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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 5B9E0C282CE for ; Wed, 22 May 2019 22:06:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0CE7521883 for ; Wed, 22 May 2019 22:06:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729707AbfEVWGx (ORCPT ); Wed, 22 May 2019 18:06:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58364 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726363AbfEVWGw (ORCPT ); Wed, 22 May 2019 18:06:52 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 430608553D; Wed, 22 May 2019 22:06:52 +0000 (UTC) Received: from redhat.com (unknown [10.20.6.178]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3DC6218205; Wed, 22 May 2019 22:06:51 +0000 (UTC) Date: Wed, 22 May 2019 18:06:49 -0400 From: Jerome Glisse To: Ralph Campbell Cc: Jason Gunthorpe , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, Leon Romanovsky , Doug Ledford , Artemy Kovalyov , Moni Shoua , Mike Marciniszyn , Kaike Wan , Dennis Dalessandro Subject: Re: [PATCH v4 0/1] Use HMM for ODP v4 Message-ID: <20190522220649.GC20179@redhat.com> References: <20190411181314.19465-1-jglisse@redhat.com> <20190506195657.GA30261@ziepe.ca> <20190521205321.GC3331@redhat.com> <20190522005225.GA30819@ziepe.ca> <20190522174852.GA23038@redhat.com> <20190522201247.GH6054@ziepe.ca> <05e7f491-b8a4-4214-ab75-9ecf1128aaa6@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <05e7f491-b8a4-4214-ab75-9ecf1128aaa6@nvidia.com> User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Wed, 22 May 2019 22:06:52 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 22, 2019 at 02:12:31PM -0700, Ralph Campbell wrote: > > On 5/22/19 1:12 PM, Jason Gunthorpe wrote: > > On Wed, May 22, 2019 at 01:48:52PM -0400, Jerome Glisse wrote: > > > > > static void put_per_mm(struct ib_umem_odp *umem_odp) > > > { > > > struct ib_ucontext_per_mm *per_mm = umem_odp->per_mm; > > > @@ -325,9 +283,10 @@ static void put_per_mm(struct ib_umem_odp *umem_odp) > > > up_write(&per_mm->umem_rwsem); > > > WARN_ON(!RB_EMPTY_ROOT(&per_mm->umem_tree.rb_root)); > > > - mmu_notifier_unregister_no_release(&per_mm->mn, per_mm->mm); > > > + hmm_mirror_unregister(&per_mm->mirror); > > > put_pid(per_mm->tgid); > > > - mmu_notifier_call_srcu(&per_mm->rcu, free_per_mm); > > > + > > > + kfree(per_mm); > > > > Notice that mmu_notifier only uses SRCU to fence in-progress ops > > callbacks, so I think hmm internally has the bug that this ODP > > approach prevents. > > > > hmm should follow the same pattern ODP has and 'kfree_srcu' the hmm > > struct, use container_of in the mmu_notifier callbacks, and use the > > otherwise vestigal kref_get_unless_zero() to bail: > > You might also want to look at my patch where > I try to fix some of these same issues (5/5). > > https://marc.info/?l=linux-mm&m=155718572908765&w=2 I need to review the patchset but i do not want to invert referencing ie having mm hold reference on hmm. Will review tommorrow. I wanted to do that today but did not had time.