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[156.151.31.86]) by mx.google.com with ESMTPS id b89si8472977plb.351.2019.05.10.15.45.29 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 10 May 2019 15:45:30 -0700 (PDT) Received-SPF: pass (google.com: domain of mike.kravetz@oracle.com designates 156.151.31.86 as permitted sender) client-ip=156.151.31.86; Authentication-Results: mx.google.com; dkim=pass header.i=@oracle.com header.s=corp-2018-07-02 header.b=tJDg3KFb; spf=pass (google.com: domain of mike.kravetz@oracle.com designates 156.151.31.86 as permitted sender) smtp.mailfrom=mike.kravetz@oracle.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=oracle.com Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x4AMiYvu139156; Fri, 10 May 2019 22:45:12 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2018-07-02; bh=bf8P4q788pObPSRhE2yikT3tYYSQpmCfY0xoTw+mRbc=; b=tJDg3KFbDYIWEVqN4zRx/qTj/SM3kNWXyLq8DekKk43DPTy4EJHOJoil4dQOslSkD0Fq 8iunHzoBxOxSlelf6JLFmdzQj8nXkCwduTFP+mohuZ+4V+/7WVXDuCxhJrPY1cft9uTr VA5djX2Z2BfHHiFh2M0+dgE6PGwYX3rNP04HmZlOrNHmOWNZXxfBJumAOJDD5eVF04g6 XPVd8mPBJD+Ad9RnRpO5yydcWexPYUKDqDWwZvF7uDkbGFCegZTnQpN+9FxA5Ch0syFd ikPpnIjYazDAUp4v/QAMiW7CUYHo9JQkntMVr4FFPQkiTysvRcYATetsKTdoJc9xBSWY Xg== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by userp2130.oracle.com with ESMTP id 2s94bgkuj5-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 10 May 2019 22:45:12 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x4AMhSbp190646; Fri, 10 May 2019 22:45:12 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userp3020.oracle.com with ESMTP id 2s94ahm8f7-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 10 May 2019 22:45:11 +0000 Received: from abhmp0017.oracle.com (abhmp0017.oracle.com [141.146.116.23]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x4AMj5kX031257; Fri, 10 May 2019 22:45:05 GMT Received: from [192.168.1.222] (/71.63.128.209) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Fri, 10 May 2019 15:45:05 -0700 Subject: Re: [PATCH, RFC 2/2] Implement sharing/unsharing of PMDs for FS/DAX To: Larry Bassel , Matthew Wilcox Cc: dan.j.williams@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org References: <1557417933-15701-1-git-send-email-larry.bassel@oracle.com> <1557417933-15701-3-git-send-email-larry.bassel@oracle.com> <20190509164914.GA3862@bombadil.infradead.org> <20190510161607.GB27674@ubuette> From: Mike Kravetz Message-ID: Date: Fri, 10 May 2019 15:45:04 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190510161607.GB27674@ubuette> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9253 signatures=668686 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=8.0.1-1810050000 definitions=main-1905100144 X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9253 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1905100144 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 5/10/19 9:16 AM, Larry Bassel wrote: > On 09 May 19 09:49, Matthew Wilcox wrote: >> On Thu, May 09, 2019 at 09:05:33AM -0700, Larry Bassel wrote: >>> This is based on (but somewhat different from) what hugetlbfs >>> does to share/unshare page tables. >> >> Wow, that worked out far more cleanly than I was expecting to see. > > Yes, I was pleasantly surprised. As I've mentioned already, I > think this is at least partially due to the nature of DAX. I have not looked in detail to make sure this is indeed all the places you need to hook and special case for sharing/unsharing. Since this scheme is somewhat like that used for hugetlb, I just wanted to point out some nasty bugs related to hugetlb PMD sharing that were fixed last year. 5e41540c8a0f hugetlbfs: fix kernel BUG at fs/hugetlbfs/inode.c:444! dff11abe280b hugetlb: take PMD sharing into account when flushing tlb/caches 017b1660df89 mm: migration: fix migration of huge PMD shared pages The common issue in these is that when unmapping a page with a shared PMD mapping you need to flush the entire shared range and not just the unmapped page. The above changes were hugetlb specific. I do not know if any of this applies in the case of DAX. -- Mike Kravetz