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[209.85.220.65]) by mx.google.com with SMTPS id w206sor2946181ywb.171.2019.05.10.17.34.19 for (Google Transport Security); Fri, 10 May 2019 17:34:19 -0700 (PDT) Received-SPF: pass (google.com: domain of shakeelb@google.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=ldjw+nnH; spf=pass (google.com: domain of shakeelb@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=shakeelb@google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=UdR8JD8KNYcClfaFJdc0xlMZRTEn4yngxUY4SL7WlW0=; b=ldjw+nnHKtK+fTb3weGK94cuP7qxL2t2RlNOFIukoBDh3zAGfoairpjWMbIy5l0awC Cme3/bk3ny+bZNg+Sk7MaNgjTzhXOTneCTyRQFxQFgkDjo+F43dfkwIAhr2ZDouf1ews ujrOSdkBOctfat+ir1VYjVQlB0jBB99jcYRj0lyEITB/Gf2XJgd3ff8voLr+y2opCB/C n4J26cguL50D8zOOjX+oxASqm3If2L17oo63Q8Jn+fD2R36iAm/rUY6vb5zRAUKQbHYH X5OWy/+DZyxzP1ozyftiL0Tx8uW2O7TiguDuR848V0mrs0l+HQDsrETH2rnVapR2eryN +1TQ== X-Google-Smtp-Source: APXvYqzMzoHGg899Vyb0ItflS72q8KkTnThgd/WORnQ3DVf4ygp5Lx6Lfya9tCIS3swbhrAwy7E449I3E1e5y2H8Xs0= X-Received: by 2002:a0d:ff82:: with SMTP id p124mr7980895ywf.409.1557534859480; Fri, 10 May 2019 17:34:19 -0700 (PDT) MIME-Version: 1.0 References: <20190508202458.550808-1-guro@fb.com> <20190508202458.550808-8-guro@fb.com> In-Reply-To: <20190508202458.550808-8-guro@fb.com> From: Shakeel Butt Date: Fri, 10 May 2019 17:34:08 -0700 Message-ID: Subject: Re: [PATCH v3 7/7] mm: fix /proc/kpagecgroup interface for slab pages To: Roman Gushchin Cc: Andrew Morton , Linux MM , LKML , Kernel Team , Johannes Weiner , Michal Hocko , Rik van Riel , Christoph Lameter , Vladimir Davydov , Cgroups Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Roman Gushchin Date: Wed, May 8, 2019 at 1:40 PM To: Andrew Morton, Shakeel Butt Cc: , , , Johannes Weiner, Michal Hocko, Rik van Riel, Christoph Lameter, Vladimir Davydov, , Roman Gushchin > Switching to an indirect scheme of getting mem_cgroup pointer for > !root slab pages broke /proc/kpagecgroup interface for them. > > Let's fix it by learning page_cgroup_ino() how to get memcg > pointer for slab pages. > > Reported-by: Shakeel Butt > Signed-off-by: Roman Gushchin > --- > mm/memcontrol.c | 5 ++++- > mm/slab.h | 21 +++++++++++++++++++++ > mm/slab_common.c | 1 + > 3 files changed, 26 insertions(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 6e4d9ed16069..8114838759f6 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -494,7 +494,10 @@ ino_t page_cgroup_ino(struct page *page) > unsigned long ino = 0; > > rcu_read_lock(); > - memcg = READ_ONCE(page->mem_cgroup); > + if (PageSlab(page)) > + memcg = memcg_from_slab_page(page); > + else > + memcg = READ_ONCE(page->mem_cgroup); > while (memcg && !(memcg->css.flags & CSS_ONLINE)) > memcg = parent_mem_cgroup(memcg); > if (memcg) > diff --git a/mm/slab.h b/mm/slab.h > index acdc1810639d..cb684fbe2cc2 100644 > --- a/mm/slab.h > +++ b/mm/slab.h > @@ -256,6 +256,22 @@ static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s) > return s->memcg_params.root_cache; > } > Can you please document the preconditions of this function? It seems like it must be PageSlab() then why need to check PageTail and do compound_head(). > +static inline struct mem_cgroup *memcg_from_slab_page(struct page *page) > +{ > + struct kmem_cache *s; > + > + WARN_ON_ONCE(!rcu_read_lock_held()); > + > + if (PageTail(page)) > + page = compound_head(page); > + > + s = READ_ONCE(page->slab_cache); > + if (s && !is_root_cache(s)) > + return rcu_dereference(s->memcg_params.memcg); > + > + return NULL; > +} > + > static __always_inline int memcg_charge_slab(struct page *page, > gfp_t gfp, int order, > struct kmem_cache *s) > @@ -338,6 +354,11 @@ static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s) > return s; > } > > +static inline struct mem_cgroup *memcg_from_slab_page(struct page *page) > +{ > + return NULL; > +} > + > static inline int memcg_charge_slab(struct page *page, gfp_t gfp, int order, > struct kmem_cache *s) > { > diff --git a/mm/slab_common.c b/mm/slab_common.c > index 36673a43ed31..0cfdad0a0aac 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -253,6 +253,7 @@ static void memcg_unlink_cache(struct kmem_cache *s) > list_del(&s->memcg_params.kmem_caches_node); > mem_cgroup_put(rcu_dereference_protected(s->memcg_params.memcg, > lockdep_is_held(&slab_mutex))); > + rcu_assign_pointer(s->memcg_params.memcg, NULL); > } > } > #else > -- > 2.20.1 >