From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D78CA1DB125 for ; Fri, 7 Nov 2025 19:07:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762542452; cv=none; b=u15vZCqI4ez8cHOWWEvqHshvy97eZoukdVJOtJdnI4luUJyIbbkIhVSFaEHCdbB4I7+KQODICLRyqvFLwaZfl+OiP1KZ5H7F9Hlc3ZbJimosbm7fEOPlRpB+Uqcg3kADv8YB5nqT9cklKzQvm71jZ5CNv2eF+YRU5vGYb+9c8EA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762542452; c=relaxed/simple; bh=jtHUqpr3nFPcICYhbaBSvZW4+JZz3AODXX+VdjB3PAg=; h=Date:To:From:Subject:Message-Id; b=QmHQL9CZdQdl1NWcnu9vDD+NBX7uy/1XwGhuJH/iCkRxktsiQzyHwKkRU8RUauomef7bN/Xm4j7XPAP6mgsA7RLBNofY/Sbw2KBMpwG0M1RMNtO8yx28ML9XZdKj3Xj0RILpHAZ7u4wrhikvJz6lEZMCU58cvLLbBYF/h1oLzkE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=ChsHbqgf; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="ChsHbqgf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5FC64C4CEF5; Fri, 7 Nov 2025 19:07:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1762542452; bh=jtHUqpr3nFPcICYhbaBSvZW4+JZz3AODXX+VdjB3PAg=; h=Date:To:From:Subject:From; b=ChsHbqgfhWXSydO5L2fFjjjkK6sW8d6LBmx/+IOZwV7ix5mKqRh6AVATh9AZAJacQ 4ng+lq/pOe69oVcpihdXvg0WG33QENnSI1ZTQXAOpUP/ozCJSBjrW2YMzUaicr2Ras xVNIZWrZJak56wggLtvx+k2eHRUsQbL81x2MmLX4= Date: Fri, 07 Nov 2025 11:07:31 -0800 To: mm-commits@vger.kernel.org,vbabka@suse.cz,pfalcato@suse.de,lorenzo.stoakes@oracle.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-add-atomic-vma-flags-and-set-vm_maybe_guard-as-such.patch added to mm-new branch Message-Id: <20251107190732.5FC64C4CEF5@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm: add atomic VMA flags and set VM_MAYBE_GUARD as such has been added to the -mm mm-new branch. Its filename is mm-add-atomic-vma-flags-and-set-vm_maybe_guard-as-such.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-add-atomic-vma-flags-and-set-vm_maybe_guard-as-such.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. 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: Lorenzo Stoakes Subject: mm: add atomic VMA flags and set VM_MAYBE_GUARD as such Date: Fri, 7 Nov 2025 16:11:47 +0000 This patch adds the ability to atomically set VMA flags with only the mmap read/VMA read lock held. As this could be hugely problematic for VMA flags in general given that all other accesses are non-atomic and serialised by the mmap/VMA locks, we implement this with a strict allow-list - that is, only designated flags are allowed to do this. We make VM_MAYBE_GUARD one of these flags. Link: https://lkml.kernel.org/r/cda9d4c073d773ef6c2cf2939d66cf80544cff40.1762531708.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes Reviewed-by: Pedro Falcato Reviewed-by: Vlastimil Babka Signed-off-by: Andrew Morton --- include/linux/mm.h | 42 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) --- a/include/linux/mm.h~mm-add-atomic-vma-flags-and-set-vm_maybe_guard-as-such +++ a/include/linux/mm.h @@ -518,6 +518,9 @@ extern unsigned int kobjsize(const void /* This mask represents all the VMA flag bits used by mlock */ #define VM_LOCKED_MASK (VM_LOCKED | VM_LOCKONFAULT) +/* These flags can be updated atomically via VMA/mmap read lock. */ +#define VM_ATOMIC_SET_ALLOWED VM_MAYBE_GUARD + /* Arch-specific flags to clear when updating VM flags on protection change */ #ifndef VM_ARCH_CLEAR # define VM_ARCH_CLEAR VM_NONE @@ -860,6 +863,45 @@ static inline void vm_flags_mod(struct v __vm_flags_mod(vma, set, clear); } +static inline bool __vma_flag_atomic_valid(struct vm_area_struct *vma, + int bit) +{ + const vm_flags_t mask = BIT(bit); + + /* Only specific flags are permitted */ + if (WARN_ON_ONCE(!(mask & VM_ATOMIC_SET_ALLOWED))) + return false; + + return true; +} + +/* + * Set VMA flag atomically. Requires only VMA/mmap read lock. Only specific + * valid flags are allowed to do this. + */ +static inline void vma_flag_set_atomic(struct vm_area_struct *vma, int bit) +{ + /* mmap read lock/VMA read lock must be held. */ + if (!rwsem_is_locked(&vma->vm_mm->mmap_lock)) + vma_assert_locked(vma); + + if (__vma_flag_atomic_valid(vma, bit)) + set_bit(bit, &vma->__vm_flags); +} + +/* + * Test for VMA flag atomically. Requires no locks. Only specific valid flags + * are allowed to do this. + * + * This is necessarily racey, so callers must ensure that serialisation is + * achieved through some other means, or that races are permissible. + */ +static inline bool vma_flag_test_atomic(struct vm_area_struct *vma, int bit) +{ + if (__vma_flag_atomic_valid(vma, bit)) + return test_bit(bit, &vma->__vm_flags); +} + static inline void vma_set_anonymous(struct vm_area_struct *vma) { vma->vm_ops = NULL; _ Patches currently in -mm which might be from lorenzo.stoakes@oracle.com are mm-shmem-update-shmem-to-use-mmap_prepare.patch device-dax-update-devdax-to-use-mmap_prepare.patch mm-vma-remove-unused-function-make-internal-functions-static.patch mm-add-vma_desc_size-vma_desc_pages-helpers.patch relay-update-relay-to-use-mmap_prepare.patch mm-vma-rename-__mmap_prepare-function-to-avoid-confusion.patch mm-add-remap_pfn_range_prepare-remap_pfn_range_complete.patch mm-abstract-io_remap_pfn_range-based-on-pfn.patch mm-introduce-io_remap_pfn_range_.patch mm-add-ability-to-take-further-action-in-vm_area_desc.patch doc-update-porting-vfs-documentation-for-mmap_prepare-actions.patch mm-hugetlbfs-update-hugetlbfs-to-use-mmap_prepare.patch mm-add-shmem_zero_setup_desc.patch mm-update-mem-char-driver-to-use-mmap_prepare.patch mm-update-resctl-to-use-mmap_prepare.patch mm-vma-small-vma-lock-cleanups.patch mm-correctly-handle-uffd-pte-markers.patch mm-introduce-leaf-entry-type-and-use-to-simplify-leaf-entry-logic.patch mm-introduce-leaf-entry-type-and-use-to-simplify-leaf-entry-logic-fix.patch mm-avoid-unnecessary-uses-of-is_swap_pte.patch mm-eliminate-uses-of-is_swap_pte-when-leafent_from_pte-suffices.patch mm-use-leaf-entries-in-debug-pgtable-remove-is_swap_pte.patch fs-proc-task_mmu-refactor-pagemap_pmd_range.patch mm-avoid-unnecessary-use-of-is_swap_pmd.patch mm-huge_memory-refactor-copy_huge_pmd-non-present-logic.patch mm-huge_memory-refactor-change_huge_pmd-non-present-logic.patch mm-replace-pmd_to_swp_entry-with-leafent_from_pmd.patch mm-replace-pmd_to_swp_entry-with-leafent_from_pmd-fix.patch mm-introduce-pmd_is_huge-and-use-where-appropriate.patch mm-remove-remaining-is_swap_pmd-users-and-is_swap_pmd.patch mm-remove-non_swap_entry-and-use-leaf-entry-helpers-instead.patch mm-remove-non_swap_entry-and-use-leaf-entry-helpers-instead-fix.patch mm-remove-is_hugetlb_entry_.patch mm-eliminate-further-swapops-predicates.patch mm-replace-remaining-pte_to_swp_entry-with-leafent_from_pte.patch mm-introduce-vm_maybe_guard-and-make-visible-in-proc-pid-smaps.patch mm-add-atomic-vma-flags-and-set-vm_maybe_guard-as-such.patch mm-implement-sticky-vma-flags.patch mm-introduce-copy-on-fork-vmas-and-make-vm_maybe_guard-one.patch mm-set-the-vm_maybe_guard-flag-on-guard-region-install.patch tools-testing-vma-add-vma-sticky-userland-tests.patch tools-testing-selftests-mm-add-madv_collapse-test-case.patch tools-testing-selftests-mm-add-smaps-visibility-guard-region-test.patch