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[213.151.95.130]) by smtp.gmail.com with ESMTPSA id z11sm4243298wmd.47.2020.03.10.07.32.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Mar 2020 07:32:41 -0700 (PDT) Date: Tue, 10 Mar 2020 15:32:40 +0100 From: Michal Hocko To: Baoquan He Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, x86@kernel.org Subject: Re: [PATCH] x86/mm: Remove the redundant conditional check Message-ID: <20200310143240.GL8447@dhcp22.suse.cz> References: <20200308013511.12792-1-bhe@redhat.com> <20200310101044.GE8447@dhcp22.suse.cz> <20200310142341.GG27711@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200310142341.GG27711@MiWiFi-R3L-srv> 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: On Tue 10-03-20 22:23:41, Baoquan He wrote: > On 03/10/20 at 11:10am, Michal Hocko wrote: > > On Sun 08-03-20 09:35:11, Baoquan He wrote: > > > In commit f70029bbaacbfa8f0 ("mm, memory_hotplug: drop CONFIG_MOVABLE_NODE"), > > > the dependency on CONFIG_MOVABLE_NODE was removed for N_MEMORY, so the > > > conditional check in paging_init() doesn't make any sense any more. > > > Remove it. > > > > Please expand more. I would really have to refresh the intention of the > > code but from a quick look at the code CONFIG_HIGHMEM still makes > > N_MEMORY != N_NORMAL_MEMORY. So what what does this change mean for that > > config? > > Thanks for looking into this. I was trying to explain that > CONFIG_MOVABLE_NODE made N_MEMORY have chance to take different enum > value. > > Do you think the below saying is OK to you? > > ~~~ > In commit f70029bbaacb ("mm, memory_hotplug: drop CONFIG_MOVABLE_NODE"), > the dependency on CONFIG_MOVABLE_NODE was removed for N_MEMORY. Before > commit f70029bbaacb, CONFIG_HIGHMEM && !CONFIG_MOVABLE_NODE could make > (N_MEMORY == N_NORMAL_MEMORY) be true. After commit f70029bbaacb, N_MEMORY > doesn't have any chance to be equal to N_NORMAL_MEMORY. So the conditional > check in paging_init() doesn't make any sense any more. Let's remove it. Yes this describes the matter much better. I have obviously misread the code when looking at it this morning. Being explicit in the changelog would have helped at least me. Thanks! -- Michal Hocko SUSE Labs