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[195.135.220.15]) by mx.google.com with ESMTPS id r5si2598237ejj.371.2019.07.01.03.47.00 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 01 Jul 2019 03:47:00 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 972EBAD8D; Mon, 1 Jul 2019 10:46:59 +0000 (UTC) Date: Mon, 1 Jul 2019 12:46:58 +0200 From: Michal Hocko To: Alastair D'Silva Cc: Greg Kroah-Hartman , "Rafael J. Wysocki" , Andrew Morton , Pavel Tatashin , Oscar Salvador , Mike Rapoport , Baoquan He , Wei Yang , Logan Gunthorpe , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 1/3] mm: Trigger bug on if a section is not found in __section_nr Message-ID: <20190701104658.GA6549@dhcp22.suse.cz> References: <20190626061124.16013-1-alastair@au1.ibm.com> <20190626061124.16013-2-alastair@au1.ibm.com> <20190626062113.GF17798@dhcp22.suse.cz> <20190626065751.GK17798@dhcp22.suse.cz> <20190627080724.GK17798@dhcp22.suse.cz> <833b9675bc363342827cb8f7c76ebb911f7f960d.camel@d-silva.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <833b9675bc363342827cb8f7c76ebb911f7f960d.camel@d-silva.org> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Fri 28-06-19 10:46:28, Alastair D'Silva wrote: [...] > Given that there is already a VM_BUG_ON in the code, how do you feel > about broadening the scope from 'VM_BUG_ON(!root)' to 'VM_BUG_ON(!root > || (root_nr == NR_SECTION_ROOTS))'? As far as I understand the existing VM_BUG_ON will hit when the mem_section tree gets corrupted. This is a different situation to an incorrect section given so I wouldn't really mix those two. And I still do not see much point to protect from unexpected input parameter as this is internal function as already pointed out. -- Michal Hocko SUSE Labs