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Thu, 25 Sep 2025 10:07:47 -0700 (PDT) Message-ID: <01e7eccd-3529-4d12-8ad2-fd9e034a026d@yukuai.org.cn> Date: Fri, 26 Sep 2025 01:07:39 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 01/10] blk-cgroup: use cgroup lock and rcu to protect iterating blkcg blkgs To: Bart Van Assche , Yu Kuai , tj@kernel.org, ming.lei@redhat.com, nilay@linux.ibm.com, hch@lst.de, josef@toxicpanda.com, axboe@kernel.dk, akpm@linux-foundation.org, vgoyal@redhat.com Cc: cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, yukuai3@huawei.com, yi.zhang@huawei.com, yangerkun@huawei.com, johnny.chenyi@huawei.com References: <20250925081525.700639-1-yukuai1@huaweicloud.com> <20250925081525.700639-2-yukuai1@huaweicloud.com> From: Yu Kuai In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-ZohoMailClient: External X-Rspamd-Queue-Id: 0F00C160015 X-Stat-Signature: 731yipococ44qh1gq8marcrkarwh7ytc X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1758820090-454823 X-HE-Meta: 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 nYJKZdSz a7cLOwoeX6yLsBIQvUMTcIbvHeAg9/FzbpeQCcvhHsnDfohQ9pVfz7gx9seBPTYQNzjjB7zf9I/OLXqieh/zO1QhV/lNawfkNwnkkh8i+7KDLn27lHJzH5LYWq7i/evqPo0LWRlz/t1M6VPlgwZGYm5OhbszTFqP0zeYe6Yzfwx9biV7hO0K6Dy7FUheBy/3cRsI0zmssb2Qpbbkhpr+Yab7HC093jFxqD36h8ng8RDBCDtbL2ADnybi5asE2lIz3hrwNSvlGjaOcWE8mhjbLRMJ4ltAwKa50bExXqW6fXqfgDF/fFseCGVN7dOxdXs1BIwH+B/bDBpcX9lfxRXCq+AcSU6PVNjHihy+Lwrgu5AVLNaXx4PGR8ApsMsykMQW88cVLVu1Uk3ei5A3dbEq0gSp1BlCCDJXDd6bl2FzdJgbhpOPtUuzMOJ+SXILs0ucYtysimOw2hHmBKCVU06wUU5wt3w== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi, 在 2025/9/25 23:57, Bart Van Assche 写道: > On 9/25/25 1:15 AM, Yu Kuai wrote: >> It's safe to iterate blkgs with cgroup lock or rcu lock held, prevent >> nested queue_lock under rcu lock, and prepare to convert protecting >> blkcg with blkcg_mutex instead of queuelock. > > Iterating blkgs without holding q->queue_lock is safe but accessing the > blkg members without holding that lock is not safe since q->queue_lock > is acquired by all code that modifies blkg members. Should perhaps a new > spinlock be introduced to serialize blkg modifications? > No need for a new lock, I think blkcg->lock can do that. Thanks, Kuai > Thanks, > > Bart. >