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Thu, 09 Jan 2020 23:00:21 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.27/8.16.0.27) with SMTP id 009MxV2G054635; Thu, 9 Jan 2020 23:00:21 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserp3030.oracle.com with ESMTP id 2xdj4rnv9w-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 09 Jan 2020 23:00:21 +0000 Received: from abhmp0012.oracle.com (abhmp0012.oracle.com [141.146.116.18]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 009N0JoQ011299; Thu, 9 Jan 2020 23:00:20 GMT Received: from [192.168.1.206] (/71.63.128.209) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 09 Jan 2020 15:00:19 -0800 Subject: Re: [PATCH v2] mm/page_vma_mapped.c: Detect mismatched pfn of hugetlbfs page in pfn_in_hpage() To: Li Xinhai , Michal Hocko Cc: "linux-mm@kvack.org" , "kirill.shutemov" References: <1578579963-6075-1-git-send-email-lixinhai.lxh@gmail.com> <20200109150052.GT4951@dhcp22.suse.cz> <568a2f44-ad16-f3b5-4691-4e6f6ff21bf1@oracle.com> <2020011006480540632892@gmail.com> From: Mike Kravetz Message-ID: Date: Thu, 9 Jan 2020 15:00:18 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <2020011006480540632892@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9495 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-2001090192 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9495 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-2001090192 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 1/9/20 2:48 PM, Li Xinhai wrote: > oops, I didn't write the code correctly. I should wrote it as > > if (pfn >= hpage_pfn && pfn - hpage_pfn < hpage_nr_pages(hpage)) { > VM_BUG_ON_PAGE(PageHuge(hpage) && pfn != hpage_pfn, hpage); > return true; > } > > return false; > > hpage_nr_pages(hpage) give us HPAGE_PMD_NR for THP and hugetlbfs page, > but remapping PTE to a differrnt hugetlbfs page still allowed, so put the BUG code > into this condition is necessary. By this way, if it was not a exact match for PageHuge, > then it is a bug. Thank you. I think we all agree on what the proposed code is doing. However, we would like to know why you believe this code should be added. For example, - Did you actually encounter this situation (PageHuge(hpage) && pfn != hpage_pfn)? - Did you discover some code path where we are likely to encounter this situation? - Some other reason? -- Mike Kravetz