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

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Date:	Fri, 22 Feb 2013 20:15:48 +0900
From:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Glauber Costa <glommer@...allels.com>
CC:	linux-mm@...ck.org, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org, Christoph Lameter <cl@...ux.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>, Pekka Enberg <penberg@...nel.org>
Subject: Re: [PATCH] slub: correctly bootstrap boot caches

(2013/02/22 19:30), Glauber Costa wrote:
> After we create a boot cache, we may allocate from it until it is bootstraped.
> This will move the page from the partial list to the cpu slab list. If this
> happens, the loop:
> 
> 	list_for_each_entry(p, &n->partial, lru)
> 
> that we use to scan for all partial pages will yield nothing, and the pages
> will keep pointing to the boot cpu cache, which is of course, invalid. To do
> that, we should flush the cache to make sure that the cpu slab is back to the
> partial list.
> 
> Although not verified in practice, I also point out that it is not safe to scan
> the full list only when debugging is on in this case. As unlikely as it is, it
> is theoretically possible for the pages to be full. If they are, they will
> become unreachable. Aside from scanning the full list, we also need to make
> sure that the pages indeed sit in there: the easiest way to do it is to make
> sure the boot caches have the SLAB_STORE_USER debug flag set.
> 
> Signed-off-by: Glauber Costa <glommer@...allels.com>
> Reported-by:  Steffen Michalke <StMichalke@....de>
> Cc: Christoph Lameter <cl@...ux.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Pekka Enberg <penberg@...nel.org>
> Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> 
You're quick :) the issue is fixed in my environ.

Tested-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu,com>


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