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Date:   Wed, 18 Oct 2023 16:04:59 +0200
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Subject: Re: [PATCH v3 4/5] mm: kmem: scoped objcg protection
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To:     Roman Gushchin <roman.gushchin@linux.dev>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
        Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>, shakeelb@google.com,
        Muchun Song <muchun.song@linux.dev>,
        Dennis Zhou <dennis@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Naresh Kamboju <naresh.kamboju@linaro.org>
References: <20231016221900.4031141-1-roman.gushchin@linux.dev>
 <20231016221900.4031141-5-roman.gushchin@linux.dev>
From:   Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <20231016221900.4031141-5-roman.gushchin@linux.dev>
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On 10/17/23 00:18, Roman Gushchin wrote:
> Switch to a scope-based protection of the objcg pointer on slab/kmem
> allocation paths. Instead of using the get_() semantics in the
> pre-allocation hook and put the reference afterwards, let's rely
> on the fact that objcg is pinned by the scope.
> 
> It's possible because:
> 1) if the objcg is received from the current task struct, the task is
>    keeping a reference to the objcg.
> 2) if the objcg is received from an active memcg (remote charging),
>    the memcg is pinned by the scope and has a reference to the
>    corresponding objcg.
> 
> Signed-off-by: Roman Gushchin (Cruise) <roman.gushchin@linux.dev>
> Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
> Acked-by: Shakeel Butt <shakeelb@google.com>

Reviewed-by: Vlastimil Babka <vbabka@suse.cz>