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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,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 93CE0C10F11 for ; Wed, 24 Apr 2019 14:28:14 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D730720811 for ; Wed, 24 Apr 2019 14:28:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D730720811 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 44q2jR4svjzDqQt for ; Thu, 25 Apr 2019 00:28:11 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=linux.ibm.com (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=ldufour@linux.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.ibm.com 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 44q2gT6t68zDqMt for ; Thu, 25 Apr 2019 00:26:29 +1000 (AEST) Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x3OEQ65c105312 for ; Wed, 24 Apr 2019 10:26:28 -0400 Received: from e06smtp04.uk.ibm.com (e06smtp04.uk.ibm.com [195.75.94.100]) by mx0a-001b2d01.pphosted.com with ESMTP id 2s2s71sehm-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 24 Apr 2019 10:26:27 -0400 Received: from localhost by e06smtp04.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Wed, 24 Apr 2019 15:26:11 +0100 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x3OEQ9pH53280928 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 24 Apr 2019 14:26:09 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8DA09AE053; Wed, 24 Apr 2019 14:26:09 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id DE32AAE063; Wed, 24 Apr 2019 14:26:06 +0000 (GMT) Received: from [9.145.176.48] (unknown [9.145.176.48]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 24 Apr 2019 14:26:06 +0000 (GMT) Subject: Re: [PATCH v12 20/31] mm: introduce vma reference counter To: Jerome Glisse References: <20190416134522.17540-1-ldufour@linux.ibm.com> <20190416134522.17540-21-ldufour@linux.ibm.com> <20190422203647.GK14666@redhat.com> From: Laurent Dufour Date: Wed, 24 Apr 2019 16:26:06 +0200 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190422203647.GK14666@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19042414-0016-0000-0000-0000027321E2 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19042414-0017-0000-0000-000032CF943C Message-Id: <122dd37e-f071-bdc1-b7f4-887d7cee766f@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-04-24_09:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 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-1904240113 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: jack@suse.cz, sergey.senozhatsky.work@gmail.com, peterz@infradead.org, Will Deacon , mhocko@kernel.org, linux-mm@kvack.org, paulus@samba.org, Punit Agrawal , hpa@zytor.com, Michel Lespinasse , Alexei Starovoitov , Andrea Arcangeli , ak@linux.intel.com, Minchan Kim , aneesh.kumar@linux.ibm.com, x86@kernel.org, Matthew Wilcox , Daniel Jordan , Ingo Molnar , David Rientjes , paulmck@linux.vnet.ibm.com, Haiyan Song , npiggin@gmail.com, sj38.park@gmail.com, dave@stgolabs.net, kemi.wang@intel.com, kirill@shutemov.name, Thomas Gleixner , zhong jiang , Ganesh Mahendran , Yang Shi , Mike Rapoport , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Sergey Senozhatsky , vinayak menon , akpm@linux-foundation.org, Tim Chen , haren@linux.vnet.ibm.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Le 22/04/2019 à 22:36, Jerome Glisse a écrit : > On Tue, Apr 16, 2019 at 03:45:11PM +0200, Laurent Dufour wrote: >> The final goal is to be able to use a VMA structure without holding the >> mmap_sem and to be sure that the structure will not be freed in our back. >> >> The lockless use of the VMA will be done through RCU protection and thus a >> dedicated freeing service is required to manage it asynchronously. >> >> As reported in a 2010's thread [1], this may impact file handling when a >> file is still referenced while the mapping is no more there. As the final >> goal is to handle anonymous VMA in a speculative way and not file backed >> mapping, we could close and free the file pointer in a synchronous way, as >> soon as we are guaranteed to not use it without holding the mmap_sem. For >> sanity reason, in a minimal effort, the vm_file file pointer is unset once >> the file pointer is put. >> >> [1] https://lore.kernel.org/linux-mm/20100104182429.833180340@chello.nl/ >> >> Signed-off-by: Laurent Dufour > > Using kref would have been better from my POV even with RCU freeing > but anyway: > > Reviewed-by: Jérôme Glisse Thanks Jérôme, I think kref is a good option here, I'll give it a try. >> --- >> include/linux/mm.h | 4 ++++ >> include/linux/mm_types.h | 3 +++ >> mm/internal.h | 27 +++++++++++++++++++++++++++ >> mm/mmap.c | 13 +++++++++---- >> 4 files changed, 43 insertions(+), 4 deletions(-) >> >> diff --git a/include/linux/mm.h b/include/linux/mm.h >> index f14b2c9ddfd4..f761a9c65c74 100644 >> --- a/include/linux/mm.h >> +++ b/include/linux/mm.h >> @@ -529,6 +529,9 @@ static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm) >> vma->vm_mm = mm; >> vma->vm_ops = &dummy_vm_ops; >> INIT_LIST_HEAD(&vma->anon_vma_chain); >> +#ifdef CONFIG_SPECULATIVE_PAGE_FAULT >> + atomic_set(&vma->vm_ref_count, 1); >> +#endif >> } >> >> static inline void vma_set_anonymous(struct vm_area_struct *vma) >> @@ -1418,6 +1421,7 @@ static inline void INIT_VMA(struct vm_area_struct *vma) >> INIT_LIST_HEAD(&vma->anon_vma_chain); >> #ifdef CONFIG_SPECULATIVE_PAGE_FAULT >> seqcount_init(&vma->vm_sequence); >> + atomic_set(&vma->vm_ref_count, 1); >> #endif >> } >> >> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h >> index 24b3f8ce9e42..6a6159e11a3f 100644 >> --- a/include/linux/mm_types.h >> +++ b/include/linux/mm_types.h >> @@ -285,6 +285,9 @@ struct vm_area_struct { >> /* linked list of VM areas per task, sorted by address */ >> struct vm_area_struct *vm_next, *vm_prev; >> >> +#ifdef CONFIG_SPECULATIVE_PAGE_FAULT >> + atomic_t vm_ref_count; >> +#endif >> struct rb_node vm_rb; >> >> /* >> diff --git a/mm/internal.h b/mm/internal.h >> index 9eeaf2b95166..302382bed406 100644 >> --- a/mm/internal.h >> +++ b/mm/internal.h >> @@ -40,6 +40,33 @@ void page_writeback_init(void); >> >> vm_fault_t do_swap_page(struct vm_fault *vmf); >> >> + >> +extern void __free_vma(struct vm_area_struct *vma); >> + >> +#ifdef CONFIG_SPECULATIVE_PAGE_FAULT >> +static inline void get_vma(struct vm_area_struct *vma) >> +{ >> + atomic_inc(&vma->vm_ref_count); >> +} >> + >> +static inline void put_vma(struct vm_area_struct *vma) >> +{ >> + if (atomic_dec_and_test(&vma->vm_ref_count)) >> + __free_vma(vma); >> +} >> + >> +#else >> + >> +static inline void get_vma(struct vm_area_struct *vma) >> +{ >> +} >> + >> +static inline void put_vma(struct vm_area_struct *vma) >> +{ >> + __free_vma(vma); >> +} >> +#endif /* CONFIG_SPECULATIVE_PAGE_FAULT */ >> + >> void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *start_vma, >> unsigned long floor, unsigned long ceiling); >> >> diff --git a/mm/mmap.c b/mm/mmap.c >> index f7f6027a7dff..c106440dcae7 100644 >> --- a/mm/mmap.c >> +++ b/mm/mmap.c >> @@ -188,6 +188,12 @@ static inline void mm_write_sequnlock(struct mm_struct *mm) >> } >> #endif /* CONFIG_SPECULATIVE_PAGE_FAULT */ >> >> +void __free_vma(struct vm_area_struct *vma) >> +{ >> + mpol_put(vma_policy(vma)); >> + vm_area_free(vma); >> +} >> + >> /* >> * Close a vm structure and free it, returning the next. >> */ >> @@ -200,8 +206,8 @@ static struct vm_area_struct *remove_vma(struct vm_area_struct *vma) >> vma->vm_ops->close(vma); >> if (vma->vm_file) >> fput(vma->vm_file); >> - mpol_put(vma_policy(vma)); >> - vm_area_free(vma); >> + vma->vm_file = NULL; >> + put_vma(vma); >> return next; >> } >> >> @@ -990,8 +996,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, >> if (next->anon_vma) >> anon_vma_merge(vma, next); >> mm->map_count--; >> - mpol_put(vma_policy(next)); >> - vm_area_free(next); >> + put_vma(next); >> /* >> * In mprotect's case 6 (see comments on vma_merge), >> * we must remove another next too. It would clutter >> -- >> 2.21.0 >> >