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[109.81.81.105]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43186bd6923sm40205915e9.9.2024.10.24.02.14.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Oct 2024 02:14:02 -0700 (PDT) Date: Thu, 24 Oct 2024 11:14:01 +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 1/3] memcg-v1: fully deprecate move_charge_at_immigrate Message-ID: References: <20241024065712.1274481-1-shakeel.butt@linux.dev> <20241024065712.1274481-2-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241024065712.1274481-2-shakeel.butt@linux.dev> X-Rspamd-Queue-Id: 306EC8000C X-Stat-Signature: z4yhaw5nwmc18fdqre1wykzp4miw1m1b X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1729761208-660587 X-HE-Meta: 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 a1IodDdg LhBEHPKxBRdiFQYgWUn3LczBvdvJwX0rL/RkHZIO+vsblztCtdIe3nFcSuyHYNs6mVGF15VxQ5SRnfp+ZwXUV+S6sy+k2p3BRe3521O5R2TgbZ23UW2IGhhR4xClW3mxLCEzqlKeih6zu778z6uDYqy8qYSIl+Nw0sbRlsUR6q610d6/6sWPw5edgtgsC75xaC5o5saDAMDSDvi0/8tK1r3WN1ZKSfriKIXWfGFpKgYPag3WXk5RfaNcvwoPOhX9Bgn1toKB9otLNvTGi0obqp2v8oTYCXpWqugHDheBhg4JFXQtrk9/uG1MZgpk7XZqaJVZm+8XWpyAg/b/5etBPyiLhxFY8QmE06GN11k/9bN6sGq60OKuatxxsBHfjJySb5il7iqOMMoIZ4COXbA+489jlNQwAdKT4qEmE 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 23:57:10, Shakeel Butt wrote: > Proceed with the complete deprecation of memcg v1's charge moving > feature. The deprecation warning has been in the kernel for almost two > years and has been ported to all stable kernel since. Now is the time to > fully deprecate this feature. > > Signed-off-by: Shakeel Butt I fine with this move, just one detail we might need to consider [...] > @@ -606,17 +606,7 @@ static int mem_cgroup_move_charge_write(struct cgroup_subsys_state *css, > "Please report your usecase to linux-mm@kvack.org if you " > "depend on this functionality.\n"); > > - if (val & ~MOVE_MASK) > - return -EINVAL; > - > - /* > - * No kind of locking is needed in here, because ->can_attach() will > - * check this value once in the beginning of the process, and then carry > - * on with stale data. This means that changes to this value will only > - * affect task migrations starting after the change. > - */ > - memcg->move_charge_at_immigrate = val; > - return 0; > + return -EINVAL; Would it make more sense to -EINVAL only if val != 0? The reason being that some userspace might be just writing 0 here for whatever reason and see the failure unexpected. > } > #else > static int mem_cgroup_move_charge_write(struct cgroup_subsys_state *css, > -- > 2.43.5 -- Michal Hocko SUSE Labs