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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 05289C433EF for ; Wed, 6 Apr 2022 01:56:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1383123AbiDFB4m (ORCPT ); Tue, 5 Apr 2022 21:56:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37680 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1357028AbiDEUj4 (ORCPT ); Tue, 5 Apr 2022 16:39:56 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F1DA72E68D for ; Tue, 5 Apr 2022 13:19:43 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 635AD6199D for ; Tue, 5 Apr 2022 20:17:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BE3C4C385A1; Tue, 5 Apr 2022 20:17:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1649189834; bh=8/l+ZtJfoPJoB4kQ08MB4S4Te7j45ssQbej1Ml5v3XE=; h=Date:To:From:Subject:From; b=VKGmosJcasU62GBX+C2NqfEAiX9HyVVYouJXzEarU8YejDARbOc/RNuNNF1066dl1 aWIaSr0Dz+Z4sGAm+JNKubdwDYsLlwivw1qoe5S1U1d/5UGqPd562AoPNTDVFoXmlb XTbuunxYW/O7g3aiJ+ksUjskWoEtw08s1BSbjiLU= Date: Tue, 05 Apr 2022 13:17:14 -0700 To: mm-commits@vger.kernel.org, willy@infradead.org, rppt@linux.vnet.ibm.com, nadav.amit@gmail.com, mike.kravetz@oracle.com, kirill@shutemov.name, jglisse@redhat.com, hughd@google.com, david@redhat.com, axelrasmussen@google.com, apopple@nvidia.com, aarcange@redhat.com, peterx@redhat.com, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-khugepaged-dont-recycle-vma-pgtable-if-uffd-wp-registered.patch added to -mm tree Message-Id: <20220405201714.BE3C4C385A1@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: mm/khugepaged: don't recycle vma pgtable if uffd-wp registered has been added to the -mm tree. Its filename is mm-khugepaged-dont-recycle-vma-pgtable-if-uffd-wp-registered.patch This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-khugepaged-dont-recycle-vma-pgtable-if-uffd-wp-registered.patch and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-khugepaged-dont-recycle-vma-pgtable-if-uffd-wp-registered.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Peter Xu Subject: mm/khugepaged: don't recycle vma pgtable if uffd-wp registered When we're trying to collapse a 2M huge shmem page, don't retract pgtable pmd page if it's registered with uffd-wp, because that pgtable could have pte markers installed. Recycling of that pgtable means we'll lose the pte markers. That could cause data loss for an uffd-wp enabled application on shmem. Instead of disabling khugepaged on these files, simply skip retracting these special VMAs, then the page cache can still be merged into a huge thp, and other mm/vma can still map the range of file with a huge thp when proper. Note that checking VM_UFFD_WP needs to be done with mmap_sem held for write, that avoids race like: khugepaged user thread ========== =========== check VM_UFFD_WP, not set UFFDIO_REGISTER with uffd-wp on shmem wr-protect some pages (install markers) take mmap_sem write lock erase pmd and free pmd page --> pte markers are dropped unnoticed! Link: https://lkml.kernel.org/r/20220405014921.14994-1-peterx@redhat.com Signed-off-by: Peter Xu Cc: Alistair Popple Cc: Andrea Arcangeli Cc: Axel Rasmussen Cc: David Hildenbrand Cc: Hugh Dickins Cc: Jerome Glisse Cc: "Kirill A . Shutemov" Cc: Matthew Wilcox Cc: Mike Kravetz Cc: Mike Rapoport Cc: Nadav Amit Signed-off-by: Andrew Morton --- mm/khugepaged.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) --- a/mm/khugepaged.c~mm-khugepaged-dont-recycle-vma-pgtable-if-uffd-wp-registered +++ a/mm/khugepaged.c @@ -1474,6 +1474,10 @@ void collapse_pte_mapped_thp(struct mm_s if (!hugepage_vma_check(vma, vma->vm_flags | VM_HUGEPAGE)) return; + /* Keep pmd pgtable for uffd-wp; see comment in retract_page_tables() */ + if (userfaultfd_wp(vma)) + return; + hpage = find_lock_page(vma->vm_file->f_mapping, linear_page_index(vma, haddr)); if (!hpage) @@ -1609,7 +1613,15 @@ static void retract_page_tables(struct a * reverse order. Trylock is a way to avoid deadlock. */ if (mmap_write_trylock(mm)) { - if (!khugepaged_test_exit(mm)) + /* + * When a vma is registered with uffd-wp, we can't + * recycle the pmd pgtable because there can be pte + * markers installed. Skip it only, so the rest mm/vma + * can still have the same file mapped hugely, however + * it'll always mapped in small page size for uffd-wp + * registered ranges. + */ + if (!khugepaged_test_exit(mm) && !userfaultfd_wp(vma)) collapse_and_free_pmd(mm, vma, addr, pmd); mmap_write_unlock(mm); } else { _ Patches currently in -mm which might be from peterx@redhat.com are mm-introduce-pte_marker-swap-entry.patch mm-teach-core-mm-about-pte-markers.patch mm-check-against-orig_pte-for-finish_fault.patch mm-uffd-pte_marker_uffd_wp.patch mm-shmem-take-care-of-uffdio_copy_mode_wp.patch mm-shmem-handle-uffd-wp-special-pte-in-page-fault-handler.patch mm-shmem-persist-uffd-wp-bit-across-zapping-for-file-backed.patch mm-shmem-allow-uffd-wr-protect-none-pte-for-file-backed-mem.patch mm-shmem-allows-file-back-mem-to-be-uffd-wr-protected-on-thps.patch mm-shmem-handle-uffd-wp-during-fork.patch mm-hugetlb-introduce-huge-pte-version-of-uffd-wp-helpers.patch mm-hugetlb-hook-page-faults-for-uffd-write-protection.patch mm-hugetlb-take-care-of-uffdio_copy_mode_wp.patch mm-hugetlb-handle-uffdio_writeprotect.patch mm-hugetlb-handle-pte-markers-in-page-faults.patch mm-hugetlb-allow-uffd-wr-protect-none-ptes.patch mm-hugetlb-only-drop-uffd-wp-special-pte-if-required.patch mm-hugetlb-handle-uffd-wp-during-fork.patch mm-khugepaged-dont-recycle-vma-pgtable-if-uffd-wp-registered.patch mm-pagemap-recognize-uffd-wp-bit-for-shmem-hugetlbfs.patch mm-uffd-enable-write-protection-for-shmem-hugetlbfs.patch mm-enable-pte-markers-by-default.patch selftests-uffd-enable-uffd-wp-for-shmem-hugetlbfs.patch