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=-12.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_PASS autolearn=unavailable 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 9E2C9C04AA7 for ; Mon, 13 May 2019 17:23:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 65B542084A for ; Mon, 13 May 2019 17:23:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="S6jaG8Ep" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731648AbfEMRXd (ORCPT ); Mon, 13 May 2019 13:23:33 -0400 Received: from hqemgate15.nvidia.com ([216.228.121.64]:19077 "EHLO hqemgate15.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731636AbfEMRX3 (ORCPT ); Mon, 13 May 2019 13:23:29 -0400 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqemgate15.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Mon, 13 May 2019 10:22:49 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Mon, 13 May 2019 10:23:28 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Mon, 13 May 2019 10:23:28 -0700 Received: from rcampbell-dev.nvidia.com (10.124.1.5) by HQMAIL101.nvidia.com (172.20.187.10) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Mon, 13 May 2019 17:23:28 +0000 Subject: Re: [PATCH 4/5] mm/hmm: hmm_vma_fault() doesn't always call hmm_range_unregister() To: Jerome Glisse CC: Souptick Joarder , Linux-MM , , John Hubbard , Ira Weiny , Dan Williams , Arnd Bergmann , Balbir Singh , Dan Carpenter , Matthew Wilcox , Andrew Morton References: <20190506232942.12623-1-rcampbell@nvidia.com> <20190506232942.12623-5-rcampbell@nvidia.com>

<20190512150724.GA4238@redhat.com> From: Ralph Campbell Message-ID: <43d3eab0-acf9-e823-8b62-6e692e7b6ec5@nvidia.com> Date: Mon, 13 May 2019 10:23:27 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.0 MIME-Version: 1.0 In-Reply-To: <20190512150724.GA4238@redhat.com> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To HQMAIL101.nvidia.com (172.20.187.10) Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1557768169; bh=n8vpRjGW5GPHF+IO0n302JSczsEWtzgDfOElD0ZndA8=; h=X-PGP-Universal:Subject:To:CC:References:From:Message-ID:Date: User-Agent:MIME-Version:In-Reply-To:X-Originating-IP: X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=S6jaG8EpUHqREXnq/w6qes8gG0EhywAaS9pjrQa5P3fPTjRND/mXesGNWHI5zh5lS MCAZhXIcQpxJz2UIHCdK1sL59SAJWTaEu7ZDnUT2d0A8dqAI/XxT4Yv+Y1wfM4y7Ql JccyVUf0+urKTYCR3NG8sQn3XcNnn+f4txkkgZaL4DuBd1beY4b9uS0DRS58ifa2ZY mEisv1qr0a8+ZfeXUTn/EvHyMtY1tPBgXuqwLTlWXICwW1Xru8PS3DUf6guSMS+nQF dN/t4rnbMWPqrllLWmMx/goWpph2WFgLe9x6Hcm4NXGbdH5b7Kneot0A4EmuKA/Juh J2mWd5McJixXg== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/12/19 8:07 AM, Jerome Glisse wrote: > On Tue, May 07, 2019 at 11:12:14AM -0700, Ralph Campbell wrote: >> >> On 5/7/19 6:15 AM, Souptick Joarder wrote: >>> On Tue, May 7, 2019 at 5:00 AM wrote: >>>> >>>> From: Ralph Campbell >>>> >>>> The helper function hmm_vma_fault() calls hmm_range_register() but is >>>> missing a call to hmm_range_unregister() in one of the error paths. >>>> This leads to a reference count leak and ultimately a memory leak on >>>> struct hmm. >>>> >>>> Always call hmm_range_unregister() if hmm_range_register() succeeded. >>> >>> How about * Call hmm_range_unregister() in error path if >>> hmm_range_register() succeeded* ? >> >> Sure, sounds good. >> I'll include that in v2. > > NAK for the patch see below why > >> >>>> >>>> Signed-off-by: Ralph Campbell >>>> Cc: John Hubbard >>>> Cc: Ira Weiny >>>> Cc: Dan Williams >>>> Cc: Arnd Bergmann >>>> Cc: Balbir Singh >>>> Cc: Dan Carpenter >>>> Cc: Matthew Wilcox >>>> Cc: Souptick Joarder >>>> Cc: Andrew Morton >>>> --- >>>> include/linux/hmm.h | 3 ++- >>>> 1 file changed, 2 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/include/linux/hmm.h b/include/linux/hmm.h >>>> index 35a429621e1e..fa0671d67269 100644 >>>> --- a/include/linux/hmm.h >>>> +++ b/include/linux/hmm.h >>>> @@ -559,6 +559,7 @@ static inline int hmm_vma_fault(struct hmm_range *range, bool block) >>>> return (int)ret; >>>> >>>> if (!hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT)) { >>>> + hmm_range_unregister(range); >>>> /* >>>> * The mmap_sem was taken by driver we release it here and >>>> * returns -EAGAIN which correspond to mmap_sem have been >>>> @@ -570,13 +571,13 @@ static inline int hmm_vma_fault(struct hmm_range *range, bool block) >>>> >>>> ret = hmm_range_fault(range, block); >>>> if (ret <= 0) { >>>> + hmm_range_unregister(range); >>> >>> what is the reason to moved it up ? >> >> I moved it up because the normal calling pattern is: >> down_read(&mm->mmap_sem) >> hmm_vma_fault() >> hmm_range_register() >> hmm_range_fault() >> hmm_range_unregister() >> up_read(&mm->mmap_sem) >> >> I don't think it is a bug to unlock mmap_sem and then unregister, >> it is just more consistent nesting. > > So this is not the usage pattern with HMM usage pattern is: > > hmm_range_register() > hmm_range_fault() > hmm_range_unregister() > > The hmm_vma_fault() is gonne so this patch here break thing. > > See https://cgit.freedesktop.org/~glisse/linux/log/?h=hmm-5.2-v3 The patch series is on top of v5.1-rc6-mmotm-2019-04-25-16-30. hmm_vma_fault() is defined there and in your hmm-5.2-v3 branch as a backward compatibility transition function in include/linux/hmm.h. So I agree the new API is to use hmm_range_register(), etc. This is intended to cover the transition period. Note that hmm_vma_fault() is being called from drivers/gpu/drm/nouveau/nouveau_svm.c in both trees.