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[209.85.220.65]) by mx.google.com with SMTPS id 200sor150927ybn.6.2019.05.14.17.16.31 for (Google Transport Security); Tue, 14 May 2019 17:16:31 -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=Ii41x4BP; 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=n6UubTu1HxL5JVqa4cIS4IiqN2UOsI0+Vavy5s5bkSQ=; b=Ii41x4BPQ69+lEiDQCtrEuc+lF56MxJAe2Nu9E3XbvbR4rUAzOZNAXuAlZRNS6P1H0 g1yyCvGfKBvZs2+YsXBIRXAAt9TKkYkQT8esPIAPxIMrzkMFFDmkcCGxuibr51tDIoEf hOvtu0p5Qti7QFT1qMeD2cxKaHTYxfMIvR16MTXd+gcnStMT2TE8onV6SNVb465wsnXH wJp8kOMWTtX8IzL1/yOc8GesomdBPegBNpb3c6rVynA4KMxgNmF6NSTnPBOPUCewSG7b unooTfA0p8UWmIEaIJ3dtmy1DpodFr7a94oCGmib2FAfj7Xgdla1FlVXjyqxjZB9wq8E /Ang== X-Google-Smtp-Source: APXvYqwXpG8BpCaAhxMLZu1bQsUf0ZlBvmb6V18GIGFeDsrDFmUXX3NvR6sEHYqBkd0VzopGg8Iw+LuwYseyH2LTLrI= X-Received: by 2002:a25:ad11:: with SMTP id y17mr18143295ybi.393.1557879391180; Tue, 14 May 2019 17:16:31 -0700 (PDT) MIME-Version: 1.0 References: <20190514213940.2405198-1-guro@fb.com> <20190514213940.2405198-8-guro@fb.com> In-Reply-To: <20190514213940.2405198-8-guro@fb.com> From: Shakeel Butt Date: Tue, 14 May 2019 17:16:19 -0700 Message-ID: Subject: Re: [PATCH v4 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: Tue, May 14, 2019 at 2:54 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 Reviewed-by: Shakeel Butt > --- > mm/memcontrol.c | 5 ++++- > mm/slab.h | 25 +++++++++++++++++++++++++ > mm/slab_common.c | 1 + > 3 files changed, 30 insertions(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 0655639433ed..9b2413c2e9ea 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 (PageHead(page) && 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 7ba50e526d82..50fa534c0fc0 100644 > --- a/mm/slab.h > +++ b/mm/slab.h > @@ -256,6 +256,26 @@ static inline struct kmem_cache *memcg_root_cache(struct kmem_cache *s) > return s->memcg_params.root_cache; > } > > +/* > + * Expects a pointer to a slab page. Please note, that PageSlab() check > + * isn't sufficient, as it returns true also for tail compound slab pages, > + * which do not have slab_cache pointer set. > + * So this function assumes that the page can pass PageHead() and PageSlab() > + * checks. > + */ > +static inline struct mem_cgroup *memcg_from_slab_page(struct page *page) > +{ > + struct kmem_cache *s; > + > + WARN_ON_ONCE(!rcu_read_lock_held()); > + > + s = READ_ONCE(page->slab_cache); > + if (s && !is_root_cache(s)) > + return rcu_dereference(s->memcg_params.memcg); > + > + return NULL; > +} > + > /* > * Charge the slab page belonging to the non-root kmem_cache. > * Can be called for non-root kmem_caches only. > @@ -353,6 +373,11 @@ 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 354762394162..9d2a3d6245dc 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -254,6 +254,7 @@ 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 >