[PATCH v2 0/2] mm/mmap: simplify vma_merge()

[PATCH v2 0/2] mm/mmap: simplify vma_merge()

[Yajun Deng]

The vma_merge() has too many parameters, we can pass vma to vma_merge(),
so that it can save two parameters.
Since the src vma was passed, find_vma_intersection() can be removed.

v2: split it into two patches.
v1: https://lore.kernel.org/all/20240118082312.2801992-1-yajun.deng@linux.dev/

Yajun Deng (2):
  mm/mmap: pass vma to vma_merge()
  mm/mmap: remove find_vma_intersection() in vma_merge()

 mm/mmap.c | 42 ++++++++++++++++++++++--------------------
 1 file changed, 22 insertions(+), 20 deletions(-)

-- 
2.25.1

[PATCH v2 1/2] mm/mmap: pass vma to vma_merge()

[Yajun Deng]

These vma_merge() callers will pass mm, anon_vma and file, they all from
the same vma. There is no need to pass three parameters at the same time.

Pass vma instead of mm, anon_vma and file to vma_merge(), so that it can
save two parameters.

Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
---
 mm/mmap.c | 27 +++++++++++++--------------
 1 file changed, 13 insertions(+), 14 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 49d25172eac8..f19bc53bc08e 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -860,13 +860,15 @@ can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
  *      area is returned, or the function will return NULL
  */
 static struct vm_area_struct
-*vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
-	   struct vm_area_struct *prev, unsigned long addr, unsigned long end,
-	   unsigned long vm_flags, struct anon_vma *anon_vma, struct file *file,
-	   pgoff_t pgoff, struct mempolicy *policy,
+*vma_merge(struct vma_iterator *vmi, struct vm_area_struct *prev,
+	   struct vm_area_struct *src, unsigned long addr, unsigned long end,
+	   unsigned long vm_flags, pgoff_t pgoff, struct mempolicy *policy,
 	   struct vm_userfaultfd_ctx vm_userfaultfd_ctx,
 	   struct anon_vma_name *anon_name)
 {
+	struct mm_struct *mm = src->vm_mm;
+	struct anon_vma *anon_vma = src->anon_vma;
+	struct file *file = src->vm_file;
 	struct vm_area_struct *curr, *next, *res;
 	struct vm_area_struct *vma, *adjust, *remove, *remove2;
 	struct vm_area_struct *anon_dup = NULL;
@@ -2424,9 +2426,8 @@ struct vm_area_struct *vma_modify(struct vma_iterator *vmi,
 	pgoff_t pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
 	struct vm_area_struct *merged;
 
-	merged = vma_merge(vmi, vma->vm_mm, prev, start, end, vm_flags,
-			   vma->anon_vma, vma->vm_file, pgoff, policy,
-			   uffd_ctx, anon_name);
+	merged = vma_merge(vmi, prev, vma, start, end, vm_flags,
+			   pgoff, policy, uffd_ctx, anon_name);
 	if (merged)
 		return merged;
 
@@ -2456,9 +2457,8 @@ static struct vm_area_struct
 		   struct vm_area_struct *vma, unsigned long start,
 		   unsigned long end, pgoff_t pgoff)
 {
-	return vma_merge(vmi, vma->vm_mm, prev, start, end, vma->vm_flags,
-			 vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
-			 vma->vm_userfaultfd_ctx, anon_vma_name(vma));
+	return vma_merge(vmi, prev, vma, start, end, vma->vm_flags, pgoff,
+			 vma_policy(vma), vma->vm_userfaultfd_ctx, anon_vma_name(vma));
 }
 
 /*
@@ -2472,10 +2472,9 @@ struct vm_area_struct *vma_merge_extend(struct vma_iterator *vmi,
 	pgoff_t pgoff = vma->vm_pgoff + vma_pages(vma);
 
 	/* vma is specified as prev, so case 1 or 2 will apply. */
-	return vma_merge(vmi, vma->vm_mm, vma, vma->vm_end, vma->vm_end + delta,
-			 vma->vm_flags, vma->anon_vma, vma->vm_file, pgoff,
-			 vma_policy(vma), vma->vm_userfaultfd_ctx,
-			 anon_vma_name(vma));
+	return vma_merge(vmi, vma, vma, vma->vm_end, vma->vm_end + delta,
+			 vma->vm_flags, pgoff, vma_policy(vma),
+			 vma->vm_userfaultfd_ctx, anon_vma_name(vma));
 }
 
 /*
-- 
2.25.1

Re: [PATCH v2 1/2] mm/mmap: pass vma to vma_merge()

[Liam R. Howlett]

* Yajun Deng <yajun.deng@linux.dev> [240124 22:49]:
> These vma_merge() callers will pass mm, anon_vma and file, they all from
> the same vma. There is no need to pass three parameters at the same time.
> 
> Pass vma instead of mm, anon_vma and file to vma_merge(), so that it can
> save two parameters.
> 
> Signed-off-by: Yajun Deng <yajun.deng@linux.dev>

Thanks for splitting these up.

Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>

> ---
>  mm/mmap.c | 27 +++++++++++++--------------
>  1 file changed, 13 insertions(+), 14 deletions(-)
> 
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 49d25172eac8..f19bc53bc08e 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -860,13 +860,15 @@ can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
>   *      area is returned, or the function will return NULL
>   */
>  static struct vm_area_struct
> -*vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
> -	   struct vm_area_struct *prev, unsigned long addr, unsigned long end,
> -	   unsigned long vm_flags, struct anon_vma *anon_vma, struct file *file,
> -	   pgoff_t pgoff, struct mempolicy *policy,
> +*vma_merge(struct vma_iterator *vmi, struct vm_area_struct *prev,
> +	   struct vm_area_struct *src, unsigned long addr, unsigned long end,
> +	   unsigned long vm_flags, pgoff_t pgoff, struct mempolicy *policy,
>  	   struct vm_userfaultfd_ctx vm_userfaultfd_ctx,
>  	   struct anon_vma_name *anon_name)
>  {
> +	struct mm_struct *mm = src->vm_mm;
> +	struct anon_vma *anon_vma = src->anon_vma;
> +	struct file *file = src->vm_file;
>  	struct vm_area_struct *curr, *next, *res;
>  	struct vm_area_struct *vma, *adjust, *remove, *remove2;
>  	struct vm_area_struct *anon_dup = NULL;
> @@ -2424,9 +2426,8 @@ struct vm_area_struct *vma_modify(struct vma_iterator *vmi,
>  	pgoff_t pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
>  	struct vm_area_struct *merged;
>  
> -	merged = vma_merge(vmi, vma->vm_mm, prev, start, end, vm_flags,
> -			   vma->anon_vma, vma->vm_file, pgoff, policy,
> -			   uffd_ctx, anon_name);
> +	merged = vma_merge(vmi, prev, vma, start, end, vm_flags,
> +			   pgoff, policy, uffd_ctx, anon_name);
>  	if (merged)
>  		return merged;
>  
> @@ -2456,9 +2457,8 @@ static struct vm_area_struct
>  		   struct vm_area_struct *vma, unsigned long start,
>  		   unsigned long end, pgoff_t pgoff)
>  {
> -	return vma_merge(vmi, vma->vm_mm, prev, start, end, vma->vm_flags,
> -			 vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
> -			 vma->vm_userfaultfd_ctx, anon_vma_name(vma));
> +	return vma_merge(vmi, prev, vma, start, end, vma->vm_flags, pgoff,
> +			 vma_policy(vma), vma->vm_userfaultfd_ctx, anon_vma_name(vma));
>  }
>  
>  /*
> @@ -2472,10 +2472,9 @@ struct vm_area_struct *vma_merge_extend(struct vma_iterator *vmi,
>  	pgoff_t pgoff = vma->vm_pgoff + vma_pages(vma);
>  
>  	/* vma is specified as prev, so case 1 or 2 will apply. */
> -	return vma_merge(vmi, vma->vm_mm, vma, vma->vm_end, vma->vm_end + delta,
> -			 vma->vm_flags, vma->anon_vma, vma->vm_file, pgoff,
> -			 vma_policy(vma), vma->vm_userfaultfd_ctx,
> -			 anon_vma_name(vma));
> +	return vma_merge(vmi, vma, vma, vma->vm_end, vma->vm_end + delta,
> +			 vma->vm_flags, pgoff, vma_policy(vma),
> +			 vma->vm_userfaultfd_ctx, anon_vma_name(vma));
>  }
>  
>  /*
> -- 
> 2.25.1
> 

[PATCH v2 2/2] mm/mmap: remove find_vma_intersection() in vma_merge()

[Yajun Deng]

We need to find the current vma by find_vma_intersection() in
vma_merge(). Since the src vma was passed, we can add a check to figure
out if the current vma is NULL or the src vma directly.

Remove find_vma_intersection() in vma_merge(). And initialize the next to
NULL when defining it.

Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
---
 mm/mmap.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index f19bc53bc08e..ea02fdc91aa2 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -869,7 +869,7 @@ static struct vm_area_struct
 	struct mm_struct *mm = src->vm_mm;
 	struct anon_vma *anon_vma = src->anon_vma;
 	struct file *file = src->vm_file;
-	struct vm_area_struct *curr, *next, *res;
+	struct vm_area_struct *curr = src, *next = NULL, *res;
 	struct vm_area_struct *vma, *adjust, *remove, *remove2;
 	struct vm_area_struct *anon_dup = NULL;
 	struct vma_prepare vp;
@@ -890,14 +890,18 @@ static struct vm_area_struct
 	if (vm_flags & VM_SPECIAL)
 		return NULL;
 
-	/* Does the input range span an existing VMA? (cases 5 - 8) */
-	curr = find_vma_intersection(mm, prev ? prev->vm_end : 0, end);
+	/*
+	 * If the current vma and the prev vma are the same vma, it
+	 * means the current vma is NULL.
+	 * Does the input range span an existing VMA? (cases 5 - 8)
+	 */
+	if (prev == curr || addr != curr->vm_start || end > curr->vm_end)
+		curr = NULL;
 
 	if (!curr ||			/* cases 1 - 4 */
 	    end == curr->vm_end)	/* cases 6 - 8, adjacent VMA */
 		next = vma_lookup(mm, end);
-	else
-		next = NULL;		/* case 5 */
+					/* case 5 set to NULL above */
 
 	if (prev) {
 		vma_start = prev->vm_start;
@@ -921,7 +925,6 @@ static struct vm_area_struct
 
 	/* Verify some invariant that must be enforced by the caller. */
 	VM_WARN_ON(prev && addr <= prev->vm_start);
-	VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end));
 	VM_WARN_ON(addr >= end);
 
 	if (!merge_prev && !merge_next)
-- 
2.25.1

Re: [PATCH v2 2/2] mm/mmap: remove find_vma_intersection() in vma_merge()

[Liam R. Howlett]

* Yajun Deng <yajun.deng@linux.dev> [240124 22:50]:
> We need to find the current vma by find_vma_intersection() in
> vma_merge(). Since the src vma was passed, we can add a check to figure
> out if the current vma is NULL or the src vma directly.
> 
> Remove find_vma_intersection() in vma_merge(). And initialize the next to
> NULL when defining it.
> 
> Signed-off-by: Yajun Deng <yajun.deng@linux.dev>

Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>

> ---
>  mm/mmap.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/mmap.c b/mm/mmap.c
> index f19bc53bc08e..ea02fdc91aa2 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -869,7 +869,7 @@ static struct vm_area_struct
>  	struct mm_struct *mm = src->vm_mm;
>  	struct anon_vma *anon_vma = src->anon_vma;
>  	struct file *file = src->vm_file;
> -	struct vm_area_struct *curr, *next, *res;
> +	struct vm_area_struct *curr = src, *next = NULL, *res;
>  	struct vm_area_struct *vma, *adjust, *remove, *remove2;
>  	struct vm_area_struct *anon_dup = NULL;
>  	struct vma_prepare vp;
> @@ -890,14 +890,18 @@ static struct vm_area_struct
>  	if (vm_flags & VM_SPECIAL)
>  		return NULL;
>  
> -	/* Does the input range span an existing VMA? (cases 5 - 8) */
> -	curr = find_vma_intersection(mm, prev ? prev->vm_end : 0, end);
> +	/*
> +	 * If the current vma and the prev vma are the same vma, it
> +	 * means the current vma is NULL.
> +	 * Does the input range span an existing VMA? (cases 5 - 8)
> +	 */
> +	if (prev == curr || addr != curr->vm_start || end > curr->vm_end)
> +		curr = NULL;
>  
>  	if (!curr ||			/* cases 1 - 4 */
>  	    end == curr->vm_end)	/* cases 6 - 8, adjacent VMA */
>  		next = vma_lookup(mm, end);
> -	else
> -		next = NULL;		/* case 5 */
> +					/* case 5 set to NULL above */
>  
>  	if (prev) {
>  		vma_start = prev->vm_start;
> @@ -921,7 +925,6 @@ static struct vm_area_struct
>  
>  	/* Verify some invariant that must be enforced by the caller. */
>  	VM_WARN_ON(prev && addr <= prev->vm_start);
> -	VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end));
>  	VM_WARN_ON(addr >= end);
>  
>  	if (!merge_prev && !merge_next)
> -- 
> 2.25.1
>