linux-kernel - Re: [PATCH 1/3] slub: correct to calculate num of acquired objects in get_partial

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Message-ID: <0000013c3ee3b69a-80cfdc68-a753-44e0-ba68-511060864128-000000@email.amazonses.com>
Date:	Tue, 15 Jan 2013 15:46:17 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
cc:	Pekka Enberg <penberg@...nel.org>, js1304@...il.com,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] slub: correct to calculate num of acquired objects
 in get_partial_node()

On Tue, 15 Jan 2013, Joonsoo Kim wrote:

> There is a subtle bug when calculating a number of acquired objects.
> After acquire_slab() is executed at first, page->inuse is same as
> page->objects, then, available is always 0. So, we always go next
> iteration.

page->inuse is always < page->objects because the partial list is not used
for slabs that are fully allocated. page->inuse == page->objects means
that no objects are available on the slab and therefore the slab would
have been removed from the partial list.

> After that, we don't need return value of put_cpu_partial().
> So remove it.

Hmmm... The code looks a bit easier to understand than what we have right now.

Could you try to explain it better?
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