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=-9.8 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_GIT 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 CCCFEC10F14 for ; Thu, 10 Oct 2019 13:59:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B03EA20B7C for ; Thu, 10 Oct 2019 13:59:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726192AbfJJN7V (ORCPT ); Thu, 10 Oct 2019 09:59:21 -0400 Received: from mga18.intel.com ([134.134.136.126]:58818 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726028AbfJJN7V (ORCPT ); Thu, 10 Oct 2019 09:59:21 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 10 Oct 2019 06:59:20 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.67,280,1566889200"; d="scan'208";a="277785443" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by orsmga001.jf.intel.com with ESMTP; 10 Oct 2019 06:59:17 -0700 From: Wei Yang To: akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, jglisse@redhat.com, mike.kravetz@oracle.com, riel@surriel.com, khlebnikov@yandex-team.ru, cai@lca.pw, shakeelb@google.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Wei Yang Subject: [Patch v2 1/2] mm/rmap.c: don't reuse anon_vma if we just want a copy Date: Thu, 10 Oct 2019 21:58:24 +0800 Message-Id: <20191010135825.28153-1-richardw.yang@linux.intel.com> X-Mailer: git-send-email 2.17.1 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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; -- 2.17.1