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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 66962EB64DA for ; Wed, 5 Jul 2023 17:14:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id ED6CF8D0002; Wed, 5 Jul 2023 13:14:14 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E87078D0001; Wed, 5 Jul 2023 13:14:14 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D27808D0002; Wed, 5 Jul 2023 13:14:14 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id C2DA88D0001 for ; Wed, 5 Jul 2023 13:14:14 -0400 (EDT) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 714FA802E0 for ; Wed, 5 Jul 2023 17:14:14 +0000 (UTC) X-FDA: 80978206428.27.458E23E Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf22.hostedemail.com (Postfix) with ESMTP id DE524C0019 for ; Wed, 5 Jul 2023 17:14:11 +0000 (UTC) Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=cEpVzpnI; spf=pass (imf22.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1688577252; a=rsa-sha256; cv=none; b=NWRgjvgm+ykwy6pRSsQgCZJ4b7JWWx1BRjwIb9ijErdy1GKuvlQ/AqsPlkrMgJAqnuS6eW ZR3ekJIinMDfwkGASMZVhTP1+xbPM6O1k4XjJi7N4FJ+0MpxvVTDV5zpvM41yE43Wcd7h4 bNQo47huMGKmYYK7TNcWoAVN1FSCrcA= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=cEpVzpnI; spf=pass (imf22.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1688577252; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=a6fxBPBS9mNaQm6LSrIZd4vdKlGZL91VslAI6+By/As=; b=5EJH0AbHaTzyA6i/XfBhQMqHuw8GXgLInQE3xy/EpqrLEFwX0gQ/9ERdsORcgN9aTOrN+4 LI3A/wOCVvruYwCJ/EurW+38O68AKRqv9gOm2Osb88xCCk13YcJy7Upilv8mowyKTIS1KG nF1k9CQL+HmtG2zePajsWEISjQDJhzQ= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1688577251; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=a6fxBPBS9mNaQm6LSrIZd4vdKlGZL91VslAI6+By/As=; b=cEpVzpnIqlXaz7GZ9lHcTeVcpcDTTWQeVgiLgEyAzNeCSCQLrEpeYoO7qn6MtuTNsiStGY HhxNiNLpTYk1oxvMKX3/miUP5SFl7Cm3kLC+0xYQ4Jx3Q0MqL2ckxIQnZNpm8wyFjSGfRh 1ZFBESZDAX3da8dp64dY29yqmNhFJcI= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-433-kuOZW0sRP_aaifwHeAoUPA-1; Wed, 05 Jul 2023 13:14:10 -0400 X-MC-Unique: kuOZW0sRP_aaifwHeAoUPA-1 Received: by mail-wm1-f71.google.com with SMTP id 5b1f17b1804b1-3fa8d203eccso5001365e9.1 for ; Wed, 05 Jul 2023 10:14:09 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1688577249; x=1691169249; h=content-transfer-encoding:in-reply-to:organization:from:references :cc:to:content-language:subject:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=a6fxBPBS9mNaQm6LSrIZd4vdKlGZL91VslAI6+By/As=; b=Zc11aNeBxeBh7ybbwm/nElppXdBtwi/lCbhe9H4694aRHNBYoO/hdg/pGCDiIVFkuy RIcMYCN/rbo88j5ATU4p6D02k1/24nvR5g7coPrqrUrnw/wKjOX6rWYglBqiKsuDG/K7 1DLp8f57oCtv/fZFgRZTTe8wh+OkQZtNcGDI31oo+M//WC+/XaojagFZ5YaHRIp2DnlE +vZhhs8Bf6D9ESVBnqCCgogF8fIh/s9PC+aOCfP+0jVPeVBPGu10Sbat3nMxgA901Vk9 FVWZHS4sLA0g0yBP3Q66diolQh/BUM/SvA1iwMRWXR1ca8eEGLR1fxXTfcvrCzi0SXEI HFrg== X-Gm-Message-State: ABy/qLbF6j8TCN1+0ZjqGEKd/YoEX7lrdcYLDhGjbTOjseTh6RkpMm9h Q3Q9dLL2gnrHuvqsIc3rXDcX0tDCCskExbvWdtb9aBqfYiBRuuFi14RnC0PhEf3i6ZV5nNxGucu CxV2DTyPcw+Y= X-Received: by 2002:a1c:790a:0:b0:3fb:af9a:bf30 with SMTP id l10-20020a1c790a000000b003fbaf9abf30mr2843841wme.2.1688577248747; Wed, 05 Jul 2023 10:14:08 -0700 (PDT) X-Google-Smtp-Source: APBJJlGeCuf/W6MTtkOf7dX+nc3d9EnWYOlr9nA7OJpij/WlD4Ds+urw6/DQsIfBD5eA8hOzT3n4/A== X-Received: by 2002:a1c:790a:0:b0:3fb:af9a:bf30 with SMTP id l10-20020a1c790a000000b003fbaf9abf30mr2843806wme.2.1688577248380; Wed, 05 Jul 2023 10:14:08 -0700 (PDT) Received: from ?IPV6:2003:cb:c71a:1c00:e2b1:fc33:379b:a713? (p200300cbc71a1c00e2b1fc33379ba713.dip0.t-ipconnect.de. [2003:cb:c71a:1c00:e2b1:fc33:379b:a713]) by smtp.gmail.com with ESMTPSA id c8-20020a056000104800b003143ba62cf4sm6547606wrx.86.2023.07.05.10.14.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 05 Jul 2023 10:14:07 -0700 (PDT) Message-ID: <10c8fe17-fa9b-bf34-cb88-c758e07c9d72@redhat.com> Date: Wed, 5 Jul 2023 19:14:05 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH v3 1/2] fork: lock VMAs of the parent process when forking To: Suren Baghdasaryan , akpm@linux-foundation.org Cc: jirislaby@kernel.org, jacobly.alt@gmail.com, holger@applied-asynchrony.com, hdegoede@redhat.com, michel@lespinasse.org, jglisse@google.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mgorman@techsingularity.net, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, peterz@infradead.org, ldufour@linux.ibm.com, paulmck@kernel.org, mingo@redhat.com, will@kernel.org, luto@kernel.org, songliubraving@fb.com, peterx@redhat.com, dhowells@redhat.com, hughd@google.com, bigeasy@linutronix.de, kent.overstreet@linux.dev, punit.agrawal@bytedance.com, lstoakes@gmail.com, peterjung1337@gmail.com, rientjes@google.com, chriscli@google.com, axelrasmussen@google.com, joelaf@google.com, minchan@google.com, rppt@kernel.org, jannh@google.com, shakeelb@google.com, tatashin@google.com, edumazet@google.com, gthelen@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20230705171213.2843068-1-surenb@google.com> <20230705171213.2843068-2-surenb@google.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230705171213.2843068-2-surenb@google.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: DE524C0019 X-Stat-Signature: x9wcrspdswx1mkx1y6fhdqpx73f4ghk7 X-Rspam-User: X-HE-Tag: 1688577251-396358 X-HE-Meta: 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 fY9DUX5y 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 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 05.07.23 19:12, Suren Baghdasaryan wrote: > When forking a child process, parent write-protects an anonymous page > and COW-shares it with the child being forked using copy_present_pte(). > Parent's TLB is flushed right before we drop the parent's mmap_lock in > dup_mmap(). If we get a write-fault before that TLB flush in the parent, > and we end up replacing that anonymous page in the parent process in > do_wp_page() (because, COW-shared with the child), this might lead to > some stale writable TLB entries targeting the wrong (old) page. > Similar issue happened in the past with userfaultfd (see flush_tlb_page() > call inside do_wp_page()). > Lock VMAs of the parent process when forking a child, which prevents > concurrent page faults during fork operation and avoids this issue. > This fix can potentially regress some fork-heavy workloads. Kernel build > time did not show noticeable regression on a 56-core machine while a > stress test mapping 10000 VMAs and forking 5000 times in a tight loop > shows ~5% regression. If such fork time regression is unacceptable, > disabling CONFIG_PER_VMA_LOCK should restore its performance. Further > optimizations are possible if this regression proves to be problematic. > > Suggested-by: David Hildenbrand > Reported-by: Jiri Slaby > Closes: https://lore.kernel.org/all/dbdef34c-3a07-5951-e1ae-e9c6e3cdf51b@kernel.org/ > Reported-by: Holger Hoffstätte > Closes: https://lore.kernel.org/all/b198d649-f4bf-b971-31d0-e8433ec2a34c@applied-asynchrony.com/ > Reported-by: Jacob Young > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217624 > Fixes: 0bff0aaea03e ("x86/mm: try VMA lock-based page fault handling first") > Cc: stable@vger.kernel.org > Signed-off-by: Suren Baghdasaryan > --- > kernel/fork.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/kernel/fork.c b/kernel/fork.c > index b85814e614a5..403bc2b72301 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -658,6 +658,12 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, > retval = -EINTR; > goto fail_uprobe_end; > } > +#ifdef CONFIG_PER_VMA_LOCK > + /* Disallow any page faults before calling flush_cache_dup_mm */ > + for_each_vma(old_vmi, mpnt) > + vma_start_write(mpnt); > + vma_iter_init(&old_vmi, oldmm, 0); > +#endif > flush_cache_dup_mm(oldmm); > uprobe_dup_mmap(oldmm, mm); > /* The old version was most probably fine as well, but this certainly looks even safer. Acked-by: David Hildenbrand -- Cheers, David / dhildenb