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Fri, 02 Apr 2021 09:21:50 -0700 (PDT) Received: from localhost ([2620:10d:c091:480::1:8ca7]) by smtp.gmail.com with ESMTPSA id j15sm7284831qtr.34.2021.04.02.09.21.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 Apr 2021 09:21:49 -0700 (PDT) Date: Fri, 2 Apr 2021 12:21:48 -0400 From: Johannes Weiner To: Muchun Song Cc: guro@fb.com, mhocko@kernel.org, akpm@linux-foundation.org, shakeelb@google.com, vdavydov.dev@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, duanxiongchun@bytedance.com, Hugh Dickins Subject: Re: [RFC PATCH 04/15] mm: memcontrol: use lruvec_memcg in lruvec_holds_page_lru_lock Message-ID: References: <20210330101531.82752-1-songmuchun@bytedance.com> <20210330101531.82752-5-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210330101531.82752-5-songmuchun@bytedance.com> X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: AEAA440002C8 X-Stat-Signature: ad9xori3j7jbadb91rry1kem636x4i1r Received-SPF: none (cmpxchg.org>: No applicable sender policy available) receiver=imf26; identity=mailfrom; envelope-from=""; helo=mail-qt1-f172.google.com; client-ip=209.85.160.172 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617380509-119183 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 Tue, Mar 30, 2021 at 06:15:20PM +0800, Muchun Song wrote: > We already have a helper lruvec_memcg() to get the memcg from lruvec, we > do not need to do it ourselves in the lruvec_holds_page_lru_lock(). So use > lruvec_memcg() instead. > > Signed-off-by: Muchun Song > --- > include/linux/memcontrol.h | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index a35a22994cf7..6e3283828391 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -744,20 +744,20 @@ static inline struct lruvec *mem_cgroup_page_lruvec(struct page *page) > return mem_cgroup_lruvec(memcg, pgdat); > } > > +static inline struct mem_cgroup *lruvec_memcg(struct lruvec *lruvec); Please reorder the functions instead to avoid forward decls. > static inline bool lruvec_holds_page_lru_lock(struct page *page, > struct lruvec *lruvec) > { > pg_data_t *pgdat = page_pgdat(page); > const struct mem_cgroup *memcg; > - struct mem_cgroup_per_node *mz; > > if (mem_cgroup_disabled()) > return lruvec == &pgdat->__lruvec; > > - mz = container_of(lruvec, struct mem_cgroup_per_node, lruvec); > memcg = page_memcg(page) ? : root_mem_cgroup; > > - return lruvec->pgdat == pgdat && mz->memcg == memcg; > + return lruvec->pgdat == pgdat && lruvec_memcg(lruvec) == memcg; Looks reasonable to me, but I wonder if there is more we can do. lruvec_memcg() already handles CONFIG_MEMCG and mem_cgroup_disabled() combinations, and there is also a lruvec_pgdat() which does. One thing that is odd is page_memcg(page) ? : root_mem_cgroup. How can lruvec pages not have a page_memcg()? mem_cgroup_page_lruvec() has: memcg = page_memcg(page); VM_WARN_ON_ONCE_PAGE(!memcg && !mem_cgroup_disabled(), page); Unless I'm missing something, we should be able to have a single definition for this function that works for !CONFIG_MEMCG, CONFIG_MEMCG + mem_cgroup_disabled() and CONFIG_MEMCG: lruvec_holds_page_lru_lock() { return lruvec_pgdat(lruvec) == page_pgdat(page) && lruvec_memcg(lruvec) == page_memcg(page); }