linux-kernel - Re: [PATCH v3 4/5] mm: kmem: scoped objcg protection

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Message-ID: <549f20e0-d0d7-b379-6725-4f76dddcd6fc@suse.cz>
Date:   Wed, 18 Oct 2023 16:04:59 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Roman Gushchin <roman.gushchin@...ux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>, shakeelb@...gle.com,
        Muchun Song <muchun.song@...ux.dev>,
        Dennis Zhou <dennis@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Naresh Kamboju <naresh.kamboju@...aro.org>
Subject: Re: [PATCH v3 4/5] mm: kmem: scoped objcg protection

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@...ux.dev>
> Tested-by: Naresh Kamboju <naresh.kamboju@...aro.org>
> Acked-by: Shakeel Butt <shakeelb@...gle.com>

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