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c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1766716164; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=EglM8RmrzRaeH2nN610Fc9DffZwAgKEyt3X5gxV+fUU=; b=N8RY20tuSV3V106VEewEiHoviQyufCudiFHnxN4dHfmA1JZjYH2QP0apvtiNpWoUn8lQaI gX5n/8ZRdS2MDeySeLH4uQzoxK6jKKSRNe8c0A4A5dWOd90ZnRkmt0kZeggd5fo2B1DL9/ HG6nOFWVABpEaFOlSYpt9Ku3Rhz0krE= Received: from mail.maildlp.com (unknown [172.19.163.198]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTPS id 4dcqLF4YZqzKHMTQ for ; Fri, 26 Dec 2025 10:28:53 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.128]) by mail.maildlp.com (Postfix) with ESMTP id D3CA040574 for ; Fri, 26 Dec 2025 10:29:15 +0800 (CST) Received: from [10.67.111.176] (unknown [10.67.111.176]) by APP4 (Coremail) with SMTP id gCh0CgAXefn68k1pwXQEBg--.55072S2; Fri, 26 Dec 2025 10:29:15 +0800 (CST) Message-ID: <76e134d7-19ae-43dd-abb8-6ce8ba24670c@huaweicloud.com> Date: Fri, 26 Dec 2025 10:29:14 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 15/28] mm: memcontrol: prevent memory cgroup release in mem_cgroup_swap_full() To: Shakeel Butt , Qi Zheng Cc: hannes@cmpxchg.org, hughd@google.com, mhocko@suse.com, roman.gushchin@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, 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 References: <4dd1fb48ef4367e0932dbe7265d876bd95880808.1765956025.git.zhengqi.arch@bytedance.com> Content-Language: en-US From: Chen Ridong In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CM-TRANSID:gCh0CgAXefn68k1pwXQEBg--.55072S2 X-Coremail-Antispam: 1UD129KBjvJXoWxJw4fKr1UWr1DAr1fKryUZFb_yoW5Xr1rpF Z5Kas8AF48Aw4xur1aq3Wj9ryFy3yIqws8tFWxKw1fA3W3Xwn8CrW7Kw1UXa45AF1xuFyx XF1jv3W7uayjya7anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvYb4IE77IF4wAFF20E14v26ryj6rWUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x 0267AKxVW0oVCq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG 6I80ewAv7VC0I7IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFV Cjc4AY6r1j6r4UM4x0Y48IcVAKI48JM4IIrI8v6xkF7I0E8cxan2IY04v7MxkF7I0En4kS 14v26r4a6rW5MxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I0E5I 8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVW8ZVWr XwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x 0267AKxVW8JVWxJwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI0_ Jr0_Gr1lIxAIcVC2z280aVCY1x0267AKxVW8Jr0_Cr1UYxBIdaVFxhVjvjDU0xZFpf9x07 jIksgUUUUU= X-CM-SenderInfo: hfkh02xlgr0w46kxt4xhlfz01xgou0bp/ X-Rspamd-Queue-Id: 6FA8B140008 X-Stat-Signature: 1gwj6ktu9r4np7jcrcxa1s7r7a59qbes X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1766716160-843832 X-HE-Meta: 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 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 2025/12/20 9:05, Shakeel Butt wrote: > On Wed, Dec 17, 2025 at 03:27:39PM +0800, Qi Zheng wrote: >> 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 >> --- >> mm/memcontrol.c | 10 +++++++--- >> 1 file changed, 7 insertions(+), 3 deletions(-) >> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >> index 131f940c03fa0..f2c891c1f49d5 100644 >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -5267,17 +5267,21 @@ 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; >> } > > How about the following? > > > 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 (!folio_memcg_charged(folio)) > - return false; > + if (do_memsw_account() || !folio_memcg_charged(folio)) > + return ret; > > rcu_read_lock(); > memcg = folio_memcg(folio); > @@ -5277,13 +5276,13 @@ bool mem_cgroup_swap_full(struct folio *folio) > > if (usage * 2 >= READ_ONCE(memcg->swap.high) || > usage * 2 >= READ_ONCE(memcg->swap.max)) { > - rcu_read_unlock(); > - return true; > + ret = true; > + break; > } > } > rcu_read_unlock(); > > - return false; > + return ret; > } > > > Anyways LGTM. > > Acked-by: Shakeel Butt More compact. LGTM. -- Best regards, Ridong