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=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,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 87EF8ECE58E for ; Thu, 10 Oct 2019 15:29:41 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3F710214E0 for ; Thu, 10 Oct 2019 15:29:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=yandex-team.ru header.i=@yandex-team.ru header.b="kln/o57q" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3F710214E0 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=yandex-team.ru Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id D263E6B0003; Thu, 10 Oct 2019 11:29:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id CD6B86B0005; Thu, 10 Oct 2019 11:29:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BC4948E0003; Thu, 10 Oct 2019 11:29:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0113.hostedemail.com [216.40.44.113]) by kanga.kvack.org (Postfix) with ESMTP id 948BB6B0003 for ; Thu, 10 Oct 2019 11:29:40 -0400 (EDT) Received: from smtpin30.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with SMTP id 0A4FA6D98 for ; Thu, 10 Oct 2019 15:29:40 +0000 (UTC) X-FDA: 76028259720.30.able98_370bdb44b6b2f X-HE-Tag: able98_370bdb44b6b2f X-Filterd-Recvd-Size: 6852 Received: from forwardcorp1j.mail.yandex.net (forwardcorp1j.mail.yandex.net [5.45.199.163]) by imf30.hostedemail.com (Postfix) with ESMTP for ; Thu, 10 Oct 2019 15:29:37 +0000 (UTC) Received: from mxbackcorp1j.mail.yandex.net (mxbackcorp1j.mail.yandex.net [IPv6:2a02:6b8:0:1619::162]) by forwardcorp1j.mail.yandex.net (Yandex) with ESMTP id 0D2A62E1483; Thu, 10 Oct 2019 18:29:35 +0300 (MSK) Received: from iva4-c987840161f8.qloud-c.yandex.net (iva4-c987840161f8.qloud-c.yandex.net [2a02:6b8:c0c:3da5:0:640:c987:8401]) by mxbackcorp1j.mail.yandex.net (nwsmtp/Yandex) with ESMTP id znRYN9zoAO-TWdKZLvE; Thu, 10 Oct 2019 18:29:35 +0300 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex-team.ru; s=default; t=1570721375; bh=rvyQZNR5vejzJwf/NPJDq1pLl/nAVUWK8QqpP27blPw=; h=In-Reply-To:Message-ID:From:Date:References:To:Subject:Cc; b=kln/o57qo7sxteBOZTJemTgM0vB/jr8scazNYd6cqZTgphDG7ZyOPbP6+stj6CFaW KkSFLAQy67YfHme4oci4K+EeRI0+muSmlP7EZOjf0ij6Fj46kLok9Da0SvCqZFu38K GCmoax4G7fGKaomtWKC6m+b57JjiHV4fh8HoKh1c= Authentication-Results: mxbackcorp1j.mail.yandex.net; dkim=pass header.i=@yandex-team.ru Received: from dynamic-red.dhcp.yndx.net (dynamic-red.dhcp.yndx.net [2a02:6b8:0:40c:3d4d:a9cb:ef29:4bb1]) by iva4-c987840161f8.qloud-c.yandex.net (nwsmtp/Yandex) with ESMTPSA id dZ2BPwa0ho-TWI4Cfoo; Thu, 10 Oct 2019 18:29:32 +0300 (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client certificate not present) Subject: Re: [Patch v2 1/2] mm/rmap.c: don't reuse anon_vma if we just want a copy To: 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 Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20191010135825.28153-1-richardw.yang@linux.intel.com> From: Konstantin Khlebnikov Message-ID: <2a8a03bb-de72-62b0-1cb6-bc9b3b68b258@yandex-team.ru> Date: Thu, 10 Oct 2019 18:29:32 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20191010135825.28153-1-richardw.yang@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-CA Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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) > > 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; > >