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 49D2D3DB626; Fri, 14 Aug 2026 19:03:36 +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=1786734218; cv=none; b=KYKIoznWTmWedZUZej9fQXJ3HjNhkpV5o+TSllQlz5BctIzNiXMGumAZNUnv578PCTAK6hWZBETw1rnB8xhCrcfJSoYWKJ1hO1iW4BT+5QnDS+YwTtqDiVS6kBRg33GDcxJJgkkScOgfZwg0Me5qIQy7ghh0/eZpAj5yDnaIeSg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786734218; c=relaxed/simple; bh=DnDHsbJVA9DXeOqU7fwm7bXhgoe/ZcQBtFFEHMaB1QI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=hVUUTeOgM8MX8FIeCy+NVqJ6/1LoOVcU22Bb0LP2IJwcbw/2LShMHBXnnBFkQDfkE/SFxQUjWAJNfcL/5MSmpamSMFWwDuUEmALmg2zl4Iw1kYO38gOSMriGfM3qyfVZQwBU6cSexCVfVrGIWl83yKp8oRROYVKS+NuxTyZqqN8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=m/le2I6p; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="m/le2I6p" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 766BB1F000E9; Fri, 14 Aug 2026 19:03:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786734215; bh=bWPWJC9u7mp7jO+L3KN9SOtYgYUiZVK74k5uGEGtCPM=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=m/le2I6plISuHhoNz5BB8qUIKu18xxUmyn4RuWShIxg4MDRq3XXmFAl6C4iYZ2tGR sgYNHCVOik8e2T3gT4Ke6Wqa8i6rQ5HnlhI9jUuYLvaapJ4Vv5elBEOTNDc1+vG7EP mLbo3MGogw1qOOIeXdbEyYXWmZeM4AD+/akwzFy5y+XogfOhHloVDYY/+FE4SPVvhl /dVRnF2Ih/H+db7Grv0K0hEChsLbX7st6eSYZwZXL2LvhvJGhqI/otAgfEVIAVuzPq Le4MHJJD//QxD4fqoIWzcSFKIIJMoBoMEvs+XrxtF3aw0RVuAKxt8j4qSywHN2TwL3 I0Nruk0l18PEg== Date: Fri, 14 Aug 2026 20:03:15 +0100 From: "Lorenzo Stoakes (ARM)" To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, dave.hansen@linux.intel.com, Liam.Howlett@oracle.com, david@redhat.com, willy@infradead.org, shakeel.butt@linux.dev, vbabka@kernel.org, jannh@google.com, aliceryhl@google.com, arve@android.com, cmllamas@google.com, christian@brauner.io, tkjos@android.com, dsahern@kernel.org, davem@davemloft.net, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org Subject: Re: [PATCH v6 1/5] mm: Make per-VMA locks available universally Message-ID: References: <20260813193433.3318288-1-surenb@google.com> <20260813193433.3318288-2-surenb@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260813193433.3318288-2-surenb@google.com> On Thu, Aug 13, 2026 at 12:34:29PM -0700, Suren Baghdasaryan wrote: > From: Dave Hansen > > 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. > > 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. > > == Considerations for NOMMU config == > > NOMMU systems do not write-lock VMAs, therefore read-locking a VMA > would always succeed unless VMA is detached. Therefore for NOMMU > config we make vma_mark_attached() a NOOP, which keeps VMAs always in > detached state. This causes VMA read-locking to always fail and the > caller falls back to locking mmap_lock. > > The following functions will have a different implementation in NOMMU > config: > > - vma_mark_attached(), vma_mark_detached() are made NOOPs, keeping VMAs > always in a detached state and preventing assertions and refcount > underflows; > > - vma_start_write(), vma_start_write_killable() are made NOOPs to avoid > warnings in __vma_start_write() due to VMAs being detached. > These functions are not used in NOMMU code but __vma_start_write() > is an exported function, therefore might be used by drivers. > > - vma_assert_attached() is made NOOP because it's reachable from NOMMU > code via split_vma()->vma_iter_store_new()->vma_iter_store_overwrite(); > > - vma_assert_write_locked() is asserting vma->vm_mm is write-locked, as > was done before this change; > > - vma_assert_locked() is asserting vma->vm_mm is locked, as was done > before this change; > > The following functions work for both MMU and NOMMU configs: > > - vma_lock_init() performs the same initialization as for MMU config; > > - mm_lock_seqcount_init(), mm_lock_seqcount_begin(), mm_lock_seqcount_end() > are called from mmap_write_{lock|unlock} and update mm_lock_seq correctly. > > - mmap_lock_speculate_try_begin(), mmap_lock_speculate_retry() work as is > because mm_lock_seq is updated correctly; > > - vma_start_read(), vma_start_read_locked() will always fail because VMAs > are always detached; > > - vma_end_read() will never be called because vma_start_read() never > succeeds; > > - vma_is_attached() always return false because VMAs are always detached; > > - vma_assert_detached() will never trigger because VMAs are never attached; > > - vma_start_read_locked() always return false because VMAs are always > detached; > > - lock_vma_under_rcu() will be safe as the attempted read lock will bail; > > Changes in the following files are not affecting NOMMU config: > > task_mmu.c - not compiled when CONFIG_MMU=n; > pagewalk.c - not compiled when CONFIG_MMU=n; > userfaultfd.c - not compiled when CONFIG_MMU=n (CONFIG_USERFAULTFD depends > on CONFIG_MMU); > > The following changes in the BPF code are made to keep NOMMU config > working like before: > > stack_map_lock_vma() - keeps mmap_lock in NOMMU config; > bpf_iter_task_vma_new() - bails out in NOMMU config; > > Signed-off-by: Dave Hansen > Cc: Suren Baghdasaryan > Cc: Andrew Morton > Cc: Liam R. Howlett > Cc: Lorenzo Stoakes > Cc: Vlastimil Babka > Cc: Shakeel Butt > Cc: linux-mm@kvack.org > Cc: Greg Kroah-Hartman > Cc: Arve Hjønnevåg > Cc: Todd Kjos > Cc: Christian Brauner > Cc: Carlos Llamas > Cc: Alice Ryhl > Cc: David S. Miller > Cc: David Ahern > Cc: netdev@vger.kernel.org > Acked-by: Vlastimil Babka (SUSE) > Signed-off-by: Suren Baghdasaryan LGTM so: Reviewed-by: Lorenzo Stoakes (ARM) > --- > arch/arm/Kconfig | 1 - > arch/arm64/Kconfig | 1 - > arch/loongarch/Kconfig | 1 - > arch/powerpc/platforms/powernv/Kconfig | 1 - > arch/powerpc/platforms/pseries/Kconfig | 1 - > arch/riscv/Kconfig | 1 - > arch/s390/Kconfig | 1 - > arch/x86/Kconfig | 2 - > fs/proc/internal.h | 2 - > fs/proc/task_mmu.c | 93 -------------------------- > include/linux/mm.h | 12 ---- > include/linux/mm_types.h | 8 +-- > include/linux/mmap_lock.h | 75 +++++++-------------- > kernel/bpf/stackmap.c | 17 ++--- > kernel/bpf/task_iter.c | 2 +- > kernel/fork.c | 2 - > mm/Kconfig | 12 ---- > mm/Kconfig.debug | 1 - > mm/debug.c | 4 -- > mm/init-mm.c | 2 - > mm/memory.c | 2 - > mm/mmap_lock.c | 26 +------ > mm/pagewalk.c | 2 - > mm/rmap.c | 2 - > mm/userfaultfd.c | 55 --------------- > rust/kernel/mm.rs | 32 +++------ > tools/testing/vma/include/dup.h | 5 +- > tools/testing/vma/vma_internal.h | 1 - > 28 files changed, 48 insertions(+), 316 deletions(-) > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index 9187240a02db..f815209167cd 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -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 --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 11a9c534b7b4..21eb64b24a2c 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -81,7 +81,6 @@ config ARM64 > select ARCH_HAS_PTE_PROTNONE > 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 --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig > index e20acbe5fe7b..7741e39eca2b 100644 > --- a/arch/loongarch/Kconfig > +++ b/arch/loongarch/Kconfig > @@ -69,7 +69,6 @@ config LOONGARCH > select ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS > select ARCH_HAS_PTE_PROTNONE if 64BIT > 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 --git a/arch/powerpc/platforms/powernv/Kconfig b/arch/powerpc/platforms/powernv/Kconfig > index b5ad7c173ef0..dd8f6060fb7a 100644 > --- a/arch/powerpc/platforms/powernv/Kconfig > +++ b/arch/powerpc/platforms/powernv/Kconfig > @@ -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 --git a/arch/powerpc/platforms/pseries/Kconfig b/arch/powerpc/platforms/pseries/Kconfig > index 74910ce3a541..7d125e288f6e 100644 > --- a/arch/powerpc/platforms/pseries/Kconfig > +++ b/arch/powerpc/platforms/pseries/Kconfig > @@ -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 --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > index 7b9c373d82fa..faa85a031fe5 100644 > --- a/arch/riscv/Kconfig > +++ b/arch/riscv/Kconfig > @@ -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_HAS_PTE_PROTNONE if MMU > select ARCH_SUPPORTS_RT > select ARCH_SUPPORTS_SHADOW_CALL_STACK if HAVE_SHADOW_CALL_STACK > diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig > index ab8fccc2cc4e..d1274bca8c39 100644 > --- a/arch/s390/Kconfig > +++ b/arch/s390/Kconfig > @@ -151,7 +151,6 @@ config S390 > select ARCH_HAS_PTE_PROTNONE > 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 --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index fb298e219179..79479d29576f 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -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 > @@ -1846,7 +1845,6 @@ 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 --git a/fs/proc/internal.h b/fs/proc/internal.h > index b232e1098117..6713757da099 100644 > --- a/fs/proc/internal.h > +++ b/fs/proc/internal.h > @@ -385,10 +385,8 @@ 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 --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index 5c54aebe2118..e671b4fd8ded 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -130,8 +130,6 @@ static void release_task_mempolicy(struct proc_maps_private *priv) > } > #endif > > -#ifdef CONFIG_PER_VMA_LOCK > - > static inline int lock_ctx_mm(struct proc_maps_locking_ctx *lock_ctx) > { > int ret = mmap_read_lock_killable(lock_ctx->mm); > @@ -233,46 +231,6 @@ static inline void reacquire_rcu(struct proc_maps_private *priv) > vma_iter_set(&priv->iter, priv->lock_ctx.locked_vma->vm_end); > } > > -#else /* CONFIG_PER_VMA_LOCK */ > - > -static inline int lock_ctx_mm(struct proc_maps_locking_ctx *lock_ctx) > -{ > - return mmap_read_lock_killable(lock_ctx->mm); > -} > - > -static inline void unlock_ctx_mm(struct proc_maps_locking_ctx *lock_ctx) > -{ > - mmap_read_unlock(lock_ctx->mm); > -} > - > -static inline bool lock_vma_range(struct seq_file *m, > - struct proc_maps_locking_ctx *lock_ctx) > -{ > - return lock_ctx_mm(lock_ctx) == 0; > -} > - > -static inline void unlock_vma_range(struct proc_maps_locking_ctx *lock_ctx) > -{ > - unlock_ctx_mm(lock_ctx); > -} > - > -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; > -} > - > -static inline void drop_rcu(struct proc_maps_private *priv) {} > -static inline void reacquire_rcu(struct proc_maps_private *priv) {} > - > -#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; > @@ -560,8 +518,6 @@ static int pid_maps_open(struct inode *inode, struct file *file) > 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); > @@ -612,26 +568,6 @@ static struct vm_area_struct *query_vma_find_by_addr(struct proc_maps_locking_ct > 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) > { > @@ -1314,8 +1250,6 @@ static const struct mm_walk_ops smaps_shmem_walk_ops = { > .walk_lock = PGWALK_RDLOCK, > }; > > -#ifdef CONFIG_PER_VMA_LOCK > - > static const struct mm_walk_ops smaps_walk_vma_lock_ops = { > .pmd_entry = smaps_pte_range, > .hugetlb_entry = smaps_hugetlb_range, > @@ -1345,22 +1279,6 @@ get_smaps_shmem_walk_ops(struct proc_maps_private *priv) > return &smaps_shmem_walk_vma_lock_ops; > } > > -#else /* CONFIG_PER_VMA_LOCK */ > - > -static inline const struct mm_walk_ops * > -get_smaps_walk_ops(struct proc_maps_private *priv) > -{ > - return &smaps_walk_ops; > -} > - > -static inline const struct mm_walk_ops * > -get_smaps_shmem_walk_ops(struct proc_maps_private *priv) > -{ > - return &smaps_shmem_walk_ops; > -} > - > -#endif /* CONFIG_PER_VMA_LOCK */ > - > /* > * Gather mem stats from @vma with the indicated beginning > * address @start, and keep them in @mss. > @@ -3497,7 +3415,6 @@ static const struct mm_walk_ops show_numa_ops = { > .walk_lock = PGWALK_RDLOCK, > }; > > -#ifdef CONFIG_PER_VMA_LOCK > static const struct mm_walk_ops show_numa_vma_lock_ops = { > .hugetlb_entry = gather_hugetlb_stats, > .pmd_entry = gather_pte_stats, > @@ -3512,16 +3429,6 @@ get_show_numa_ops(struct proc_maps_private *priv) > return &show_numa_vma_lock_ops; > } > > -#else /* CONFIG_PER_VMA_LOCK */ > - > -static inline const struct mm_walk_ops * > -get_show_numa_ops(struct proc_maps_private *priv) > -{ > - return &show_numa_ops; > -} > - > -#endif /* CONFIG_PER_VMA_LOCK */ > - > /* > * Display pages allocated per node and memory policy via /proc. > */ > diff --git a/include/linux/mm.h b/include/linux/mm.h > index f940d20551d5..73a6244e1dd0 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -931,7 +931,6 @@ static inline void vma_numab_state_free(struct vm_area_struct *vma) {} > * 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) > @@ -947,17 +946,6 @@ static inline void assert_fault_locked(const struct vm_fault *vmf) > 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 --git a/include/linux/mm_types.h b/include/linux/mm_types.h > index 6d815f6440c9..5413bd10fff2 100644 > --- a/include/linux/mm_types.h > +++ b/include/linux/mm_types.h > @@ -950,7 +950,6 @@ 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) > @@ -966,7 +965,7 @@ struct vm_area_struct { > * slowpath. > */ > unsigned int vm_lock_seq; > -#endif > + > /* > * Low 32-bits of anonymous page offset. > * See vma_start_anon_pgoff() comment for details. > @@ -1003,7 +1002,6 @@ 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 > @@ -1046,7 +1044,6 @@ struct vm_area_struct { > #ifdef CONFIG_DEBUG_LOCK_ALLOC > struct lockdep_map vmlock_dep_map; > #endif > -#endif > #ifdef CONFIG_64BIT > /* > * High 32-bits of anonymous page offset. > @@ -1254,7 +1251,6 @@ 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 > @@ -1274,7 +1270,7 @@ struct mm_struct { > * mmap_lock. > */ > seqcount_t mm_lock_seq; > -#endif > + > struct futex_mm_data futex; > > unsigned long hiwater_rss; /* High-watermark of RSS usage */ > diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h > index 87f77e3da77f..db2dbf84943c 100644 > --- a/include/linux/mmap_lock.h > +++ b/include/linux/mmap_lock.h > @@ -76,8 +76,6 @@ static inline void mmap_assert_write_locked(const struct mm_struct *mm) > 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 > @@ -297,6 +295,9 @@ int __vma_start_write(struct vm_area_struct *vma, int state); > */ > static inline void vma_start_write(struct vm_area_struct *vma) > { > + if (!IS_ENABLED(CONFIG_MMU)) > + return; > + > if (__is_vma_write_locked(vma)) > return; > > @@ -319,6 +320,9 @@ 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) > { > + if (!IS_ENABLED(CONFIG_MMU)) > + return 0; > + > if (__is_vma_write_locked(vma)) > return 0; > > @@ -331,6 +335,11 @@ int vma_start_write_killable(struct vm_area_struct *vma) > */ > static inline void vma_assert_write_locked(struct vm_area_struct *vma) > { > + if (!IS_ENABLED(CONFIG_MMU)) { > + mmap_assert_write_locked(vma->vm_mm); > + return; > + } > + > VM_WARN_ON_ONCE_VMA(!__is_vma_write_locked(vma), vma); > } > > @@ -343,6 +352,11 @@ static inline void vma_assert_locked(struct vm_area_struct *vma) > { > unsigned int refcnt; > > + if (!IS_ENABLED(CONFIG_MMU)) { > + mmap_assert_locked(vma->vm_mm); > + return; > + } > + > if (IS_ENABLED(CONFIG_LOCKDEP)) { > if (!lock_is_held(__vma_lockdep_map(vma))) > vma_assert_write_locked(vma); > @@ -432,6 +446,9 @@ static inline bool vma_is_attached(struct vm_area_struct *vma) > */ > static inline void vma_assert_attached(struct vm_area_struct *vma) > { > + if (!IS_ENABLED(CONFIG_MMU)) > + return; > + > WARN_ON_ONCE(!vma_is_attached(vma)); > } > > @@ -442,6 +459,9 @@ static inline void vma_assert_detached(struct vm_area_struct *vma) > > static inline void vma_mark_attached(struct vm_area_struct *vma) > { > + if (!IS_ENABLED(CONFIG_MMU)) > + return; > + > vma_assert_write_locked(vma); > vma_assert_detached(vma); > refcount_set_release(&vma->vm_refcnt, 1); > @@ -451,6 +471,9 @@ void __vma_exclude_readers_for_detach(struct vm_area_struct *vma); > > static inline void vma_mark_detached(struct vm_area_struct *vma) > { > + if (!IS_ENABLED(CONFIG_MMU)) > + return; > + > vma_assert_write_locked(vma); > vma_assert_attached(vma); > > @@ -484,54 +507,6 @@ struct vm_area_struct *lock_next_vma(struct mm_struct *mm, > 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 bool vma_is_attached(struct vm_area_struct *vma) > - { return true; } > -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 vma_assert_can_modify(struct vm_area_struct *vma) > { > if (vma_is_attached(vma)) > diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c > index 41fe87d7302f..6bd6022b6b84 100644 > --- a/kernel/bpf/stackmap.c > +++ b/kernel/bpf/stackmap.c > @@ -272,13 +272,10 @@ struct stack_map_vma_lock { > /* > * Acquire a stable read-side reference on the VMA covering @ip. > * > - * With CONFIG_PER_VMA_LOCK=y this returns a VMA with its per-VMA read > - * lock held and mmap_lock dropped, so the caller may sleep. > - * > - * With CONFIG_PER_VMA_LOCK=n it returns a VMA with mmap_lock still > - * held; the caller must snapshot any fields it needs and pin vm_file > - * with get_file() before stack_map_unlock_vma() drops mmap_lock, as > - * the VMA may be split, merged, or freed after that. > + * On NOMMU configurations, returns with the mmap_lock held. If the MMU > + * is enabled, the per-VMA lock will be held instead. The lock > + * should be released with stack_map_unlock_vma() which will release the > + * appropriate lock. Once the lock is released, the VMA may be freed. Thanks! > * > * Returns NULL on failure, in which case no lock is held. > */ > @@ -288,7 +285,6 @@ stack_map_lock_vma(struct stack_map_vma_lock *lock, unsigned long ip) > struct mm_struct *mm = lock->mm; > struct vm_area_struct *vma; > > - /* noop under !CONFIG_PER_VMA_LOCK */ > vma = lock_vma_under_rcu(mm, ip); > if (vma) { > lock->vma = vma; > @@ -308,21 +304,20 @@ stack_map_lock_vma(struct stack_map_vma_lock *lock, unsigned long ip) > return NULL; > } > > -#ifdef CONFIG_PER_VMA_LOCK > +#ifdef CONFIG_MMU > if (!vma_start_read_locked(vma)) { > mmap_read_unlock(mm); > return NULL; > } > mmap_read_unlock(mm); > #endif > - > lock->vma = vma; > return vma; > } > > static void stack_map_unlock_vma(struct stack_map_vma_lock *lock) > { > -#ifdef CONFIG_PER_VMA_LOCK > +#ifdef CONFIG_MMU > vma_end_read(lock->vma); > #else > mmap_read_unlock(lock->mm); > diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c > index e791ae065c39..245f74ec491d 100644 > --- a/kernel/bpf/task_iter.c > +++ b/kernel/bpf/task_iter.c > @@ -835,7 +835,7 @@ __bpf_kfunc int bpf_iter_task_vma_new(struct bpf_iter_task_vma *it, > 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)) { > + if (!IS_ENABLED(CONFIG_MMU)) { > kit->data = NULL; > return -EOPNOTSUPP; > } > diff --git a/kernel/fork.c b/kernel/fork.c > index f0e2e131a9a5..ff91f5f66c80 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -1077,9 +1077,7 @@ static void mmap_init_lock(struct mm_struct *mm) > { > 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 --git a/mm/Kconfig b/mm/Kconfig > index 8a24c130d008..bf89d7d3be4b 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -1429,18 +1429,6 @@ config LRU_GEN_WALKS_MMU > 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 > depends on !STACK_GROWSUP > diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug > index 5737a504efbb..1dd150edfe71 100644 > --- a/mm/Kconfig.debug > +++ b/mm/Kconfig.debug > @@ -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 --git a/mm/debug.c b/mm/debug.c > index 9a0297b3988d..655e6bcc0e8d 100644 > --- a/mm/debug.c > +++ b/mm/debug.c > @@ -157,17 +157,13 @@ void dump_vma(const struct vm_area_struct *vma) > 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_start_pgoff(vma), > 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 --git a/mm/init-mm.c b/mm/init-mm.c > index 3e792aad7626..a1bb2c2d0284 100644 > --- a/mm/init-mm.c > +++ b/mm/init-mm.c > @@ -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 > #ifdef CONFIG_SCHED_MM_CID > .mm_cid.lock = __RAW_SPIN_LOCK_UNLOCKED(init_mm.mm_cid.lock), > #endif > diff --git a/mm/memory.c b/mm/memory.c > index 4134ac607ee0..21a4d95cb409 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -6818,7 +6818,6 @@ static vm_fault_t sanitize_fault_flags(struct vm_area_struct *vma, > !vma_is_cow_mapping(vma))) > 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. > @@ -6827,7 +6826,6 @@ static vm_fault_t sanitize_fault_flags(struct vm_area_struct *vma, > (FAULT_FLAG_VMA_LOCK | FAULT_FLAG_RETRY_NOWAIT)) == > (FAULT_FLAG_VMA_LOCK | FAULT_FLAG_RETRY_NOWAIT))) > return VM_FAULT_SIGSEGV; > -#endif > > return 0; > } > diff --git a/mm/mmap_lock.c b/mm/mmap_lock.c > index 898c2ef1e958..272f9ac762b9 100644 > --- a/mm/mmap_lock.c > +++ b/mm/mmap_lock.c > @@ -43,9 +43,6 @@ void __mmap_lock_do_trace_released(struct mm_struct *mm, bool write) > 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. */ > @@ -299,6 +296,8 @@ struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm, > MA_STATE(mas, &mm->mm_mt, address, address); > struct vm_area_struct *vma; > > + if (!IS_ENABLED(CONFIG_MMU)) > + return NULL; Thanks, I do think that's the least-worst solution :) > retry: > rcu_read_lock(); > vma = mas_walk(&mas); > @@ -431,7 +430,6 @@ struct vm_area_struct *lock_next_vma(struct mm_struct *mm, > > return vma; > } > -#endif /* CONFIG_PER_VMA_LOCK */ > > #ifdef CONFIG_LOCK_MM_AND_FIND_VMA > #include > @@ -548,23 +546,3 @@ struct vm_area_struct *lock_mm_and_find_vma(struct mm_struct *mm, > 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; > -} > - > -#endif /* CONFIG_MMU */ > diff --git a/mm/pagewalk.c b/mm/pagewalk.c > index cc07fcf50e87..7411702a37f5 100644 > --- a/mm/pagewalk.c > +++ b/mm/pagewalk.c > @@ -444,7 +444,6 @@ static inline void process_mm_walk_lock(struct mm_struct *mm, > 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); > @@ -459,7 +458,6 @@ static inline void process_vma_walk_lock(struct vm_area_struct *vma, > /* PGWALK_RDLOCK is handled by process_mm_walk_lock */ > break; > } > -#endif > } > > /* > diff --git a/mm/rmap.c b/mm/rmap.c > index 14f2f9b07572..7515220dfea4 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -260,11 +260,9 @@ static void check_anon_vma_clone(struct vm_area_struct *dst, > /* 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 --git a/mm/userfaultfd.c b/mm/userfaultfd.c > index 23fb68fce000..0b279b82eaa6 100644 > --- a/mm/userfaultfd.c > +++ b/mm/userfaultfd.c > @@ -122,7 +122,6 @@ struct vm_area_struct *find_vma_and_prepare_anon(struct mm_struct *mm, > return vma; > } > > -#ifdef CONFIG_PER_VMA_LOCK > /* > * uffd_lock_vma() - Lookup and lock vma corresponding to @address. > * @mm: mm to search vma in. > @@ -182,34 +181,6 @@ static void uffd_mfill_unlock(struct vm_area_struct *vma) > 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) > @@ -1850,7 +1821,6 @@ int find_vmas_mm_locked(struct mm_struct *mm, > return 0; > } > > -#ifdef CONFIG_PER_VMA_LOCK > static int uffd_move_lock(struct mm_struct *mm, > unsigned long dst_start, > unsigned long src_start, > @@ -1925,31 +1895,6 @@ static void uffd_move_unlock(struct vm_area_struct *dst_vma, > 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 --git a/rust/kernel/mm.rs b/rust/kernel/mm.rs > index 4764d7b68f2a..f4fa54616085 100644 > --- a/rust/kernel/mm.rs > +++ b/rust/kernel/mm.rs > @@ -170,30 +170,20 @@ pub unsafe fn from_raw<'a>(ptr: *const bindings::mm_struct) -> &'a MmWithUser { > /// > /// This is an optimistic trylock operation, so it may fail if there is contention. In that > /// case, you should fall back to taking the mmap read lock. > - /// > - /// When per-vma locks are disabled, this always returns `None`. > #[inline] > pub fn lock_vma_under_rcu(&self, vma_addr: usize) -> Option> { > - #[cfg(CONFIG_PER_VMA_LOCK)] > - { > - // SAFETY: Calling `bindings::lock_vma_under_rcu` is always okay given an mm where > - // `mm_users` is non-zero. > - let vma = unsafe { bindings::lock_vma_under_rcu(self.as_raw(), vma_addr) }; > - if !vma.is_null() { > - return Some(VmaReadGuard { > - // SAFETY: If `lock_vma_under_rcu` returns a non-null ptr, then it points at a > - // valid vma. The vma is stable for as long as the vma read lock is held. > - vma: unsafe { VmaRef::from_raw(vma) }, > - _nts: NotThreadSafe, > - }); > - } > + // SAFETY: Calling `bindings::lock_vma_under_rcu` is always okay given an mm where > + // `mm_users` is non-zero. > + let vma = unsafe { bindings::lock_vma_under_rcu(self.as_raw(), vma_addr) }; > + if vma.is_null() { > + return None; > } > - > - // Silence warnings about unused variables. > - #[cfg(not(CONFIG_PER_VMA_LOCK))] > - let _ = vma_addr; > - > - None > + Some(VmaReadGuard { > + // SAFETY: If `lock_vma_under_rcu` returns a non-null ptr, then it points at a > + // valid vma. The vma is stable for as long as the vma read lock is held. > + vma: unsafe { VmaRef::from_raw(vma) }, > + _nts: NotThreadSafe, > + }) > } > > /// Lock the mmap read lock. > diff --git a/tools/testing/vma/include/dup.h b/tools/testing/vma/include/dup.h > index 41203b1c2323..a0d1d563da24 100644 > --- a/tools/testing/vma/include/dup.h > +++ b/tools/testing/vma/include/dup.h > @@ -582,7 +582,6 @@ 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) > @@ -598,7 +597,7 @@ struct vm_area_struct { > * slowpath. > */ > unsigned int vm_lock_seq; > -#endif > + > unsigned int __vm_anon_pgoff_lo; > > /* > @@ -632,10 +631,8 @@ 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 > #ifdef CONFIG_64BIT > unsigned int __vm_anon_pgoff_hi; > #endif > diff --git a/tools/testing/vma/vma_internal.h b/tools/testing/vma/vma_internal.h > index 8a48b231aa7a..54d5c3360aa2 100644 > --- a/tools/testing/vma/vma_internal.h > +++ b/tools/testing/vma/vma_internal.h > @@ -15,7 +15,6 @@ > #include > > #define CONFIG_MMU 1 > -#define CONFIG_PER_VMA_LOCK 1 > > #ifdef __CONCAT > #undef __CONCAT > -- > 2.55.0.691.gc56d675ccc-goog > -- Cheers, Lorenzo