From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3xhs274zllzDqGG for ; Wed, 30 Aug 2017 13:49:19 +1000 (AEST) Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v7U3msjU108952 for ; Tue, 29 Aug 2017 23:49:17 -0400 Received: from e23smtp02.au.ibm.com (e23smtp02.au.ibm.com [202.81.31.144]) by mx0a-001b2d01.pphosted.com with ESMTP id 2cnd16ggh3-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Tue, 29 Aug 2017 23:49:17 -0400 Received: from localhost by e23smtp02.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 30 Aug 2017 13:49:14 +1000 Received: from d23av02.au.ibm.com (d23av02.au.ibm.com [9.190.235.138]) by d23relay06.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v7U3nB4F42598536 for ; Wed, 30 Aug 2017 13:49:11 +1000 Received: from d23av02.au.ibm.com (localhost [127.0.0.1]) by d23av02.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id v7U3n0Nm013949 for ; Wed, 30 Aug 2017 13:49:02 +1000 Subject: Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure To: Peter Zijlstra , Laurent Dufour References: <1503007519-26777-1-git-send-email-ldufour@linux.vnet.ibm.com> <1503007519-26777-15-git-send-email-ldufour@linux.vnet.ibm.com> <20170827001823.n5wgkfq36z6snvf2@node.shutemov.name> <507e79d5-59df-c5b5-106d-970c9353d9bc@linux.vnet.ibm.com> <20170829120426.4ar56rbmiupbqmio@hirez.programming.kicks-ass.net> Cc: "Kirill A. Shutemov" , paulmck@linux.vnet.ibm.com, akpm@linux-foundation.org, ak@linux.intel.com, mhocko@kernel.org, dave@stgolabs.net, jack@suse.cz, Matthew Wilcox , benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org, Thomas Gleixner , Ingo Molnar , hpa@zytor.com, Will Deacon , linux-kernel@vger.kernel.org, linux-mm@kvack.org, haren@linux.vnet.ibm.com, khandual@linux.vnet.ibm.com, npiggin@gmail.com, bsingharora@gmail.com, Tim Chen , linuxppc-dev@lists.ozlabs.org, x86@kernel.org From: Anshuman Khandual Date: Wed, 30 Aug 2017 09:18:59 +0530 MIME-Version: 1.0 In-Reply-To: <20170829120426.4ar56rbmiupbqmio@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=windows-1252 Message-Id: <3da42409-6313-d710-5293-47426fac4808@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 08/29/2017 05:34 PM, Peter Zijlstra wrote: > On Tue, Aug 29, 2017 at 09:59:30AM +0200, Laurent Dufour wrote: >> On 27/08/2017 02:18, Kirill A. Shutemov wrote: >>>> + >>>> + if (unlikely(!vma->anon_vma)) >>>> + goto unlock; >>> It deserves a comment. >> You're right I'll add it in the next version. >> For the record, the root cause is that __anon_vma_prepare() requires the >> mmap_sem to be held because vm_next and vm_prev must be safe. > But should that test not be: > > if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) > goto unlock; This makes more sense. We are backing off from speculative path because struct anon_vma has not been created for this anonymous vma and we cannot do that without holding mmap_sem. This should have nothing to do with vma->vm_ops availability.