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[134.134.136.20]) by mx.google.com with ESMTPS id x123si2351180pfx.157.2019.05.06.10.57.29 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 06 May 2019 10:57:30 -0700 (PDT) Received-SPF: pass (google.com: domain of dave.hansen@intel.com designates 134.134.136.20 as permitted sender) client-ip=134.134.136.20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of dave.hansen@intel.com designates 134.134.136.20 as permitted sender) smtp.mailfrom=dave.hansen@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 06 May 2019 10:57:29 -0700 X-ExtLoop1: 1 Received: from ray.jf.intel.com (HELO [10.7.201.126]) ([10.7.201.126]) by orsmga002.jf.intel.com with ESMTP; 06 May 2019 10:57:29 -0700 Subject: Re: [v5 2/3] mm/hotplug: make remove_memory() interface useable To: Pavel Tatashin , jmorris@namei.org, sashal@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@lists.01.org, akpm@linux-foundation.org, mhocko@suse.com, dave.hansen@linux.intel.com, dan.j.williams@intel.com, keith.busch@intel.com, vishal.l.verma@intel.com, dave.jiang@intel.com, zwisler@kernel.org, thomas.lendacky@amd.com, ying.huang@intel.com, fengguang.wu@intel.com, bp@suse.de, bhelgaas@google.com, baiyaowei@cmss.chinamobile.com, tiwai@suse.de, jglisse@redhat.com, david@redhat.com References: <20190502184337.20538-1-pasha.tatashin@soleen.com> <20190502184337.20538-3-pasha.tatashin@soleen.com> From: Dave Hansen Openpgp: preference=signencrypt Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190502184337.20538-3-pasha.tatashin@soleen.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit 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: > -static inline void remove_memory(int nid, u64 start, u64 size) {} > +static inline bool remove_memory(int nid, u64 start, u64 size) > +{ > + return -EBUSY; > +} This seems like an appropriate place for a WARN_ONCE(), if someone manages to call remove_memory() with hotplug disabled. BTW, I looked and can't think of a better errno, but -EBUSY probably isn't the best error code, right? > -void remove_memory(int nid, u64 start, u64 size) > +/** > + * remove_memory > + * @nid: the node ID > + * @start: physical address of the region to remove > + * @size: size of the region to remove > + * > + * NOTE: The caller must call lock_device_hotplug() to serialize hotplug > + * and online/offline operations before this call, as required by > + * try_offline_node(). > + */ > +void __remove_memory(int nid, u64 start, u64 size) > { > + > + /* > + * trigger BUG() is some memory is not offlined prior to calling this > + * function > + */ > + if (try_remove_memory(nid, start, size)) > + BUG(); > +} Could we call this remove_offline_memory()? That way, it makes _some_ sense why we would BUG() if the memory isn't offline.