linux-kernel - Re: [PATCH] mm,slab,memcg: call memcg kmem put cache with same condition as get

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Date:   Wed, 09 Jan 2019 09:09:49 -0500
From:   Rik van Riel <riel@...riel.com>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kernel-team@...com,
        Linux MM <linux-mm@...ck.org>, stable@...r.kernel.org,
        Alexey Dobriyan <adobriyan@...il.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Johannes Weiner <hannes@...xchg.org>, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH] mm,slab,memcg: call memcg kmem put cache with same
 condition as get

On Tue, 2019-01-08 at 21:36 -0800, Shakeel Butt wrote:
> On Tue, Jan 8, 2019 at 8:01 PM Rik van Riel <riel@...riel.com> wrote:
> > 
> > There is an imbalance between when slab_pre_alloc_hook calls
> > memcg_kmem_get_cache and when slab_post_alloc_hook calls
> > memcg_kmem_put_cache.
> > 
> 
> Can you explain how there is an imbalance? If the returned kmem cache
> from memcg_kmem_get_cache() is the memcg kmem cache then the refcnt
> of
> memcg is elevated and the memcg_kmem_put_cache() will correctly
> decrement the refcnt of the memcg.

Indeed, you are right. Never mind this patch.

Back to square one on that bug.

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