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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 42892ECE58D for ; Fri, 11 Oct 2019 01:24:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2566F21D56 for ; Fri, 11 Oct 2019 01:24:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728228AbfJKBYW (ORCPT ); Thu, 10 Oct 2019 21:24:22 -0400 Received: from mga01.intel.com ([192.55.52.88]:35610 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728201AbfJKBYT (ORCPT ); Thu, 10 Oct 2019 21:24:19 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 10 Oct 2019 18:24:18 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.67,282,1566889200"; d="scan'208";a="193388536" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by fmsmga008.fm.intel.com with ESMTP; 10 Oct 2019 18:24:16 -0700 Date: Fri, 11 Oct 2019 09:23:59 +0800 From: Wei Yang To: Konstantin Khlebnikov Cc: Wei Yang , akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, jglisse@redhat.com, mike.kravetz@oracle.com, riel@surriel.com, cai@lca.pw, shakeelb@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [Patch v2 1/2] mm/rmap.c: don't reuse anon_vma if we just want a copy Message-ID: <20191011012359.GA3883@richard> Reply-To: Wei Yang References: <20191010135825.28153-1-richardw.yang@linux.intel.com> <2a8a03bb-de72-62b0-1cb6-bc9b3b68b258@yandex-team.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2a8a03bb-de72-62b0-1cb6-bc9b3b68b258@yandex-team.ru> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 10, 2019 at 06:29:32PM +0300, Konstantin Khlebnikov wrote: >On 10/10/2019 16.58, Wei Yang wrote: >> Before commit 7a3ef208e662 ("mm: prevent endless growth of anon_vma >> hierarchy"), anon_vma_clone() doesn't change dst->anon_vma. While after >> this commit, anon_vma_clone() will try to reuse an exist one on forking. >> >> But this commit go a little bit further for the case not forking. >> anon_vma_clone() is called from __vma_split(), __split_vma(), copy_vma() >> and anon_vma_fork(). For the first three places, the purpose here is get >> a copy of src and we don't expect to touch dst->anon_vma even it is >> NULL. While after that commit, it is possible to reuse an anon_vma when >> dst->anon_vma is NULL. This is not we intend to have. > >In all these cases dst->anon_vma is a copy of src->anon_vma except >anon_vma_fork where dst_>anon_vma explicitly set to NULL before call. > >So reuse == true iff (!dst->anon_vma && src->anon_vma) > Ok, I think you are right. Thanks >> >> This patch stop reuse anon_vma for non-fork cases. >> >> Fix commit 7a3ef208e662 ("mm: prevent endless growth of anon_vma >> hierarchy") >> >> Signed-off-by: Wei Yang >> --- >> include/linux/rmap.h | 3 ++- >> mm/mmap.c | 6 +++--- >> mm/rmap.c | 7 ++++--- >> 3 files changed, 9 insertions(+), 7 deletions(-) >> >> diff --git a/include/linux/rmap.h b/include/linux/rmap.h >> index 988d176472df..963e6ab09b9b 100644 >> --- a/include/linux/rmap.h >> +++ b/include/linux/rmap.h >> @@ -142,7 +142,8 @@ static inline void anon_vma_unlock_read(struct anon_vma *anon_vma) >> void anon_vma_init(void); /* create anon_vma_cachep */ >> int __anon_vma_prepare(struct vm_area_struct *); >> void unlink_anon_vmas(struct vm_area_struct *); >> -int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *); >> +int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src, >> + bool reuse); >> int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *); >> static inline int anon_vma_prepare(struct vm_area_struct *vma) >> diff --git a/mm/mmap.c b/mm/mmap.c >> index 93f221785956..21e94f8ac4c7 100644 >> --- a/mm/mmap.c >> +++ b/mm/mmap.c >> @@ -791,7 +791,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, >> int error; >> importer->anon_vma = exporter->anon_vma; >> - error = anon_vma_clone(importer, exporter); >> + error = anon_vma_clone(importer, exporter, false); >> if (error) >> return error; >> } >> @@ -2666,7 +2666,7 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma, >> if (err) >> goto out_free_vma; >> - err = anon_vma_clone(new, vma); >> + err = anon_vma_clone(new, vma, false); >> if (err) >> goto out_free_mpol; >> @@ -3247,7 +3247,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap, >> new_vma->vm_pgoff = pgoff; >> if (vma_dup_policy(vma, new_vma)) >> goto out_free_vma; >> - if (anon_vma_clone(new_vma, vma)) >> + if (anon_vma_clone(new_vma, vma, false)) >> goto out_free_mempol; >> if (new_vma->vm_file) >> get_file(new_vma->vm_file); >> diff --git a/mm/rmap.c b/mm/rmap.c >> index d9a23bb773bf..f729e4013613 100644 >> --- a/mm/rmap.c >> +++ b/mm/rmap.c >> @@ -258,7 +258,8 @@ static inline void unlock_anon_vma_root(struct anon_vma *root) >> * good chance of avoiding scanning the whole hierarchy when it searches where >> * page is mapped. >> */ >> -int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) >> +int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src, >> + bool reuse) >> { >> struct anon_vma_chain *avc, *pavc; >> struct anon_vma *root = NULL; >> @@ -286,7 +287,7 @@ int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) >> * will always reuse it. Root anon_vma is never reused: >> * it has self-parent reference and at least one child. >> */ >> - if (!dst->anon_vma && anon_vma != src->anon_vma && >> + if (reuse && !dst->anon_vma && anon_vma != src->anon_vma && >> anon_vma->degree < 2) >> dst->anon_vma = anon_vma; >> } >> @@ -329,7 +330,7 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) >> * First, attach the new VMA to the parent VMA's anon_vmas, >> * so rmap can find non-COWed pages in child processes. >> */ >> - error = anon_vma_clone(vma, pvma); >> + error = anon_vma_clone(vma, pvma, true); >> if (error) >> return error; >> -- Wei Yang Help you, Help me