From nobody Mon Sep 15 23:19:50 2025 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 44D31C54EBD for ; Mon, 9 Jan 2023 20:56:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237757AbjAIU4L (ORCPT ); Mon, 9 Jan 2023 15:56:11 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34828 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237601AbjAIUz0 (ORCPT ); Mon, 9 Jan 2023 15:55:26 -0500 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5D7DC85C89 for ; Mon, 9 Jan 2023 12:54:28 -0800 (PST) Received: by mail-yb1-xb49.google.com with SMTP id n203-20020a2572d4000000b0078f09db9888so10253981ybc.18 for ; Mon, 09 Jan 2023 12:54:28 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=mttq8CcSxh6pk/PDvvqo/9XfYX/awSV+YKJHUec4DWQ=; b=EbLgVpiNWauCxYsPhZzluNh8i7Jc9od95XU7q4baD/bZuTFbACugKjaBqwn3ZlwjPK DyA2dJROokooe1X9hWF9cqxx7R8dzaLC4TQ2VgG1K6ZzCrV6Cn+bNgWtTm8qKV2EPlQI C3EgQy0lx8995KoeqPGehRxKjsY9DJj6pO/ydpCP34y4VCDsA5lFDA9xaQObsm54nagL gf/rqX49ePSI64VKn0w7yUB28hwRSupVRZyvn8G3inMqKMvhkMvaFS5iHqspfhqeeQGW sJQNxcx4h1OW/3tP5B8wZxgrbXFTXvC0zscvDZLigjE3sBlwiKuCEIrG4zHiBAmIFXhN sp1Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=mttq8CcSxh6pk/PDvvqo/9XfYX/awSV+YKJHUec4DWQ=; b=5WJWiABhMZgyLmuOtlK7476/RvLzIHRadz5DxklX2oNNchRgDf7QOrcl0lXIaZM+rR 7O24E38Nz2hBt7D+DiRjiCO+1yiKZDKuzWP9ukYeejYHZajSfiHQdDsKU8TQBEZ7HgBW apwQwp1VnW7eRKAGg1XNscCrG+AOmXQ42AcJdYvIY9V3HaTX4krx165n1zmvN8git6eq vwP0VngLOFBFdeyl/QJoXnzPX8m2iTucptrA4TyGz1N1XqzBYAQa+P6m8WYVw1UiGhzC Ux0N6YN/hxCCgIYmHF8jyTxndRI/dpTieLuhPMg1EOjQsk/qNRfHvp4BeeJkx2l1Im3e pfsQ== X-Gm-Message-State: AFqh2kr+c5dm96RGEXRTWU5v36UFKfwg817i4Mzjp6MmS1mYFm3LGt0a vXuLccAOiUf8JRBm3tkW8mzcDf/sL3Q= X-Google-Smtp-Source: AMrXdXsB8fbMiTP1DYP5J5XEU88bTBTK0YYISNp2DJzOoqciXF/+cmYxWMxqmdOzbjRBqH/+xJjk8vQehVo= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:200:9393:6f7a:d410:55ca]) (user=surenb job=sendgmr) by 2002:a25:850e:0:b0:6f8:42d8:2507 with SMTP id w14-20020a25850e000000b006f842d82507mr8097864ybk.110.1673297667509; Mon, 09 Jan 2023 12:54:27 -0800 (PST) Date: Mon, 9 Jan 2023 12:53:13 -0800 In-Reply-To: <20230109205336.3665937-1-surenb@google.com> Mime-Version: 1.0 References: <20230109205336.3665937-1-surenb@google.com> X-Mailer: git-send-email 2.39.0.314.g84b9a713c41-goog Message-ID: <20230109205336.3665937-19-surenb@google.com> Subject: [PATCH 18/41] mm/khugepaged: write-lock VMA while collapsing a huge page From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: 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, laurent.dufour@fr.ibm.com, paulmck@kernel.org, luto@kernel.org, songliubraving@fb.com, peterx@redhat.com, david@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, axelrasmussen@google.com, joelaf@google.com, minchan@google.com, jannh@google.com, shakeelb@google.com, tatashin@google.com, edumazet@google.com, gthelen@google.com, gurua@google.com, arjunroy@google.com, soheil@google.com, hughlynch@google.com, leewalsh@google.com, posk@google.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com, surenb@google.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Protect VMA from concurrent page fault handler while collapsing a huge page. Page fault handler needs a stable PMD to use PTL and relies on per-VMA lock to prevent concurrent PMD changes. pmdp_collapse_flush(), set_huge_pmd() and collapse_and_free_pmd() can modify a PMD, which will not be detected by a page fault handler without proper locking. Signed-off-by: Suren Baghdasaryan --- mm/khugepaged.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 5376246a3052..d8d0647f0c2c 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1032,6 +1032,7 @@ static int collapse_huge_page(struct mm_struct *mm, u= nsigned long address, if (result !=3D SCAN_SUCCEED) goto out_up_write; =20 + vma_write_lock(vma); anon_vma_lock_write(vma->anon_vma); =20 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm, @@ -1503,6 +1504,9 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, uns= igned long addr, goto drop_hpage; } =20 + /* Lock the vma before taking i_mmap and page table locks */ + vma_write_lock(vma); + /* * We need to lock the mapping so that from here on, only GUP-fast and * hardware page walks can access the parts of the page tables that @@ -1690,6 +1694,7 @@ static int retract_page_tables(struct address_space *= mapping, pgoff_t pgoff, result =3D SCAN_PTE_UFFD_WP; goto unlock_next; } + vma_write_lock(vma); collapse_and_free_pmd(mm, vma, addr, pmd); if (!cc->is_khugepaged && is_target) result =3D set_huge_pmd(vma, addr, pmd, hpage); --=20 2.39.0