From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 D5D4B38DC6C for ; Sat, 10 Oct 2026 21:39:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791668394; cv=none; b=F4jY+GIDMKs+elIbp7tK3pGDJP5TuwAyeT+QPQbLYSyT7KVmmnJTW1pzf9SvwiNcULvcS0rOWDpvHrPfxM1O87RBq+gIOCLAUqZc7CnWftZs1bQewykj31cOIpNY+Ok0sjlK6OCXNBq/AOE0ySk5jubMTQJYN6gm1j3pK1f9ybw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791668394; c=relaxed/simple; bh=MHlwsa8bF/HZb6o/cwTJ1Ute5mDWAPwN0LbeUX5SP7s=; h=Date:To:From:Subject:Message-Id; b=hA5HilRpYF9SxJ02GaPU99VK176Bh6xT+FlfgyOp26bncrGN3NBR8ZegrfAvHrBVZWhYlHkvmqO4XRMbjM3ILdps21dHSQ3SGhhKtBnW5HKMgX/RZznWJmRv5TLsHH1XsyZUYkPPKC9AvTRHgZCoPKkPwEaBruxcLIshNMO4XM8= 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=0+r/lZt2; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="0+r/lZt2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AB7F91F000FF; Sat, 10 Oct 2026 21:39:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1791668389; bh=mpAiPVH+U07rAJPv6NQuJ+seMcK5SX1j7Z6fzreCfCM=; h=Date:To:From:Subject; b=0+r/lZt2HlNfLsiP6XAGt6Y3nbf52A/ZV1Mi6FmbGXuXxPhUSv33g846OdGfaAvEZ TnyMIIC++97hyYRUi+s6NCJ+JsjbPfT7b/IknTuL5urT9vFTIx1RW+6mKa62dK9Fa/ Tw1EpOpGmDpPQBRsBau7U08fqeEi2PIgQd1bNq8M= Date: Sat, 10 Oct 2026 14:39:49 -0700 To: mm-commits@vger.kernel.org,ljs@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: [to-be-updated] mm-mlock-eliminate-weird-vma_io_bit-abuse-and-simplify.patch removed from -mm tree Message-Id: <20261010213949.AB7F91F000FF@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm/mlock: eliminate weird VMA_IO_BIT abuse and simplify has been removed from the -mm tree. Its filename was mm-mlock-eliminate-weird-vma_io_bit-abuse-and-simplify.patch This patch was dropped because an updated version will be issued ------------------------------------------------------ From: "Lorenzo Stoakes (ARM)" Subject: mm/mlock: eliminate weird VMA_IO_BIT abuse and simplify Date: Sat, 03 Oct 2026 17:32:54 +0100 When performing mlock() or munlock() otherwise normal VMAs have VMA_IO_BIT solely to fix a race with migration which might otherwise double-count mlock VMAs. This is unnecessary - at the point of applying folio mlock state, whether setting or clearing PG_mlocked, we know whether or not we are locking. Solve this in two ways - thread a boolean through the page table walk indicating whether a lock or unlock is being performed, and run a locking walk with VMA_LOCKONFAULT_BIT set and VMA_LOCKED_BIT cleared. This state never occurs otherwise, as VMA_LOCKONFAULT_BIT always implies VMA_LOCKED_BIT. These are also always cleared together. Then, update folio_add_lru_vma() and mlock_folio() to check only for VMA_LOCKED_BIT, and update try_to_unmap_one() to check for VMA_LOCKED_MASK instead. Also remove the useless invocation of allow_mlock_munlock() which simply returns true if unlocking and instead rename it to allow_mlock() and only call it when locking. With the other mlock abuse of VMA_IO_BIT addressed, update mlock_vma_folio() and folio_add_lru_vma() to simply test for VMA_LOCKED_BIT. The munlock_vma_folio() function tests VMA_LOCKED_MASK instead, as an unmap racing with the locking walk must still munlock folios the walk has already counted. Additionally, in order to ensure a racing unmap/migration releases the reference munlock_folio() took (whose put was batched), check VMA_LOCKED_MASK before calling mlock_drain_local() in try_to_unmap_one() and try_to_migrate_one(). While here, also replace some deprecated VMA flag predicates. Link: https://lore.kernel.org/20261003-b4-mmap-prepare-vma-flag-sanify-v4-23-a1f052500fd7@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Signed-off-by: Andrew Morton Reviewed-by: Zi Yan Cc: Liam R. Howlett Cc: Vlastimil Babka Cc: Jann Horn Cc: Pedro Falcato Cc: David Hildenbrand Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Michal Hocko Cc: Jonathan Corbet Cc: Greg Kroah-Hartman Cc: Dennis Dalessandro Cc: Jason Gunthorpe Cc: Leon Romanovsky Cc: Paul Moore Cc: Stephen Smalley Cc: Jaroslav Kysela Cc: Takashi Iwai Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: Andrii Nakryiko Cc: Eduard Zingerman Cc: Kumar Kartikeya Dwivedi Cc: Baolin Wang Cc: Nico Pache Cc: Ryan Roberts Cc: Dev Jain Cc: Barry Song Cc: Lance Yang Cc: Usama Arif Cc: Kiryl Shutsemau Cc: Doug Gilbert Cc: James Bottomley Cc: Martin K. Petersen Cc: Simona Vetter Cc: Helge Deller Cc: Sebastian Reichel Cc: John Hubbard Cc: Peter Xu Cc: Masami Hiramatsu Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: Arnaldo Carvalho de Melo Cc: Namhyung Kim Cc: Mark Rutland Cc: Rik van Riel Cc: Harry Yoo Cc: Juri Lelli Cc: Vincent Guittot Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Thomas Zimmermann Cc: David Airlie Cc: Will Deacon Cc: Aneesh Kumar K.V Cc: Nicholas Piggin Cc: Arnd Bergmann Cc: Muchun Song Cc: Oscar Salvador Cc: Matthew Wilcox (Oracle) Cc: Jan Kara Cc: Marc Zyngier Cc: Oliver Upton Cc: Catalin Marinas Cc: Madhavan Srinivasan Cc: Anup Patel Cc: Paul Walmsley Cc: Palmer Dabbelt Cc: Albert Ou Cc: Christian Borntraeger Cc: Janosch Frank Cc: Claudio Imbrenda Cc: Alexander Gordeev Cc: Gerald Schaefer Cc: Heiko Carstens Cc: Vasily Gorbik Cc: David S. Miller Cc: Andreas Larsson Cc: Al Viro Cc: Christian Brauner Cc: Matthew Brost Cc: Joshua Hahn Cc: Rakie Kim Cc: Byungchul Park Cc: Gregory Price Cc: Ying Huang Cc: Alistair Popple Cc: Chris Li Cc: Kairui Song Cc: Kemeng Shi Cc: Nhat Pham Cc: Baoquan He Cc: Youngjun Park Cc: Johannes Weiner Cc: Qi Zheng Cc: Shakeel Butt Cc: Axel Rasmussen Cc: Yuanchu Xie Cc: Wei Xu Cc: Chengming Zhou Cc: Michal Hocko Cc: Miklos Szeredi Cc: Xu Xin --- mm/folio.c | 2 - mm/internal.h | 10 ++++++--- mm/mlock.c | 51 +++++++++++++++++------------------------------- mm/rmap.c | 8 ++++--- 4 files changed, 32 insertions(+), 39 deletions(-) --- a/mm/folio.c~mm-mlock-eliminate-weird-vma_io_bit-abuse-and-simplify +++ a/mm/folio.c @@ -505,7 +505,7 @@ void folio_add_lru_vma(struct folio *fol { VM_BUG_ON_FOLIO(folio_test_lru(folio), folio); - if (unlikely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) == VM_LOCKED)) + if (vma_test(vma, VMA_LOCKED_BIT)) mlock_new_folio(folio); else folio_add_lru(folio); --- a/mm/internal.h~mm-mlock-eliminate-weird-vma_io_bit-abuse-and-simplify +++ a/mm/internal.h @@ -970,8 +970,7 @@ void mlock_folio(struct folio *folio); static inline void mlock_vma_folio(struct folio *folio, struct vm_area_struct *vma) { - /* The VM_IO check prevents migration from double-counting during mlock. */ - if (unlikely((vma->vm_flags & (VM_LOCKED|VM_SPECIAL)) == VM_LOCKED)) + if (vma_test(vma, VMA_LOCKED_BIT)) mlock_folio(folio); } @@ -988,7 +987,12 @@ static inline void munlock_vma_folio(str * always munlock the folio and page reclaim will correct it * if it's wrong. */ - if (unlikely(vma->vm_flags & VM_LOCKED)) + /* + * VMA_LOCKONFAULT_BIT alone marks an mlock walk in progress, see + * mlock_vma_pages_range(). An unmap racing with the walk must still + * munlock folios the walk has already counted. + */ + if (unlikely(vma_test_any_mask(vma, VMA_LOCKED_MASK))) munlock_folio(folio); } --- a/mm/mlock.c~mm-mlock-eliminate-weird-vma_io_bit-abuse-and-simplify +++ a/mm/mlock.c @@ -316,22 +316,10 @@ static inline unsigned int folio_mlock_s return folio_pte_batch(folio, pte, ptent, count); } -static inline bool allow_mlock_munlock(struct folio *folio, +static inline bool allow_mlock(struct folio *folio, struct vm_area_struct *vma, unsigned long start, unsigned long end, unsigned int step) { - /* - * For unlock, allow munlock large folio which is partially - * mapped to VMA. As it's possible that large folio is - * mlocked and VMA is split later. - * - * During memory pressure, such kind of large folio can - * be split. And the pages are not in VM_LOCKed VMA - * can be reclaimed. - */ - if (!vma_test(vma, VMA_LOCKED_BIT)) - return true; - /* folio_within_range() cannot take KSM, but any small folio is OK */ if (!folio_test_large(folio)) return true; @@ -352,6 +340,7 @@ static int mlock_pte_range(pmd_t *pmd, u { struct vm_area_struct *vma = walk->vma; + const bool lock = walk->private; spinlock_t *ptl; pte_t *start_pte, *pte; pte_t ptent; @@ -368,7 +357,7 @@ static int mlock_pte_range(pmd_t *pmd, u folio = pmd_folio(*pmd); if (folio_is_zone_device(folio)) goto out; - if (vma_test(vma, VMA_LOCKED_BIT)) + if (lock) mlock_folio(folio); else munlock_folio(folio); @@ -390,10 +379,10 @@ static int mlock_pte_range(pmd_t *pmd, u continue; step = folio_mlock_step(folio, pte, addr, end); - if (!allow_mlock_munlock(folio, vma, start, end, step)) + if (lock && !allow_mlock(folio, vma, start, end, step)) goto next_entry; - if (vma_test(vma, VMA_LOCKED_BIT)) + if (lock) mlock_folio(folio); else munlock_folio(folio); @@ -428,31 +417,29 @@ static void mlock_vma_pages_range(struct .pmd_entry = mlock_pte_range, .walk_lock = PGWALK_WRLOCK_VERIFY, }; + const bool lock = vma_flags_test(new_vma_flags, VMA_LOCKED_BIT); + vma_flags_t walk_flags = *new_vma_flags; /* - * There is a slight chance that concurrent page migration, - * or page reclaim finding a page of this now-VMA_LOCKED_BIT vma, - * will call mlock_vma_folio() and raise page's mlock_count: - * double counting, leaving the page unevictable indefinitely. - * Communicate this danger to mlock_vma_folio() with VMA_IO_BIT, - * which is a VMA_SPECIAL_FLAGS flag not allowed on VMA_LOCKED_BIT vmas. - * mmap_lock is held in write mode here, so this weird - * combination should not be visible to other mmap_lock users; - * but WRITE_ONCE so rmap walkers must see VMA_IO_BIT if VMA_LOCKED_BIT. + * LOCKONFAULT without LOCKED never otherwise occurs: it marks a walk in + * progress so that rmap-side callers, which test VMA_LOCKED_BIT, do not + * count folios, while try_to_unmap_one(), which tests VMA_LOCKED_MASK, + * still refuses to unmap them. */ - if (vma_flags_test(new_vma_flags, VMA_LOCKED_BIT)) - vma_flags_set(new_vma_flags, VMA_IO_BIT); + if (lock) { + vma_flags_clear(&walk_flags, VMA_LOCKED_BIT); + vma_flags_set(&walk_flags, VMA_LOCKONFAULT_BIT); + } + vma_start_write(vma); - vma_flags_reset_once(vma, new_vma_flags); + vma_flags_reset_once(vma, &walk_flags); lru_add_drain(); - walk_page_range_vma(vma, start, end, &mlock_walk_ops, NULL); + walk_page_range_vma(vma, start, end, &mlock_walk_ops, (void *)lock); lru_add_drain(); - if (vma_flags_test(new_vma_flags, VMA_IO_BIT)) { - vma_flags_clear(new_vma_flags, VMA_IO_BIT); + if (lock) vma_flags_reset_once(vma, new_vma_flags); - } } /* --- a/mm/rmap.c~mm-mlock-eliminate-weird-vma_io_bit-abuse-and-simplify +++ a/mm/rmap.c @@ -2239,9 +2239,11 @@ static bool try_to_unmap_one(struct foli /* * If the folio is in an mlock()d vma, we must not swap it out. + * VMA_LOCKONFAULT_BIT alone marks an mlock walk in progress, see + * mlock_vma_pages_range(). */ if (!(flags & TTU_IGNORE_MLOCK) && - (vma->vm_flags & VM_LOCKED)) { + vma_test_any_mask(vma, VMA_LOCKED_MASK)) { ptes++; /* @@ -2395,7 +2397,7 @@ static bool try_to_unmap_one(struct foli } finish_unmap: folio_remove_rmap_ptes(folio, page, nr_pages, vma); - if (vma->vm_flags & VM_LOCKED) + if (vma_test_any_mask(vma, VMA_LOCKED_MASK)) mlock_drain_local(); folio_put_refs(folio, nr_pages); @@ -2770,7 +2772,7 @@ static bool try_to_migrate_one(struct fo hugetlb_remove_rmap(folio); else folio_remove_rmap_pte(folio, subpage, vma); - if (vma->vm_flags & VM_LOCKED) + if (vma_test_any_mask(vma, VMA_LOCKED_MASK)) mlock_drain_local(); folio_put(folio); } _ Patches currently in -mm which might be from ljs@kernel.org are mm-vma-enforce-that-mm-managed-mappings-may-not-set-vma_io_bit.patch mm-remove-vma_io_bit-check-in-vma_is_mm_managed.patch mm-remove-hugetlb_inlineh.patch mm-rename-is_vm_hugetlb_page-to-vma_is_hugetlb.patch mm-drop-some-redundant-checks-around-hugetlb-vmas.patch mm-madvise-update-is_valid_guard_vma-to-use-vma_can_merge.patch mm-vma-introduce-vma_is_mm_backed.patch mm-uffd-use-predicates-for-userfaultfd-checks.patch mm-madvise-use-predicates-for-madvise-madv_dofork.patch mm-eliminate-vma_special_flags-usage-when-hugetlb-explicitly-tested.patch mm-eliminate-vma_special_flags-check-in-lru_gen_look_around.patch mm-avoid-use-of-vma_special_flags-in-migrate_vma_setup.patch mm-eliminate-vm_special-vma_special_flags.patch fuse-dax-do-not-set-vm_mixedmap.patch mm-huge_memory-remove-vma_is_special_huge.patch mm-vma-const-ify-vma_assert_stabilised-and-associated-functions.patch mm-implement-and-use-vma_has_anon_rmap-silence-kcsan.patch mm-update-comments-to-refer-to-anon-rmap-rather-than-anon_vma.patch mm-vma-dont-remove-vma-from-rmap-if-pgoff-unchanged.patch