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Wed, 17 Dec 2025 14:18:41 -0800 (PST) Date: Wed, 17 Dec 2025 17:18:40 -0500 From: Johannes Weiner To: Qi Zheng Cc: hughd@google.com, mhocko@suse.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, david@kernel.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, harry.yoo@oracle.com, imran.f.khan@oracle.com, kamalesh.babulal@oracle.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, chenridong@huaweicloud.com, mkoutny@suse.com, akpm@linux-foundation.org, hamzamahfooz@linux.microsoft.com, apais@linux.microsoft.com, lance.yang@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng Subject: Re: [PATCH v2 14/28] mm: mglru: prevent memory cgroup release in mglru Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: s9iqy63x5kzhiyqxyht4385km6foj8zm X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 083C240008 X-Rspam-User: X-HE-Tag: 1766009922-950668 X-HE-Meta: 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 nK7SO3i/ 6aAM4vvT77fwdIPZWMvlpeRY1h1EUem2Kw/cFhW3oeV7ZXLgGIWhQ5NZHRYYD484KkoOxwbybt5PpYv6dsgOgQgLKvAxOl2B/WcbGaq6ZFXCKW8tdmaymA08QZ2VP4KPCslFyNOoyWqb6P5w/f1WW1fiFkm8Ta/pu8Z5LhHgMoRueGn8CMUEmrgQq0Jh4bu69evbMJ0GlVt73M8MLCtaegwwtRxLtG02kGyb0lO+IzO0S9pAzXPU17liYvWTC5tzTY15UwRfMHx/Jz2zEF36z22pbMIHmnqXlbz9KHlXwJZwkrwKcb0f+Zq66KnHkN4eygKd5sUz0KEFLw5AjngD8AGTTM3z2BeWVR+/Unj0lyXJ2ISCzTT/5a6Mnx1CJVhe39SZ3Ruv2FJDj+61BL7xxGWyDpA== 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: List-Subscribe: List-Unsubscribe: On Wed, Dec 17, 2025 at 03:27:38PM +0800, Qi Zheng wrote: > @@ -4242,6 +4244,13 @@ bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw) > } > } > > + rcu_read_lock(); > + memcg = folio_memcg(folio); > + lruvec = mem_cgroup_lruvec(memcg, pgdat); > + max_seq = READ_ONCE((lruvec)->lrugen.max_seq); > + gen = lru_gen_from_seq(max_seq); > + mm_state = get_mm_state(lruvec); > + > arch_enter_lazy_mmu_mode(); > > pte -= (addr - start) / PAGE_SIZE; > @@ -4282,6 +4291,8 @@ bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw) > if (mm_state && suitable_to_scan(i, young)) > update_bloom_filter(mm_state, max_seq, pvmw->pmd); > > + rcu_read_unlock(); > + > return true; This seems a bit long to be holding the rcu lock. Maybe do a get and a put instead?