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 39F4BC433FE for ; Tue, 8 Nov 2022 21:59:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230028AbiKHV7v (ORCPT ); Tue, 8 Nov 2022 16:59:51 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36848 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229769AbiKHV7u (ORCPT ); Tue, 8 Nov 2022 16:59:50 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B99C813CC3 for ; Tue, 8 Nov 2022 13:59:49 -0800 (PST) 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 4F056617AD for ; Tue, 8 Nov 2022 21:59:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A78BFC433C1; Tue, 8 Nov 2022 21:59:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1667944788; bh=SJpG/0aJ1i/82qHhlGq635kYvpqBHl5y0IQBF3uLbUs=; h=Date:To:From:Subject:From; b=Ln118v9qI0y+HEEQHQFUpcjOamxvbSDgHuaF/Cz7fO+DsTPpluyTtrA3pb19LTWCE yc7L9ul84eyma+jlt06eVCnhNjZR/SnY//d6FljNfFtmVYPAogtHgalG2m+fBaXmqP cr4141YTjnFpNqt38oa+w2EMkdijPKx/7Q7D2JCQ= Date: Tue, 08 Nov 2022 13:59:48 -0800 To: mm-commits@vger.kernel.org, vbabka@suse.cz, torvalds@linux-foundation.org, rppt@kernel.org, peterx@redhat.com, npiggin@gmail.com, namit@vmware.com, mpe@ellerman.id.au, mgorman@techsingularity.net, hughd@google.com, david@fromorbit.com, anshuman.khandual@arm.com, aarcange@redhat.com, david@redhat.com, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-mprotect-minor-can_change_pte_writable-cleanups.patch added to mm-unstable branch Message-Id: <20221108215948.A78BFC433C1@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/mprotect: minor can_change_pte_writable() cleanups has been added to the -mm mm-unstable branch. Its filename is mm-mprotect-minor-can_change_pte_writable-cleanups.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mprotect-minor-can_change_pte_writable-cleanups.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm 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 via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: David Hildenbrand Subject: mm/mprotect: minor can_change_pte_writable() cleanups Date: Tue, 8 Nov 2022 18:46:47 +0100 We want to replicate this code for handling PMDs soon. (1) No need to crash the kernel, warning and rejecting is good enough. As this will no longer get optimized out, drop the pte_write() check: no harm would be done. (2) Add a comment why PROT_NONE mapped pages are excluded. (3) Add a comment regarding MAP_SHARED handling and why we rely on the dirty bit in the PTE. Link: https://lkml.kernel.org/r/20221108174652.198904-3-david@redhat.com Signed-off-by: David Hildenbrand Cc: Andrea Arcangeli Cc: Anshuman Khandual Cc: Dave Chinner Cc: Hugh Dickins Cc: Linus Torvalds Cc: Mel Gorman Cc: Michael Ellerman Cc: Mike Rapoport Cc: Nadav Amit Cc: Nicholas Piggin Cc: Peter Xu Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- mm/mprotect.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) --- a/mm/mprotect.c~mm-mprotect-minor-can_change_pte_writable-cleanups +++ a/mm/mprotect.c @@ -44,8 +44,10 @@ static inline bool can_change_pte_writab { struct page *page; - VM_BUG_ON(!(vma->vm_flags & VM_WRITE) || pte_write(pte)); + if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE))) + return false; + /* Don't touch entries that are not even readable. */ if (pte_protnone(pte)) return false; @@ -59,15 +61,22 @@ static inline bool can_change_pte_writab if (!(vma->vm_flags & VM_SHARED)) { /* - * We can only special-case on exclusive anonymous pages, - * because we know that our write-fault handler similarly would - * map them writable without any additional checks while holding - * the PT lock. + * Writable MAP_PRIVATE mapping: We can only special-case on + * exclusive anonymous pages, because we know that our + * write-fault handler similarly would map them writable without + * any additional checks while holding the PT lock. */ page = vm_normal_page(vma, addr, pte); return page && PageAnon(page) && PageAnonExclusive(page); } + /* + * Writable MAP_SHARED mapping: "clean" might indicate that the FS still + * needs a real write-fault for writenotify + * (see vma_wants_writenotify()). If "dirty", the assumption is that the + * FS was already notified and we can simply mark the PTE writable + * just like the write-fault handler would do. + */ return pte_dirty(pte); } _ Patches currently in -mm which might be from david@redhat.com are selftests-vm-anon_cow-test-cow-handling-of-anonymous-memory.patch selftests-vm-anon_cow-test-cow-handling-of-anonymous-memory-fix.patch selftests-vm-factor-out-pagemap_is_populated-into-vm_util.patch selftests-vm-anon_cow-thp-tests.patch selftests-vm-anon_cow-hugetlb-tests.patch selftests-vm-anon_cow-add-liburing-test-cases.patch selftests-vm-anon_cow-add-liburing-test-cases-fix.patch mm-gup_test-start-stop-read-functionality-for-pin-longterm-test.patch mm-gup_test-start-stop-read-functionality-for-pin-longterm-test-fix.patch selftests-vm-anon_cow-add-r-o-longterm-tests-via-gup_test.patch selftests-vm-add-ksm-unmerge-tests.patch mm-pagewalk-dont-trigger-test_walk-in-walk_page_vma.patch selftests-vm-add-test-to-measure-madv_unmergeable-performance.patch mm-ksm-simplify-break_ksm-to-not-rely-on-vm_fault_write.patch mm-remove-vm_fault_write.patch mm-ksm-fix-ksm-cow-breaking-with-userfaultfd-wp-via-fault_flag_unshare.patch mm-pagewalk-add-walk_page_range_vma.patch mm-ksm-convert-break_ksm-to-use-walk_page_range_vma.patch mm-gup-remove-foll_migration.patch mm-mprotect-minor-can_change_pte_writable-cleanups.patch mm-huge_memory-try-avoiding-write-faults-when-changing-pmd-protection.patch mm-mprotect-factor-out-check-whether-manual-pte-write-upgrades-are-required.patch mm-autonuma-use-can_change_ptepmd_writable-to-replace-savedwrite.patch mm-remove-unused-savedwrite-infrastructure.patch selftests-vm-anon_cow-add-mprotect-optimization-tests.patch