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[PATCH v4 2/7] mm: introduce vma->vm_flags wrapper functions

Suren Baghdasaryan posted 7 patches 1 year, 9 months ago
[PATCH v4 2/7] mm: introduce vma->vm_flags wrapper functions
Posted by Suren Baghdasaryan 1 year, 9 months ago 
vm_flags are among VMA attributes which affect decisions like VMA merging
and splitting. Therefore all vm_flags modifications are performed after
taking exclusive mmap_lock to prevent vm_flags updates racing with such
operations. Introduce modifier functions for vm_flags to be used whenever
flags are updated. This way we can better check and control correct
locking behavior during these updates.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
---
 include/linux/mm.h       | 40 ++++++++++++++++++++++++++++++++++++++++
 include/linux/mm_types.h | 10 +++++++++-
 2 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 8d636e895ee9..abb31103d060 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -627,6 +627,46 @@ static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm)
 	INIT_LIST_HEAD(&vma->anon_vma_chain);
 }
 
+/* Use when VMA is not part of the VMA tree and needs no locking */
+static inline void vm_flags_init(struct vm_area_struct *vma,
+				 vm_flags_t flags)
+{
+	ACCESS_PRIVATE(vma, __vm_flags) = flags;
+}
+
+/* Use when VMA is part of the VMA tree and modifications need coordination */
+static inline void vm_flags_reset(struct vm_area_struct *vma,
+				  vm_flags_t flags)
+{
+	mmap_assert_write_locked(vma->vm_mm);
+	vm_flags_init(vma, flags);
+}
+
+static inline void vm_flags_set(struct vm_area_struct *vma,
+				vm_flags_t flags)
+{
+	mmap_assert_write_locked(vma->vm_mm);
+	ACCESS_PRIVATE(vma, __vm_flags) |= flags;
+}
+
+static inline void vm_flags_clear(struct vm_area_struct *vma,
+				  vm_flags_t flags)
+{
+	mmap_assert_write_locked(vma->vm_mm);
+	ACCESS_PRIVATE(vma, __vm_flags) &= ~flags;
+}
+
+/*
+ * Use only when the order of set/clear operations is unimportant, otherwise
+ * use vm_flags_{set|clear} explicitly.
+ */
+static inline void vm_flags_mod(struct vm_area_struct *vma,
+				vm_flags_t set, vm_flags_t clear)
+{
+	mmap_assert_write_locked(vma->vm_mm);
+	vm_flags_init(vma, (vma->vm_flags | set) & ~clear);
+}
+
 static inline void vma_set_anonymous(struct vm_area_struct *vma)
 {
 	vma->vm_ops = NULL;
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 2d6d790d9bed..da983aedb741 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -491,7 +491,15 @@ struct vm_area_struct {
 	 * See vmf_insert_mixed_prot() for discussion.
 	 */
 	pgprot_t vm_page_prot;
-	unsigned long vm_flags;		/* Flags, see mm.h. */
+
+	/*
+	 * Flags, see mm.h.
+	 * To modify use vm_flags_{init|reset|set|clear|mod} functions.
+	 */
+	union {
+		const vm_flags_t vm_flags;
+		vm_flags_t __private __vm_flags;
+	};
 
 	/*
 	 * For areas with an address space and backing store,
-- 
2.39.1
Re: [PATCH v4 2/7] mm: introduce vma->vm_flags wrapper functions
Posted by Hyeonggon Yoo 1 year, 9 months ago 
On Thu, Jan 26, 2023 at 11:37:47AM -0800, Suren Baghdasaryan wrote:
> vm_flags are among VMA attributes which affect decisions like VMA merging
> and splitting. Therefore all vm_flags modifications are performed after
> taking exclusive mmap_lock to prevent vm_flags updates racing with such
> operations. Introduce modifier functions for vm_flags to be used whenever
> flags are updated. This way we can better check and control correct
> locking behavior during these updates.
> 
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
> Acked-by: Michal Hocko <mhocko@suse.com>
> Acked-by: Mel Gorman <mgorman@techsingularity.net>
> ---
>  include/linux/mm.h       | 40 ++++++++++++++++++++++++++++++++++++++++
>  include/linux/mm_types.h | 10 +++++++++-
>  2 files changed, 49 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 8d636e895ee9..abb31103d060 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -627,6 +627,46 @@ static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm)
>  	INIT_LIST_HEAD(&vma->anon_vma_chain);
>  }
>  
> +/* Use when VMA is not part of the VMA tree and needs no locking */
> +static inline void vm_flags_init(struct vm_area_struct *vma,
> +				 vm_flags_t flags)
> +{
> +	ACCESS_PRIVATE(vma, __vm_flags) = flags;
> +}
> +
> +/* Use when VMA is part of the VMA tree and modifications need coordination */
> +static inline void vm_flags_reset(struct vm_area_struct *vma,
> +				  vm_flags_t flags)
> +{
> +	mmap_assert_write_locked(vma->vm_mm);
> +	vm_flags_init(vma, flags);
> +}
> +
> +static inline void vm_flags_set(struct vm_area_struct *vma,
> +				vm_flags_t flags)
> +{
> +	mmap_assert_write_locked(vma->vm_mm);
> +	ACCESS_PRIVATE(vma, __vm_flags) |= flags;
> +}
> +
> +static inline void vm_flags_clear(struct vm_area_struct *vma,
> +				  vm_flags_t flags)
> +{
> +	mmap_assert_write_locked(vma->vm_mm);
> +	ACCESS_PRIVATE(vma, __vm_flags) &= ~flags;
> +}
> +
> +/*
> + * Use only when the order of set/clear operations is unimportant, otherwise
> + * use vm_flags_{set|clear} explicitly.
> + */
> +static inline void vm_flags_mod(struct vm_area_struct *vma,
> +				vm_flags_t set, vm_flags_t clear)
> +{
> +	mmap_assert_write_locked(vma->vm_mm);
> +	vm_flags_init(vma, (vma->vm_flags | set) & ~clear);
> +}
> +
>  static inline void vma_set_anonymous(struct vm_area_struct *vma)
>  {
>  	vma->vm_ops = NULL;
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 2d6d790d9bed..da983aedb741 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -491,7 +491,15 @@ struct vm_area_struct {
>  	 * See vmf_insert_mixed_prot() for discussion.
>  	 */
>  	pgprot_t vm_page_prot;
> -	unsigned long vm_flags;		/* Flags, see mm.h. */
> +
> +	/*
> +	 * Flags, see mm.h.
> +	 * To modify use vm_flags_{init|reset|set|clear|mod} functions.
> +	 */
> +	union {
> +		const vm_flags_t vm_flags;
> +		vm_flags_t __private __vm_flags;
> +	};
>  
>  	/*
>  	 * For areas with an address space and backing store,

Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>

> -- 
> 2.39.1
> 
>
Re: [PATCH v4 2/7] mm: introduce vma->vm_flags wrapper functions
Posted by Mike Rapoport 1 year, 9 months ago 
On Thu, Jan 26, 2023 at 11:37:47AM -0800, Suren Baghdasaryan wrote:
> vm_flags are among VMA attributes which affect decisions like VMA merging
> and splitting. Therefore all vm_flags modifications are performed after
> taking exclusive mmap_lock to prevent vm_flags updates racing with such
> operations. Introduce modifier functions for vm_flags to be used whenever
> flags are updated. This way we can better check and control correct
> locking behavior during these updates.
> 
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
> Acked-by: Michal Hocko <mhocko@suse.com>
> Acked-by: Mel Gorman <mgorman@techsingularity.net>

Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>

> ---
>  include/linux/mm.h       | 40 ++++++++++++++++++++++++++++++++++++++++
>  include/linux/mm_types.h | 10 +++++++++-
>  2 files changed, 49 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 8d636e895ee9..abb31103d060 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -627,6 +627,46 @@ static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm)
>  	INIT_LIST_HEAD(&vma->anon_vma_chain);
>  }
>  
> +/* Use when VMA is not part of the VMA tree and needs no locking */
> +static inline void vm_flags_init(struct vm_area_struct *vma,
> +				 vm_flags_t flags)
> +{
> +	ACCESS_PRIVATE(vma, __vm_flags) = flags;
> +}
> +
> +/* Use when VMA is part of the VMA tree and modifications need coordination */
> +static inline void vm_flags_reset(struct vm_area_struct *vma,
> +				  vm_flags_t flags)
> +{
> +	mmap_assert_write_locked(vma->vm_mm);
> +	vm_flags_init(vma, flags);
> +}
> +
> +static inline void vm_flags_set(struct vm_area_struct *vma,
> +				vm_flags_t flags)
> +{
> +	mmap_assert_write_locked(vma->vm_mm);
> +	ACCESS_PRIVATE(vma, __vm_flags) |= flags;
> +}
> +
> +static inline void vm_flags_clear(struct vm_area_struct *vma,
> +				  vm_flags_t flags)
> +{
> +	mmap_assert_write_locked(vma->vm_mm);
> +	ACCESS_PRIVATE(vma, __vm_flags) &= ~flags;
> +}
> +
> +/*
> + * Use only when the order of set/clear operations is unimportant, otherwise
> + * use vm_flags_{set|clear} explicitly.
> + */
> +static inline void vm_flags_mod(struct vm_area_struct *vma,
> +				vm_flags_t set, vm_flags_t clear)
> +{
> +	mmap_assert_write_locked(vma->vm_mm);
> +	vm_flags_init(vma, (vma->vm_flags | set) & ~clear);
> +}
> +
>  static inline void vma_set_anonymous(struct vm_area_struct *vma)
>  {
>  	vma->vm_ops = NULL;
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 2d6d790d9bed..da983aedb741 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -491,7 +491,15 @@ struct vm_area_struct {
>  	 * See vmf_insert_mixed_prot() for discussion.
>  	 */
>  	pgprot_t vm_page_prot;
> -	unsigned long vm_flags;		/* Flags, see mm.h. */
> +
> +	/*
> +	 * Flags, see mm.h.
> +	 * To modify use vm_flags_{init|reset|set|clear|mod} functions.
> +	 */
> +	union {
> +		const vm_flags_t vm_flags;
> +		vm_flags_t __private __vm_flags;
> +	};
>  
>  	/*
>  	 * For areas with an address space and backing store,
> -- 
> 2.39.1
> 

-- 
Sincerely yours,
Mike.

Patchew 2.1-devel-b67e4c2

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