap.

At this point, we are already slab_state == PARTIAL, while
init_kmem_cache_nodes will only differentiate against slab_state == DOWN.



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