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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: Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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?