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[109.81.81.105]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4318b55f50csm11444305e9.17.2024.10.24.02.16.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Oct 2024 02:16:53 -0700 (PDT) Date: Thu, 24 Oct 2024 11:16:52 +0200 From: Michal Hocko To: Shakeel Butt Cc: Andrew Morton , Johannes Weiner , Roman Gushchin , Muchun Song , Hugh Dickins , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, Meta kernel team Subject: Re: [RFC PATCH 3/3] memcg-v1: remove memcg move locking code Message-ID: References: <20241024065712.1274481-1-shakeel.butt@linux.dev> <20241024065712.1274481-4-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241024065712.1274481-4-shakeel.butt@linux.dev> X-Rspam-User: X-Rspamd-Queue-Id: F0CFA80010 X-Rspamd-Server: rspam01 X-Stat-Signature: fuezq11bxfymtp5dz9x3rqo17jx6c4sn X-HE-Tag: 1729761380-821658 X-HE-Meta: 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 6kKkTIRx a7vtEfHWamsUYMFclWlrZrJIlolcRgQ8/FaAs48NskTyTii5kCtYT/v5YFvohEmUYeNSCmpZEQ4RH3lbBqjIsYv2kjdjdAeOMo4c84XBHxTO4ciV5UhEgApPf7xa8vDztrFkxwogI+RnNfwweTSLAwb8mAqo89C+olrl98ZCC+zSpdKY1S0k1Tpzx/APpqvZVL5Ah034p3tQndoB3gUZJ9ZiiXPBfJnhfeDCUZH6rkNPuyF5RuYayb7KEWvzWkAJ3ScHHcNpmbuGSL/sCejxs4cS8ldTACiyVwP/JUJ0zE3o2WMsK1VLcTPnlag== 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 Wed 23-10-24 23:57:12, Shakeel Butt wrote: > The memcg v1's charge move feature has been deprecated. There is no need > to have any locking or protection against the moving charge. Let's > proceed to remove all the locking code related to charge moving. > > Signed-off-by: Shakeel Butt > --- > -/** > - * folio_memcg_lock - Bind a folio to its memcg. > - * @folio: The folio. > - * > - * This function prevents unlocked LRU folios from being moved to > - * another cgroup. > - * > - * It ensures lifetime of the bound memcg. The caller is responsible > - * for the lifetime of the folio. > - */ > -void folio_memcg_lock(struct folio *folio) > -{ > - struct mem_cgroup *memcg; > - unsigned long flags; > - > - /* > - * The RCU lock is held throughout the transaction. The fast > - * path can get away without acquiring the memcg->move_lock > - * because page moving starts with an RCU grace period. > - */ > - rcu_read_lock(); Is it safe to remove the implicit RCU? -- Michal Hocko SUSE Labs