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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1761660225; 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=F4kFK5BJ7jqgsuSDiSoEfAf9VHgtSpfSrzUfS3UnF3Y=; b=MfRN3t19XYpdxb4wcQVFPd3/mu0+cZ9GQ7ccvIU9cBaG4F2YOqrqyvYKeVRMsZKhWRNqj7 eZDaToOPOy6Fi94Ky9Hi3X1Abh0FGtpGNvKor+IdkbwbYytdVygxKfFANTcCJ8v46nZnuG nroMiEABUxj0K9UP7lCdMidgPxFPqE0= 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@redhat.com, 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, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng Subject: [PATCH v1 14/26] mm: memcontrol: prevent memory cgroup release in mem_cgroup_swap_full() Date: Tue, 28 Oct 2025 21:58:27 +0800 Message-ID: <1593e9efc2de666e9f7e7659d5c61d2ccdd17a8d.1761658310.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: rspam05 X-Stat-Signature: pxnmu3oof84newb3qzr5me3zqk6wnckd X-Rspam-User: X-Rspamd-Queue-Id: 19E75140023 X-HE-Tag: 1761660226-329781 X-HE-Meta: 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 Xsjkl6jI ibACFAEABexaWiQ0SUCkedcvgd1VWLjy8OEXLbYCTf8DDVe3i3Fe8+SqlUUIBmJ7kzL+tXlh8YE89aTDaoOazlRK2n8W1Ig4BYPtavCrbkCyjeoNhVzzjXMAF6OQZggDVkYKJ17HE1FpG3nKnmdhPKE+k2spmWmTkbsZHTwkznpPbdBbTI7VWVRSkAFtUsDmD3YbWuPrR9BpVZO8rHbum8nmInZY1vDE6GtkJeGqWbg8Q7jrgxkLYfeSQSWlQYw3IS4BuBc1ShkK1CxY= 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: 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 --- mm/memcontrol.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index aa8945c4ee383..4b3c7d4f346b5 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5275,17 +5275,21 @@ bool mem_cgroup_swap_full(struct folio *folio) if (do_memsw_account()) return false; - memcg = folio_memcg(folio); - if (!memcg) + if (!folio_memcg_charged(folio)) return false; + rcu_read_lock(); + memcg = folio_memcg(folio); 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)) + usage * 2 >= READ_ONCE(memcg->swap.max)) { + rcu_read_unlock(); return true; + } } + rcu_read_unlock(); return false; } -- 2.20.1