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Tue, 6 Sep 2022 00:49:25 +0000 Received: from BY5PR12MB4130.namprd12.prod.outlook.com ([fe80::508d:221c:9c9e:e1a5]) by BY5PR12MB4130.namprd12.prod.outlook.com ([fe80::508d:221c:9c9e:e1a5%9]) with mapi id 15.20.5588.018; Tue, 6 Sep 2022 00:49:25 +0000 Message-ID: <1c05b986-e8bb-2ec1-7c81-06b7cfe50f94@nvidia.com> Date: Mon, 5 Sep 2022 17:49:23 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.0 Subject: Re: [PATCH] mm: Check writable zero page in page table check Content-Language: en-US To: "Huang, Shaoqin" , "Edgecombe, Rick P" , "akpm@linux-foundation.org" , "linux-mm@kvack.org" , "pasha.tatashin@soleen.com" Cc: "linux-kernel@vger.kernel.org" References: <20220902232732.12358-1-rick.p.edgecombe@intel.com> <3d82deb6-357d-0b54-ffd1-dce157674aad@intel.com> <467b0cdb4f876b87b50d1cd7229a8e6e02a19a41.camel@intel.com> <4f265843-bac1-944c-8119-aa4c1689c8e5@intel.com> From: John Hubbard In-Reply-To: <4f265843-bac1-944c-8119-aa4c1689c8e5@intel.com> Content-Type: text/plain; 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imf26.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=a0EK+o4Z; spf=pass (imf26.hostedemail.com: domain of jhubbard@nvidia.com designates 40.107.92.48 as permitted sender) smtp.mailfrom=jhubbard@nvidia.com; arc=pass ("microsoft.com:s=arcselector9901:i=1"); dmarc=pass (policy=reject) header.from=nvidia.com ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1662425367; a=rsa-sha256; cv=pass; b=oQZ4wNWp3B753HuWVJR/Bh5pSwa/bikcQfnYkjKgrNVbi6bmfhKva+8e/jHVyRaxzkLw9b Oce16NR8vrAZy2Ew4ltH2X4uWQixSbphlPRlHoG9lhP5Fjcg+awXBk10DnQOm7Bp8vweXt QlLrbvObnO1vcvOoXwFkULXiQND7vYw= ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1662425367; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=fKVfSkFX5NhOFhDWiNT3bE43fIRQ0ejrk3UyOWIqSMY=; b=kWnt+1UA1hXUrmpyxJv0SPg5qKR53t/5T4xZUT7Bg255lJwtVa/tSlirBoKOMrQkS33oVD ibbVns+n/nnkNpnk/sBSHF8i+jkRCUhMRrWYU6NtuOTDML2pn+J6Ggjxfpz8IeXyXBfw5l SY8oAuT7JXnnoy2MdbpnzjgzrByZUm8= Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=a0EK+o4Z; spf=pass (imf26.hostedemail.com: domain of jhubbard@nvidia.com designates 40.107.92.48 as permitted sender) smtp.mailfrom=jhubbard@nvidia.com; arc=pass ("microsoft.com:s=arcselector9901:i=1"); dmarc=pass (policy=reject) header.from=nvidia.com X-Rspam-User: X-Stat-Signature: 17t5eq8bmunwqaiy9kp48nzpmaksexax X-Rspamd-Queue-Id: 5DAC2140089 X-Rspamd-Server: rspam05 X-HE-Tag: 1662425367-947069 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 9/5/22 17:24, Huang, Shaoqin wrote: > > > On 9/6/2022 2:50 AM, Edgecombe, Rick P wrote: >> On Sat, 2022-09-03 at 10:13 +0800, Huang, Shaoqin wrote: >>>> + BUG_ON(is_zero_pfn(pfn) && rw); >>>> + >>> >>> Why we need use BUG_ON() here? Based on [1], we should avoid to use >>> the >>> BUG_ON() due to it will panic the machine. >>> >>> [1]: >>> https://lore.kernel.org/lkml/20220824163100.224449-1-david@redhat.com/ >> >> Yea, you are probably right. All the rest of this checker uses BUG_ON() >> though. Maybe they should all be something else? Just felt weird to >> have this be the only check that is different. >> >> I don't have any objections to changing it to WARN_ON(). Should I >> switch the rest of the checks here while I'm at it? > > Yes. I think in most situation, WARN_ON() or WARN_ON_ONCE() is ok. > +1 for WARN_ON_ONCE(), and also for changing the other cases as you find them, yes. thanks, -- John Hubbard NVIDIA