From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 56A17C432C0 for ; Thu, 28 Nov 2019 22:39:12 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E64D320880 for ; Thu, 28 Nov 2019 22:39:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="K+IKYnZ/" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E64D320880 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 4C0F86B0559; Thu, 28 Nov 2019 17:39:11 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 471016B055A; Thu, 28 Nov 2019 17:39:11 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 35F5D6B055B; Thu, 28 Nov 2019 17:39:11 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0079.hostedemail.com [216.40.44.79]) by kanga.kvack.org (Postfix) with ESMTP id 1F2696B0559 for ; Thu, 28 Nov 2019 17:39:11 -0500 (EST) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with SMTP id C01AE2C32 for ; Thu, 28 Nov 2019 22:39:10 +0000 (UTC) X-FDA: 76207153260.19.force70_6d2dead2c1b24 X-HE-Tag: force70_6d2dead2c1b24 X-Filterd-Recvd-Size: 3951 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf05.hostedemail.com (Postfix) with ESMTP for ; Thu, 28 Nov 2019 22:39:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=pZCnrPr2b9gLMJqHgJo0gt01BaizFyA66hYSt9kdrmM=; b=K+IKYnZ/GsB+ZkQTbcKnhP/Pc c6AKsa1pl3X/SWUAPvotc5kwRzdAocWRZcKuyIdCRNz2v3hWSfKpbjXcqKwKeFCsvKuiiRQruAJX4 rAybf2ktb0++MuvMBIyMcfEWakbScUlRpQD27Qib2+jeuGlVY8mTyLJDunoTWF6VdfJ99LKe4jvBD NHIqDfxvOISGNpPt+cSNGVfXDAwJsH/TLz94fb/9EzXZErZCUIDLH2ypPdg9NSU7xq2OBZgTMLKZn l/zH5R3FZnikl4Czt+RVpQLs1qiTVcUdBrTRq+bjjvD4I32SmtnJInWTvP1ET4xEY6dVFm0UBy4S0 +VU/OID+Q==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1iaSRE-0007TB-JM; Thu, 28 Nov 2019 22:39:04 +0000 Date: Thu, 28 Nov 2019 14:39:04 -0800 From: Matthew Wilcox To: Wei Yang Cc: "Kirill A. Shutemov" , Wei Yang , akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] mm/page_vma_mapped: page table boundary is already guaranteed Message-ID: <20191128223904.GG20752@bombadil.infradead.org> References: <20191128010321.21730-1-richardw.yang@linux.intel.com> <20191128010321.21730-2-richardw.yang@linux.intel.com> <20191128083143.kwih655snxqa2qnm@box.shutemov.name> <20191128210945.6gtt7wlygsvxip4n@master> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191128210945.6gtt7wlygsvxip4n@master> User-Agent: Mutt/1.12.1 (2019-06-15) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Nov 28, 2019 at 09:09:45PM +0000, Wei Yang wrote: > On Thu, Nov 28, 2019 at 11:31:43AM +0300, Kirill A. Shutemov wrote: > >On Thu, Nov 28, 2019 at 09:03:21AM +0800, Wei Yang wrote: > >> The check here is to guarantee pvmw->address iteration is limited in one > >> page table boundary. To be specific, here the address range should be in > >> one PMD_SIZE. > >> > >> If my understanding is correct, this check is already done in the above > >> check: > >> > >> address >= __vma_address(page, vma) + PMD_SIZE > >> > >> The boundary check here seems not necessary. > >> > >> Signed-off-by: Wei Yang > > > >NAK. > > > >THP can be mapped with PTE not aligned to PMD_SIZE. Consider mremap(). > > > > Hi, Kirill > > Thanks for your comment during Thanks Giving Day. Happy holiday:-) > > I didn't think about this case before, thanks for reminding. Then I tried to > understand your concern. > > mremap() would expand/shrink a memory mapping. In this case, probably shrink > is in concern. Since pvmw->page and pvmw->vma are not changed in the loop, the > case you mentioned maybe pvmw->page is the head of a THP but part of it is > unmapped. mremap() can also move a mapping, see MREMAP_FIXED. > This means the following condition stands: > > vma->vm_start <= vma_address(page) > vma->vm_end <= vma_address(page) + page_size(page) > > Since we have checked address with vm_end, do you think this case is also > guarded? > > Not sure my understanding is correct, look forward your comments. > > >> Test: > >> more than 48 hours kernel build test shows this code is not touched. > > > >Not an argument. I doubt mremap(2) is ever called in kernel build > >workload. > > > >-- > > Kirill A. Shutemov > > -- > Wei Yang > Help you, Help me >