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From: Roman Gushchin To: Yafang Shao Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, kafai@fb.com, songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com, haoluo@google.com, jolsa@kernel.org, hannes@cmpxchg.org, mhocko@kernel.org, shakeelb@google.com, songmuchun@bytedance.com, akpm@linux-foundation.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH bpf-next 13/15] mm, memcg: Add new helper get_obj_cgroup_from_cgroup Message-ID: References: <20220810151840.16394-1-laoar.shao@gmail.com> <20220810151840.16394-14-laoar.shao@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220810151840.16394-14-laoar.shao@gmail.com> X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1660234611; a=rsa-sha256; cv=none; b=KaF8Hk+PDVfRmf+HoJ0sIEl+R+7p9Z3V4yBhMjfjHxt/DH7ZaIKm/k1oDQg4NaJi4pW/Gn sKg/c8ItAHp8ZFYpZ2aHAJ1OM6bEZ1okPx6CcW1avcQhl/SImCBOO5T6PA65I90rnUe7WX UrIqui0DqWRHuTbmnebgxfxPFiIXFnk= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=LGxJvmFF; spf=pass (imf21.hostedemail.com: domain of roman.gushchin@linux.dev designates 188.165.223.204 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1660234611; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=d9Knayh1uWBTa8dQn7LG9+/Wpow1M6VlJCr9CzUjIEk=; b=mR0gnJTgaYedUHT+eC7kzKh2b7hc5jcLNinrDfMX9zAllZGj2sP2Pb2/OY+0B3+fvLfAqu pLmQpq7cwKfH6dondUmwoutY+vR5/VCjR0sx/4r51X2PG2EYErnm7E55AkcI8zXn9SRhfa JEFXFFfkQfQIwFesqDyjgz/uvoMCtjo= X-Stat-Signature: ecwq817mf1irkqf4bgnjr61wpjjt5jnq X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 1F0A61C01BB Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=LGxJvmFF; spf=pass (imf21.hostedemail.com: domain of roman.gushchin@linux.dev designates 188.165.223.204 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev; dmarc=pass (policy=none) header.from=linux.dev X-Rspam-User: X-HE-Tag: 1660234610-817337 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: On Wed, Aug 10, 2022 at 03:18:38PM +0000, Yafang Shao wrote: > Introduce new helper get_obj_cgroup_from_cgroup() to get obj_cgroup from > a specific cgroup. > > Signed-off-by: Yafang Shao > --- > include/linux/memcontrol.h | 1 + > mm/memcontrol.c | 41 +++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 42 insertions(+) > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index 2f0a611..901a921 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -1713,6 +1713,7 @@ static inline void set_shrinker_bit(struct mem_cgroup *memcg, > int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order); > void __memcg_kmem_uncharge_page(struct page *page, int order); > > +struct obj_cgroup *get_obj_cgroup_from_cgroup(struct cgroup *cgrp); > struct obj_cgroup *get_obj_cgroup_from_current(void); > struct obj_cgroup *get_obj_cgroup_from_page(struct page *page); > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 618c366..762cffa 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2908,6 +2908,47 @@ static struct obj_cgroup *__get_obj_cgroup_from_memcg(struct mem_cgroup *memcg) > return objcg; > } > > +static struct obj_cgroup *get_obj_cgroup_from_memcg(struct mem_cgroup *memcg) > +{ > + struct obj_cgroup *objcg; > + > + if (memcg_kmem_bypass()) > + return NULL; > + > + rcu_read_lock(); > + objcg = __get_obj_cgroup_from_memcg(memcg); > + rcu_read_unlock(); > + return objcg; This code doesn't make sense to me. What does rcu read lock protect here?