Re: [PATCH v2 1/5] mm: Make per-VMA locks available universally
From: Suren Baghdasaryan
Date: Thu Jun 11 2026 - 15:30:39 EST
On Wed, Jun 10, 2026 at 4:04 PM Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> wrote:
>
>
> From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
>
> The per-VMA locks have been around for several years. They've had some
> bugs worked out of them and have seen quite wide use. However, they
> are still only available when architectures explicitly enable them.
> Remove the conditional compilation around the per-VMA locks, making
> them available on all architectures and configs.
>
> The approach up to now seemed to be to add ARCH_SUPPORTS_PER_VMA_LOCK
> when the architecture started using per-VMA locks in the fault
> handler. But, contrary to the naming, the Kconfig option does not
> really indicate whether the architecture supports per-VMA locks or
> not. It is more of a marker for whether the architecture is likely to
> benefit from per-VMA locks.
Correct. Originally per-VMA locks were used only in the page fault
handling path and architectures that used them in that path would set
ARCH_SUPPORTS_PER_VMA_LOCK. Over time these locks are used in more
places, so ARCH_SUPPORTS_PER_VMA_LOCK lost its meaning and indeed can
be removed.
>
> To me, the most important thing side-effect of universal availability
> is letting per-VMA locks be used in SMP=n configs. This lets us use
> per-VMA locking in all x86 code without fallbacks.
>
> Overall, this just generally makes the kernel simpler. Just look at
> the diffstat. It also opens the door to users that want to use the
> per-VMA locks in common code. Doing *that* brings additional
> simplifications.
>
> The downside of this is adding some fields to vm_area_struct and
> mm_struct. There are likely ways to optimize this, especially for
> things like SMP=n configs. For now, do the simplest thing: use the
> same implementation everywhere.
>
> Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Reviewed-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
> Cc: Lorenzo Stoakes <ljs@xxxxxxxxxx>
> Cc: Vlastimil Babka <vbabka@xxxxxxxxxx>
> Cc: Shakeel Butt <shakeel.butt@xxxxxxxxx>
> Cc: linux-mm@xxxxxxxxx
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Arve Hjønnevåg <arve@xxxxxxxxxxx>
> Cc: Todd Kjos <tkjos@xxxxxxxxxxx>
> Cc: Christian Brauner <christian@xxxxxxxxxx>
> Cc: Carlos Llamas <cmllamas@xxxxxxxxxx>
> Cc: Alice Ryhl <aliceryhl@xxxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: David Ahern <dsahern@xxxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx
>
> --
>
> Changes from v1:
> * Remove a bunch of left over CONFIG_PER_VMA_LOCKs
> * Trim some speculation out of the changelog
> ---
>
> b/arch/arm/Kconfig | 1
> b/arch/arm64/Kconfig | 1
> b/arch/loongarch/Kconfig | 1
> b/arch/powerpc/platforms/powernv/Kconfig | 1
> b/arch/powerpc/platforms/pseries/Kconfig | 1
> b/arch/riscv/Kconfig | 1
> b/arch/s390/Kconfig | 1
> b/arch/x86/Kconfig | 2 -
> b/fs/proc/internal.h | 2 -
> b/fs/proc/task_mmu.c | 51 ----------------------------
> b/include/linux/mm.h | 12 ------
> b/include/linux/mm_types.h | 7 ---
> b/include/linux/mmap_lock.h | 48 ---------------------------
> b/kernel/bpf/task_iter.c | 5 --
> b/kernel/fork.c | 2 -
> b/mm/Kconfig | 13 -------
> b/mm/Kconfig.debug | 1
> b/mm/debug.c | 4 --
> b/mm/init-mm.c | 2 -
> b/mm/memory.c | 2 -
> b/mm/mmap_lock.c | 24 -------------
> b/mm/pagewalk.c | 2 -
> b/mm/rmap.c | 2 -
> b/mm/userfaultfd.c | 55 -------------------------------
> b/rust/kernel/mm.rs | 7 ---
> b/tools/testing/vma/include/dup.h | 4 --
> b/tools/testing/vma/vma_internal.h | 1
> 27 files changed, 1 insertion(+), 252 deletions(-)
>
> diff -puN arch/arm64/Kconfig~unconditional-vma-locks arch/arm64/Kconfig
> --- a/arch/arm64/Kconfig~unconditional-vma-locks 2026-06-10 15:57:53.491348630 -0700
> +++ b/arch/arm64/Kconfig 2026-06-10 15:57:54.069369179 -0700
> @@ -80,7 +80,6 @@ config ARM64
> select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
> select ARCH_SUPPORTS_NUMA_BALANCING
> select ARCH_SUPPORTS_PAGE_TABLE_CHECK
> - select ARCH_SUPPORTS_PER_VMA_LOCK
> select ARCH_SUPPORTS_HUGE_PFNMAP if TRANSPARENT_HUGEPAGE
> select ARCH_SUPPORTS_RT
> select ARCH_SUPPORTS_SCHED_SMT
> diff -puN arch/arm/Kconfig~unconditional-vma-locks arch/arm/Kconfig
> --- a/arch/arm/Kconfig~unconditional-vma-locks 2026-06-10 15:57:53.499348914 -0700
> +++ b/arch/arm/Kconfig 2026-06-10 15:57:54.070369215 -0700
> @@ -41,7 +41,6 @@ config ARM
> select ARCH_SUPPORTS_ATOMIC_RMW
> select ARCH_SUPPORTS_CFI
> select ARCH_SUPPORTS_HUGETLBFS if ARM_LPAE
> - select ARCH_SUPPORTS_PER_VMA_LOCK
> select ARCH_SUPPORTS_RT
> select ARCH_USE_BUILTIN_BSWAP
> select ARCH_USE_CMPXCHG_LOCKREF
> diff -puN arch/loongarch/Kconfig~unconditional-vma-locks arch/loongarch/Kconfig
> --- a/arch/loongarch/Kconfig~unconditional-vma-locks 2026-06-10 15:57:53.542350439 -0700
> +++ b/arch/loongarch/Kconfig 2026-06-10 15:57:54.070369215 -0700
> @@ -68,7 +68,6 @@ config LOONGARCH
> select ARCH_SUPPORTS_LTO_CLANG_THIN
> select ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS
> select ARCH_SUPPORTS_NUMA_BALANCING if NUMA
> - select ARCH_SUPPORTS_PER_VMA_LOCK
> select ARCH_SUPPORTS_RT
> select ARCH_SUPPORTS_SCHED_SMT if SMP
> select ARCH_SUPPORTS_SCHED_MC if SMP
> diff -puN arch/powerpc/platforms/powernv/Kconfig~unconditional-vma-locks arch/powerpc/platforms/powernv/Kconfig
> --- a/arch/powerpc/platforms/powernv/Kconfig~unconditional-vma-locks 2026-06-10 15:57:53.544350510 -0700
> +++ b/arch/powerpc/platforms/powernv/Kconfig 2026-06-10 15:57:54.070369215 -0700
> @@ -17,7 +17,6 @@ config PPC_POWERNV
> select PPC_DOORBELL
> select MMU_NOTIFIER
> select FORCE_SMP
> - select ARCH_SUPPORTS_PER_VMA_LOCK
> select PPC_RADIX_BROADCAST_TLBIE if PPC_RADIX_MMU
> default y
>
> diff -puN arch/powerpc/platforms/pseries/Kconfig~unconditional-vma-locks arch/powerpc/platforms/pseries/Kconfig
> --- a/arch/powerpc/platforms/pseries/Kconfig~unconditional-vma-locks 2026-06-10 15:57:53.552350794 -0700
> +++ b/arch/powerpc/platforms/pseries/Kconfig 2026-06-10 15:57:54.070369215 -0700
> @@ -23,7 +23,6 @@ config PPC_PSERIES
> select HOTPLUG_CPU
> select FORCE_SMP
> select SWIOTLB
> - select ARCH_SUPPORTS_PER_VMA_LOCK
> select PPC_RADIX_BROADCAST_TLBIE if PPC_RADIX_MMU
> default y
>
> diff -puN arch/riscv/Kconfig~unconditional-vma-locks arch/riscv/Kconfig
> --- a/arch/riscv/Kconfig~unconditional-vma-locks 2026-06-10 15:57:53.559351043 -0700
> +++ b/arch/riscv/Kconfig 2026-06-10 15:57:54.070369215 -0700
> @@ -70,7 +70,6 @@ config RISCV
> select ARCH_SUPPORTS_LTO_CLANG_THIN
> select ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS if 64BIT && MMU
> select ARCH_SUPPORTS_PAGE_TABLE_CHECK if MMU
> - select ARCH_SUPPORTS_PER_VMA_LOCK if MMU
> select ARCH_SUPPORTS_RT
> select ARCH_SUPPORTS_SHADOW_CALL_STACK if HAVE_SHADOW_CALL_STACK
> select ARCH_SUPPORTS_SCHED_MC if SMP
> diff -puN arch/s390/Kconfig~unconditional-vma-locks arch/s390/Kconfig
> --- a/arch/s390/Kconfig~unconditional-vma-locks 2026-06-10 15:57:53.571351470 -0700
> +++ b/arch/s390/Kconfig 2026-06-10 15:57:54.071369250 -0700
> @@ -153,7 +153,6 @@ config S390
> select ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS
> select ARCH_SUPPORTS_NUMA_BALANCING
> select ARCH_SUPPORTS_PAGE_TABLE_CHECK
> - select ARCH_SUPPORTS_PER_VMA_LOCK
> select ARCH_USE_BUILTIN_BSWAP
> select ARCH_USE_CMPXCHG_LOCKREF
> select ARCH_USE_SYM_ANNOTATIONS
> diff -puN arch/x86/Kconfig~unconditional-vma-locks arch/x86/Kconfig
> --- a/arch/x86/Kconfig~unconditional-vma-locks 2026-06-10 15:57:53.577351684 -0700
> +++ b/arch/x86/Kconfig 2026-06-10 15:57:54.071369250 -0700
> @@ -27,7 +27,6 @@ config X86_64
> select ARCH_HAS_GIGANTIC_PAGE
> select ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS
> select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
> - select ARCH_SUPPORTS_PER_VMA_LOCK
> select ARCH_SUPPORTS_HUGE_PFNMAP if TRANSPARENT_HUGEPAGE
> select HAVE_ARCH_SOFT_DIRTY
> select MODULES_USE_ELF_RELA
> @@ -1885,7 +1884,6 @@ config X86_USER_SHADOW_STACK
> bool "X86 userspace shadow stack"
> depends on AS_WRUSS
> depends on X86_64
> - depends on PER_VMA_LOCK
> select ARCH_USES_HIGH_VMA_FLAGS
> select ARCH_HAS_USER_SHADOW_STACK
> select X86_CET
> diff -puN fs/proc/internal.h~unconditional-vma-locks fs/proc/internal.h
> --- a/fs/proc/internal.h~unconditional-vma-locks 2026-06-10 15:57:53.579351755 -0700
> +++ b/fs/proc/internal.h 2026-06-10 15:57:54.071369250 -0700
> @@ -382,10 +382,8 @@ struct mem_size_stats;
>
> struct proc_maps_locking_ctx {
> struct mm_struct *mm;
> -#ifdef CONFIG_PER_VMA_LOCK
> bool mmap_locked;
> struct vm_area_struct *locked_vma;
> -#endif
> };
>
> struct proc_maps_private {
> diff -puN fs/proc/task_mmu.c~unconditional-vma-locks fs/proc/task_mmu.c
> --- a/fs/proc/task_mmu.c~unconditional-vma-locks 2026-06-10 15:57:53.594352288 -0700
> +++ b/fs/proc/task_mmu.c 2026-06-10 15:57:54.072369286 -0700
> @@ -130,8 +130,6 @@ static void release_task_mempolicy(struc
> }
> #endif
>
> -#ifdef CONFIG_PER_VMA_LOCK
> -
A bunch of these helpers can be removed too but I'll do that cleanup
as a followup. Let's keep this one simple.
> static void reset_lock_ctx(struct proc_maps_locking_ctx *lock_ctx)
> {
> lock_ctx->locked_vma = NULL;
> @@ -213,33 +211,6 @@ static inline bool fallback_to_mmap_lock
> return true;
> }
>
> -#else /* CONFIG_PER_VMA_LOCK */
> -
> -static inline bool lock_vma_range(struct seq_file *m,
> - struct proc_maps_locking_ctx *lock_ctx)
> -{
> - return mmap_read_lock_killable(lock_ctx->mm) == 0;
> -}
> -
> -static inline void unlock_vma_range(struct proc_maps_locking_ctx *lock_ctx)
> -{
> - mmap_read_unlock(lock_ctx->mm);
> -}
> -
> -static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv,
> - loff_t last_pos)
> -{
> - return vma_next(&priv->iter);
> -}
> -
> -static inline bool fallback_to_mmap_lock(struct proc_maps_private *priv,
> - loff_t pos)
> -{
> - return false;
> -}
> -
> -#endif /* CONFIG_PER_VMA_LOCK */
> -
> static struct vm_area_struct *proc_get_vma(struct seq_file *m, loff_t *ppos)
> {
> struct proc_maps_private *priv = m->private;
> @@ -527,8 +498,6 @@ static int pid_maps_open(struct inode *i
> PROCMAP_QUERY_VMA_FLAGS \
> )
>
> -#ifdef CONFIG_PER_VMA_LOCK
> -
> static int query_vma_setup(struct proc_maps_locking_ctx *lock_ctx)
> {
> reset_lock_ctx(lock_ctx);
> @@ -581,26 +550,6 @@ static struct vm_area_struct *query_vma_
> return vma;
> }
>
> -#else /* CONFIG_PER_VMA_LOCK */
> -
> -static int query_vma_setup(struct proc_maps_locking_ctx *lock_ctx)
> -{
> - return mmap_read_lock_killable(lock_ctx->mm);
> -}
> -
> -static void query_vma_teardown(struct proc_maps_locking_ctx *lock_ctx)
> -{
> - mmap_read_unlock(lock_ctx->mm);
> -}
> -
> -static struct vm_area_struct *query_vma_find_by_addr(struct proc_maps_locking_ctx *lock_ctx,
> - unsigned long addr)
> -{
> - return find_vma(lock_ctx->mm, addr);
> -}
> -
> -#endif /* CONFIG_PER_VMA_LOCK */
> -
> static struct vm_area_struct *query_matching_vma(struct proc_maps_locking_ctx *lock_ctx,
> unsigned long addr, u32 flags)
> {
> diff -puN include/linux/mmap_lock.h~unconditional-vma-locks include/linux/mmap_lock.h
> --- a/include/linux/mmap_lock.h~unconditional-vma-locks 2026-06-10 15:57:53.599352466 -0700
> +++ b/include/linux/mmap_lock.h 2026-06-10 15:57:54.072369286 -0700
> @@ -76,8 +76,6 @@ static inline void mmap_assert_write_loc
> rwsem_assert_held_write(&mm->mmap_lock);
> }
>
> -#ifdef CONFIG_PER_VMA_LOCK
> -
> #ifdef CONFIG_LOCKDEP
> #define __vma_lockdep_map(vma) (&vma->vmlock_dep_map)
> #else
> @@ -484,52 +482,6 @@ struct vm_area_struct *lock_next_vma(str
> struct vma_iterator *iter,
> unsigned long address);
>
> -#else /* CONFIG_PER_VMA_LOCK */
> -
> -static inline void mm_lock_seqcount_init(struct mm_struct *mm) {}
> -static inline void mm_lock_seqcount_begin(struct mm_struct *mm) {}
> -static inline void mm_lock_seqcount_end(struct mm_struct *mm) {}
> -
> -static inline bool mmap_lock_speculate_try_begin(struct mm_struct *mm, unsigned int *seq)
> -{
> - return false;
> -}
> -
> -static inline bool mmap_lock_speculate_retry(struct mm_struct *mm, unsigned int seq)
> -{
> - return true;
> -}
> -static inline void vma_lock_init(struct vm_area_struct *vma, bool reset_refcnt) {}
> -static inline void vma_end_read(struct vm_area_struct *vma) {}
> -static inline void vma_start_write(struct vm_area_struct *vma) {}
> -static inline __must_check
> -int vma_start_write_killable(struct vm_area_struct *vma) { return 0; }
> -static inline void vma_assert_write_locked(struct vm_area_struct *vma)
> - { mmap_assert_write_locked(vma->vm_mm); }
> -static inline void vma_assert_attached(struct vm_area_struct *vma) {}
> -static inline void vma_assert_detached(struct vm_area_struct *vma) {}
> -static inline void vma_mark_attached(struct vm_area_struct *vma) {}
> -static inline void vma_mark_detached(struct vm_area_struct *vma) {}
> -
> -static inline struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm,
> - unsigned long address)
> -{
> - return NULL;
> -}
> -
> -static inline void vma_assert_locked(struct vm_area_struct *vma)
> -{
> - mmap_assert_locked(vma->vm_mm);
> -}
> -
> -static inline void vma_assert_stabilised(struct vm_area_struct *vma)
> -{
> - /* If no VMA locks, then either mmap lock suffices to stabilise. */
> - mmap_assert_locked(vma->vm_mm);
> -}
> -
> -#endif /* CONFIG_PER_VMA_LOCK */
> -
> static inline void mmap_write_lock(struct mm_struct *mm)
> {
> __mmap_lock_trace_start_locking(mm, true);
> diff -puN include/linux/mm.h~unconditional-vma-locks include/linux/mm.h
> --- a/include/linux/mm.h~unconditional-vma-locks 2026-06-10 15:57:53.745357660 -0700
> +++ b/include/linux/mm.h 2026-06-10 15:57:54.073369321 -0700
> @@ -890,7 +890,6 @@ static inline void vma_numab_state_free(
> * These must be here rather than mmap_lock.h as dependent on vm_fault type,
> * declared in this header.
> */
> -#ifdef CONFIG_PER_VMA_LOCK
> static inline void release_fault_lock(struct vm_fault *vmf)
> {
> if (vmf->flags & FAULT_FLAG_VMA_LOCK)
> @@ -906,17 +905,6 @@ static inline void assert_fault_locked(c
> else
> mmap_assert_locked(vmf->vma->vm_mm);
> }
> -#else
> -static inline void release_fault_lock(struct vm_fault *vmf)
> -{
> - mmap_read_unlock(vmf->vma->vm_mm);
> -}
> -
> -static inline void assert_fault_locked(const struct vm_fault *vmf)
> -{
> - mmap_assert_locked(vmf->vma->vm_mm);
> -}
> -#endif /* CONFIG_PER_VMA_LOCK */
>
> static inline bool mm_flags_test(int flag, const struct mm_struct *mm)
> {
> diff -puN include/linux/mm_types.h~unconditional-vma-locks include/linux/mm_types.h
> --- a/include/linux/mm_types.h~unconditional-vma-locks 2026-06-10 15:57:53.763358300 -0700
> +++ b/include/linux/mm_types.h 2026-06-10 15:57:54.074369357 -0700
> @@ -959,7 +959,6 @@ struct vm_area_struct {
> vma_flags_t flags;
> };
>
> -#ifdef CONFIG_PER_VMA_LOCK
> /*
> * Can only be written (using WRITE_ONCE()) while holding both:
> * - mmap_lock (in write mode)
> @@ -975,7 +974,7 @@ struct vm_area_struct {
> * slowpath.
> */
> unsigned int vm_lock_seq;
> -#endif
> +
> /*
> * A file's MAP_PRIVATE vma can be in both i_mmap tree and anon_vma
> * list, after a COW of one of the file pages. A MAP_SHARED vma
> @@ -1007,7 +1006,6 @@ struct vm_area_struct {
> #ifdef CONFIG_NUMA_BALANCING
> struct vma_numab_state *numab_state; /* NUMA Balancing state */
> #endif
> -#ifdef CONFIG_PER_VMA_LOCK
> /*
> * Used to keep track of firstly, whether the VMA is attached, secondly,
> * if attached, how many read locks are taken, and thirdly, if the
> @@ -1050,7 +1048,6 @@ struct vm_area_struct {
> #ifdef CONFIG_DEBUG_LOCK_ALLOC
> struct lockdep_map vmlock_dep_map;
> #endif
> -#endif
> /*
> * For areas with an address space and backing store,
> * linkage into the address_space->i_mmap interval tree.
> @@ -1249,7 +1246,6 @@ struct mm_struct {
> * init_mm.mmlist, and are protected
> * by mmlist_lock
> */
> -#ifdef CONFIG_PER_VMA_LOCK
> struct rcuwait vma_writer_wait;
> /*
> * This field has lock-like semantics, meaning it is sometimes
> @@ -1269,7 +1265,6 @@ struct mm_struct {
> * mmap_lock.
> */
> seqcount_t mm_lock_seq;
> -#endif
> #ifdef CONFIG_FUTEX_PRIVATE_HASH
> struct mutex futex_hash_lock;
> struct futex_private_hash __rcu *futex_phash;
> diff -puN kernel/bpf/task_iter.c~unconditional-vma-locks kernel/bpf/task_iter.c
> --- a/kernel/bpf/task_iter.c~unconditional-vma-locks 2026-06-10 15:57:53.773358655 -0700
> +++ b/kernel/bpf/task_iter.c 2026-06-10 15:57:54.074369357 -0700
> @@ -835,11 +835,6 @@ __bpf_kfunc int bpf_iter_task_vma_new(st
> BUILD_BUG_ON(sizeof(struct bpf_iter_task_vma_kern) != sizeof(struct bpf_iter_task_vma));
> BUILD_BUG_ON(__alignof__(struct bpf_iter_task_vma_kern) != __alignof__(struct bpf_iter_task_vma));
>
> - if (!IS_ENABLED(CONFIG_PER_VMA_LOCK)) {
> - kit->data = NULL;
> - return -EOPNOTSUPP;
> - }
> -
> /*
> * Reject irqs-disabled contexts including NMI. Operations used
> * by _next() and _destroy() (vma_end_read, fput, bpf_iter_mmput_async)
> diff -puN kernel/fork.c~unconditional-vma-locks kernel/fork.c
> --- a/kernel/fork.c~unconditional-vma-locks 2026-06-10 15:57:53.783359011 -0700
> +++ b/kernel/fork.c 2026-06-10 15:57:54.074369357 -0700
> @@ -1067,9 +1067,7 @@ static void mmap_init_lock(struct mm_str
> {
> init_rwsem(&mm->mmap_lock);
> mm_lock_seqcount_init(mm);
> -#ifdef CONFIG_PER_VMA_LOCK
> rcuwait_init(&mm->vma_writer_wait);
> -#endif
> }
>
> static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
> diff -puN mm/debug.c~unconditional-vma-locks mm/debug.c
> --- a/mm/debug.c~unconditional-vma-locks 2026-06-10 15:57:53.785359082 -0700
> +++ b/mm/debug.c 2026-06-10 15:57:54.075369392 -0700
> @@ -157,17 +157,13 @@ void dump_vma(const struct vm_area_struc
> pr_emerg("vma %px start %px end %px mm %px\n"
> "prot %lx anon_vma %px vm_ops %px\n"
> "pgoff %lx file %px private_data %px\n"
> -#ifdef CONFIG_PER_VMA_LOCK
> "refcnt %x\n"
> -#endif
> "flags: %#lx(%pGv)\n",
> vma, (void *)vma->vm_start, (void *)vma->vm_end, vma->vm_mm,
> (unsigned long)pgprot_val(vma->vm_page_prot),
> vma->anon_vma, vma->vm_ops, vma->vm_pgoff,
> vma->vm_file, vma->vm_private_data,
> -#ifdef CONFIG_PER_VMA_LOCK
> refcount_read(&vma->vm_refcnt),
> -#endif
> vma->vm_flags, &vma->vm_flags);
> }
> EXPORT_SYMBOL(dump_vma);
> diff -puN mm/init-mm.c~unconditional-vma-locks mm/init-mm.c
> --- a/mm/init-mm.c~unconditional-vma-locks 2026-06-10 15:57:53.808359899 -0700
> +++ b/mm/init-mm.c 2026-06-10 15:57:54.075369392 -0700
> @@ -39,10 +39,8 @@ struct mm_struct init_mm = {
> .page_table_lock = __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock),
> .arg_lock = __SPIN_LOCK_UNLOCKED(init_mm.arg_lock),
> .mmlist = LIST_HEAD_INIT(init_mm.mmlist),
> -#ifdef CONFIG_PER_VMA_LOCK
> .vma_writer_wait = __RCUWAIT_INITIALIZER(init_mm.vma_writer_wait),
> .mm_lock_seq = SEQCNT_ZERO(init_mm.mm_lock_seq),
> -#endif
> .user_ns = &init_user_ns,
> #ifdef CONFIG_SCHED_MM_CID
> .mm_cid.lock = __RAW_SPIN_LOCK_UNLOCKED(init_mm.mm_cid.lock),
> diff -puN mm/Kconfig~unconditional-vma-locks mm/Kconfig
> --- a/mm/Kconfig~unconditional-vma-locks 2026-06-10 15:57:53.816360183 -0700
> +++ b/mm/Kconfig 2026-06-10 15:57:54.075369392 -0700
> @@ -1394,19 +1394,6 @@ config LRU_GEN_STATS
> config LRU_GEN_WALKS_MMU
> def_bool y
> depends on LRU_GEN && ARCH_HAS_HW_PTE_YOUNG
> -# }
> -
> -config ARCH_SUPPORTS_PER_VMA_LOCK
> - def_bool n
> -
> -config PER_VMA_LOCK
> - def_bool y
> - depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP
> - help
> - Allow per-vma locking during page fault handling.
> -
> - This feature allows locking each virtual memory area separately when
> - handling page faults instead of taking mmap_lock.
>
> config LOCK_MM_AND_FIND_VMA
> bool
> diff -puN mm/Kconfig.debug~unconditional-vma-locks mm/Kconfig.debug
> --- a/mm/Kconfig.debug~unconditional-vma-locks 2026-06-10 15:57:53.820360326 -0700
> +++ b/mm/Kconfig.debug 2026-06-10 15:57:54.075369392 -0700
> @@ -310,7 +310,6 @@ config DEBUG_KMEMLEAK_VERBOSE
>
> config PER_VMA_LOCK_STATS
> bool "Statistics for per-vma locks"
> - depends on PER_VMA_LOCK
> help
> Say Y here to enable success, retry and failure counters of page
> faults handled under protection of per-vma locks. When enabled, the
> diff -puN mm/memory.c~unconditional-vma-locks mm/memory.c
> --- a/mm/memory.c~unconditional-vma-locks 2026-06-10 15:57:53.830360681 -0700
> +++ b/mm/memory.c 2026-06-10 15:57:54.076369428 -0700
> @@ -6659,7 +6659,6 @@ static vm_fault_t sanitize_fault_flags(s
> !is_cow_mapping(vma->vm_flags)))
> return VM_FAULT_SIGSEGV;
> }
> -#ifdef CONFIG_PER_VMA_LOCK
> /*
> * Per-VMA locks can't be used with FAULT_FLAG_RETRY_NOWAIT because of
> * the assumption that lock is dropped on VM_FAULT_RETRY.
> @@ -6668,7 +6667,6 @@ static vm_fault_t sanitize_fault_flags(s
> (FAULT_FLAG_VMA_LOCK | FAULT_FLAG_RETRY_NOWAIT)) ==
> (FAULT_FLAG_VMA_LOCK | FAULT_FLAG_RETRY_NOWAIT)))
> return VM_FAULT_SIGSEGV;
> -#endif
>
> return 0;
> }
> diff -puN mm/mmap_lock.c~unconditional-vma-locks mm/mmap_lock.c
> --- a/mm/mmap_lock.c~unconditional-vma-locks 2026-06-10 15:57:53.834360824 -0700
> +++ b/mm/mmap_lock.c 2026-06-10 15:57:54.077369463 -0700
> @@ -43,9 +43,6 @@ void __mmap_lock_do_trace_released(struc
> EXPORT_SYMBOL(__mmap_lock_do_trace_released);
> #endif /* CONFIG_TRACING */
>
> -#ifdef CONFIG_MMU
> -#ifdef CONFIG_PER_VMA_LOCK
> -
> /* State shared across __vma_[start, end]_exclude_readers. */
> struct vma_exclude_readers_state {
> /* Input parameters. */
> @@ -431,7 +428,6 @@ fallback:
>
> return vma;
> }
> -#endif /* CONFIG_PER_VMA_LOCK */
>
> #ifdef CONFIG_LOCK_MM_AND_FIND_VMA
> #include <linux/extable.h>
> @@ -548,23 +544,3 @@ fail:
> return NULL;
> }
> #endif /* CONFIG_LOCK_MM_AND_FIND_VMA */
> -
> -#else /* CONFIG_MMU */
> -
> -/*
> - * At least xtensa ends up having protection faults even with no
> - * MMU.. No stack expansion, at least.
> - */
> -struct vm_area_struct *lock_mm_and_find_vma(struct mm_struct *mm,
> - unsigned long addr, struct pt_regs *regs)
> -{
> - struct vm_area_struct *vma;
> -
> - mmap_read_lock(mm);
> - vma = vma_lookup(mm, addr);
> - if (!vma)
> - mmap_read_unlock(mm);
> - return vma;
> -}
Might this removal break CONFIG_MMU=n && CONFIG_LOCK_MM_AND_FIND_VMA=n case?
> -
> -#endif /* CONFIG_MMU */
> diff -puN mm/pagewalk.c~unconditional-vma-locks mm/pagewalk.c
> --- a/mm/pagewalk.c~unconditional-vma-locks 2026-06-10 15:57:53.851361429 -0700
> +++ b/mm/pagewalk.c 2026-06-10 15:57:54.077369463 -0700
> @@ -446,7 +446,6 @@ static inline void process_mm_walk_lock(
> static inline void process_vma_walk_lock(struct vm_area_struct *vma,
> enum page_walk_lock walk_lock)
> {
> -#ifdef CONFIG_PER_VMA_LOCK
> switch (walk_lock) {
> case PGWALK_WRLOCK:
> vma_start_write(vma);
> @@ -461,7 +460,6 @@ static inline void process_vma_walk_lock
> /* PGWALK_RDLOCK is handled by process_mm_walk_lock */
> break;
> }
> -#endif
> }
>
> /*
> diff -puN mm/rmap.c~unconditional-vma-locks mm/rmap.c
> --- a/mm/rmap.c~unconditional-vma-locks 2026-06-10 15:57:54.018367366 -0700
> +++ b/mm/rmap.c 2026-06-10 15:57:54.077369463 -0700
> @@ -260,11 +260,9 @@ static void check_anon_vma_clone(struct
> /* For the anon_vma to be compatible, it can only be singular. */
> VM_WARN_ON_ONCE(operation == VMA_OP_MERGE_UNFAULTED &&
> !list_is_singular(&src->anon_vma_chain));
> -#ifdef CONFIG_PER_VMA_LOCK
> /* Only merging an unfaulted VMA leaves the destination attached. */
> VM_WARN_ON_ONCE(operation != VMA_OP_MERGE_UNFAULTED &&
> vma_is_attached(dst));
> -#endif
> }
>
> static void maybe_reuse_anon_vma(struct vm_area_struct *dst,
> diff -puN mm/userfaultfd.c~unconditional-vma-locks mm/userfaultfd.c
> --- a/mm/userfaultfd.c~unconditional-vma-locks 2026-06-10 15:57:54.049368468 -0700
> +++ b/mm/userfaultfd.c 2026-06-10 15:57:54.078369499 -0700
> @@ -104,7 +104,6 @@ struct vm_area_struct *find_vma_and_prep
> return vma;
> }
>
> -#ifdef CONFIG_PER_VMA_LOCK
> /*
> * uffd_lock_vma() - Lookup and lock vma corresponding to @address.
> * @mm: mm to search vma in.
> @@ -164,34 +163,6 @@ static void uffd_mfill_unlock(struct vm_
> vma_end_read(vma);
> }
>
> -#else
> -
> -static struct vm_area_struct *uffd_mfill_lock(struct mm_struct *dst_mm,
> - unsigned long dst_start,
> - unsigned long len)
> -{
> - struct vm_area_struct *dst_vma;
> -
> - mmap_read_lock(dst_mm);
> - dst_vma = find_vma_and_prepare_anon(dst_mm, dst_start);
> - if (IS_ERR(dst_vma))
> - goto out_unlock;
> -
> - if (validate_dst_vma(dst_vma, dst_start + len))
> - return dst_vma;
> -
> - dst_vma = ERR_PTR(-ENOENT);
> -out_unlock:
> - mmap_read_unlock(dst_mm);
> - return dst_vma;
> -}
> -
> -static void uffd_mfill_unlock(struct vm_area_struct *vma)
> -{
> - mmap_read_unlock(vma->vm_mm);
> -}
> -#endif
> -
> static void mfill_put_vma(struct mfill_state *state)
> {
> if (!state->vma)
> @@ -1672,7 +1643,6 @@ out_success:
> return 0;
> }
>
> -#ifdef CONFIG_PER_VMA_LOCK
> static int uffd_move_lock(struct mm_struct *mm,
> unsigned long dst_start,
> unsigned long src_start,
> @@ -1747,31 +1717,6 @@ static void uffd_move_unlock(struct vm_a
> vma_end_read(dst_vma);
> }
>
> -#else
> -
> -static int uffd_move_lock(struct mm_struct *mm,
> - unsigned long dst_start,
> - unsigned long src_start,
> - struct vm_area_struct **dst_vmap,
> - struct vm_area_struct **src_vmap)
> -{
> - int err;
> -
> - mmap_read_lock(mm);
> - err = find_vmas_mm_locked(mm, dst_start, src_start, dst_vmap, src_vmap);
> - if (err)
> - mmap_read_unlock(mm);
> - return err;
> -}
> -
> -static void uffd_move_unlock(struct vm_area_struct *dst_vma,
> - struct vm_area_struct *src_vma)
> -{
> - mmap_assert_locked(src_vma->vm_mm);
> - mmap_read_unlock(dst_vma->vm_mm);
> -}
> -#endif
> -
> /**
> * move_pages - move arbitrary anonymous pages of an existing vma
> * @ctx: pointer to the userfaultfd context
> diff -puN rust/kernel/mm.rs~unconditional-vma-locks rust/kernel/mm.rs
> --- a/rust/kernel/mm.rs~unconditional-vma-locks 2026-06-10 15:57:54.051368539 -0700
> +++ b/rust/kernel/mm.rs 2026-06-10 15:57:54.078369499 -0700
> @@ -174,7 +174,6 @@ impl MmWithUser {
> /// When per-vma locks are disabled, this always returns `None`.
> #[inline]
> pub fn lock_vma_under_rcu(&self, vma_addr: usize) -> Option<VmaReadGuard<'_>> {
> - #[cfg(CONFIG_PER_VMA_LOCK)]
> {
> // SAFETY: Calling `bindings::lock_vma_under_rcu` is always okay given an mm where
> // `mm_users` is non-zero.
> @@ -188,12 +187,6 @@ impl MmWithUser {
> });
> }
> }
> -
> - // Silence warnings about unused variables.
> - #[cfg(not(CONFIG_PER_VMA_LOCK))]
> - let _ = vma_addr;
> -
> - None
> }
>
> /// Lock the mmap read lock.
> diff -puN tools/testing/vma/include/dup.h~unconditional-vma-locks tools/testing/vma/include/dup.h
> --- a/tools/testing/vma/include/dup.h~unconditional-vma-locks 2026-06-10 15:57:54.064369001 -0700
> +++ b/tools/testing/vma/include/dup.h 2026-06-10 15:57:54.078369499 -0700
> @@ -569,7 +569,6 @@ struct vm_area_struct {
> vma_flags_t flags;
> };
>
> -#ifdef CONFIG_PER_VMA_LOCK
> /*
> * Can only be written (using WRITE_ONCE()) while holding both:
> * - mmap_lock (in write mode)
> @@ -585,7 +584,6 @@ struct vm_area_struct {
> * slowpath.
> */
> unsigned int vm_lock_seq;
> -#endif
>
> /*
> * A file's MAP_PRIVATE vma can be in both i_mmap tree and anon_vma
> @@ -618,10 +616,8 @@ struct vm_area_struct {
> #ifdef CONFIG_NUMA_BALANCING
> struct vma_numab_state *numab_state; /* NUMA Balancing state */
> #endif
> -#ifdef CONFIG_PER_VMA_LOCK
> /* Unstable RCU readers are allowed to read this. */
> refcount_t vm_refcnt;
> -#endif
> /*
> * For areas with an address space and backing store,
> * linkage into the address_space->i_mmap interval tree.
> diff -puN tools/testing/vma/vma_internal.h~unconditional-vma-locks tools/testing/vma/vma_internal.h
> --- a/tools/testing/vma/vma_internal.h~unconditional-vma-locks 2026-06-10 15:57:54.066369072 -0700
> +++ b/tools/testing/vma/vma_internal.h 2026-06-10 15:57:54.078369499 -0700
> @@ -15,7 +15,6 @@
> #include <stdlib.h>
>
> #define CONFIG_MMU
> -#define CONFIG_PER_VMA_LOCK
>
> #ifdef __CONCAT
> #undef __CONCAT
> _