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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1772006037; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=evy5ffpxH1pOU6KU8S5DoExZmuc8IAjbV0oiS0M36hM=; b=g3rebzToh1hmOrEwT2+sdp8wYVlVus/EBrCeGuyjsCEjNs2drr/ZTMn+w+VAhfz2d3tNLr ifGKzr05BrM3HBVGfTC7WwluBv7BEAvXdSTvJm6omLOYrY6tWtzSgHO7lXA76lsN0OLqES XeLwZRjbQWqzjmA+WJTH0BOTXf4hl68= From: Qi Zheng To: hannes@cmpxchg.org, 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, yosry.ahmed@linux.dev, 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, bhe@redhat.com, usamaarif642@gmail.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng Subject: [PATCH v5 15/32] mm: memcontrol: prevent memory cgroup release in mem_cgroup_swap_full() Date: Wed, 25 Feb 2026 15:52:58 +0800 Message-ID: <21d1abab7342615745ea4c18a88237335ab44d13.1772005110.git.zhengqi.arch@bytedance.com> In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam09 X-Stat-Signature: qnq3rzuekq4tnkzze318poahhib9ywap X-Rspamd-Queue-Id: 28D51C000B X-Rspam-User: X-HE-Tag: 1772006038-47662 X-HE-Meta: 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 dS8AC0Bh iXiLapZ4CNKZEZWhC1ch+cVkcFohOkhMg0E/I9RmG1sGl32C1H/zeiSWr5a5lz0lL1+FMxqnc9TbHslNz64Vqmzr0U1S58s4I448EnqVRn3JEJvGMR827Aoe9kfIZiovbyna4BDhSzvTGUiVSpbbzHYSUPMBzVApL6NOdyvjqsrJTI4rvuFXXyINm4DD+xzlynXUZTCE1bOZBAWjpvwyCk8ufpvruMShCCw0vaWmkWlxzNNHgMWlr9GcpYlOTDx0qHI2d73uvITeMZd65KjEXu9jo1jGiu6jL6lMDFj0vQbZhUZRna1yOvQW5z3ik+YXh7PSV Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Muchun Song In the near future, a folio will no longer pin its corresponding memory cgroup. To ensure safety, it will only be appropriate to hold the rcu read lock or acquire a reference to the memory cgroup returned by folio_memcg(), thereby preventing it from being released. In the current patch, the rcu read lock is employed to safeguard against the release of the memory cgroup in mem_cgroup_swap_full(). This serves as a preparatory measure for the reparenting of the LRU pages. Signed-off-by: Muchun Song Signed-off-by: Qi Zheng Reviewed-by: Harry Yoo Acked-by: Johannes Weiner Acked-by: Shakeel Butt --- mm/memcontrol.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index a4bb8b8b2c457..063fdfdd58223 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5345,27 +5345,29 @@ long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg) bool mem_cgroup_swap_full(struct folio *folio) { struct mem_cgroup *memcg; + bool ret = false; VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); if (vm_swap_full()) return true; - if (do_memsw_account()) - return false; + if (do_memsw_account() || !folio_memcg_charged(folio)) + return ret; + rcu_read_lock(); memcg = folio_memcg(folio); - if (!memcg) - return false; - for (; !mem_cgroup_is_root(memcg); memcg = parent_mem_cgroup(memcg)) { unsigned long usage = page_counter_read(&memcg->swap); if (usage * 2 >= READ_ONCE(memcg->swap.high) || - usage * 2 >= READ_ONCE(memcg->swap.max)) - return true; + usage * 2 >= READ_ONCE(memcg->swap.max)) { + ret = true; + break; + } } + rcu_read_unlock(); - return false; + return ret; } static int __init setup_swap_account(char *s) -- 2.20.1