[v2] mm/mmap.c: refine find_vma_prev with rb_last
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Message ID 20190809001928.4950-1-richardw.yang@linux.intel.com
State New
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Series
  • [v2] mm/mmap.c: refine find_vma_prev with rb_last
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Commit Message

Wei Yang Aug. 9, 2019, 12:19 a.m. UTC
When addr is out of the range of the whole rb_tree, pprev will points to
the right-most node. rb_tree facility already provides a helper
function, rb_last, to do this task. We can leverage this instead of
re-implement it.

This patch refines find_vma_prev with rb_last to make it a little nicer
to read.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>

---
v2: leverage rb_last
---
 mm/mmap.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

Comments

Vlastimil Babka Aug. 9, 2019, 8:03 a.m. UTC | #1
On 8/9/19 2:19 AM, Wei Yang wrote:
> When addr is out of the range of the whole rb_tree, pprev will points to
> the right-most node. rb_tree facility already provides a helper
> function, rb_last, to do this task. We can leverage this instead of
> re-implement it.
> 
> This patch refines find_vma_prev with rb_last to make it a little nicer
> to read.
> 
> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

Nit below:

> ---
> v2: leverage rb_last
> ---
>  mm/mmap.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 7e8c3e8ae75f..f7ed0afb994c 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2270,12 +2270,9 @@ find_vma_prev(struct mm_struct *mm, unsigned long addr,
>  	if (vma) {
>  		*pprev = vma->vm_prev;
>  	} else {
> -		struct rb_node *rb_node = mm->mm_rb.rb_node;
> -		*pprev = NULL;
> -		while (rb_node) {
> -			*pprev = rb_entry(rb_node, struct vm_area_struct, vm_rb);
> -			rb_node = rb_node->rb_right;
> -		}
> +		struct rb_node *rb_node = rb_last(&mm->mm_rb);
> +		*pprev = !rb_node ? NULL :
> +			 rb_entry(rb_node, struct vm_area_struct, vm_rb);

It's perhaps more common to write it like:
*pprev = rb_node ? rb_entry(rb_node, struct vm_area_struct, vm_rb) : NULL;

>  	}
>  	return vma;
>  }
>
Wei Yang Aug. 9, 2019, 8:31 a.m. UTC | #2
On Fri, Aug 09, 2019 at 10:03:20AM +0200, Vlastimil Babka wrote:
>On 8/9/19 2:19 AM, Wei Yang wrote:
>> When addr is out of the range of the whole rb_tree, pprev will points to
>> the right-most node. rb_tree facility already provides a helper
>> function, rb_last, to do this task. We can leverage this instead of
>> re-implement it.
>> 
>> This patch refines find_vma_prev with rb_last to make it a little nicer
>> to read.
>> 
>> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
>
>Acked-by: Vlastimil Babka <vbabka@suse.cz>
>
>Nit below:
>
>> ---
>> v2: leverage rb_last
>> ---
>>  mm/mmap.c | 9 +++------
>>  1 file changed, 3 insertions(+), 6 deletions(-)
>> 
>> diff --git a/mm/mmap.c b/mm/mmap.c
>> index 7e8c3e8ae75f..f7ed0afb994c 100644
>> --- a/mm/mmap.c
>> +++ b/mm/mmap.c
>> @@ -2270,12 +2270,9 @@ find_vma_prev(struct mm_struct *mm, unsigned long addr,
>>  	if (vma) {
>>  		*pprev = vma->vm_prev;
>>  	} else {
>> -		struct rb_node *rb_node = mm->mm_rb.rb_node;
>> -		*pprev = NULL;
>> -		while (rb_node) {
>> -			*pprev = rb_entry(rb_node, struct vm_area_struct, vm_rb);
>> -			rb_node = rb_node->rb_right;
>> -		}
>> +		struct rb_node *rb_node = rb_last(&mm->mm_rb);
>> +		*pprev = !rb_node ? NULL :
>> +			 rb_entry(rb_node, struct vm_area_struct, vm_rb);
>
>It's perhaps more common to write it like:
>*pprev = rb_node ? rb_entry(rb_node, struct vm_area_struct, vm_rb) : NULL;
>

Do you prefer me to send v3 with this updated?

>>  	}
>>  	return vma;
>>  }
>>

Patch
diff mbox series

diff --git a/mm/mmap.c b/mm/mmap.c
index 7e8c3e8ae75f..f7ed0afb994c 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2270,12 +2270,9 @@  find_vma_prev(struct mm_struct *mm, unsigned long addr,
 	if (vma) {
 		*pprev = vma->vm_prev;
 	} else {
-		struct rb_node *rb_node = mm->mm_rb.rb_node;
-		*pprev = NULL;
-		while (rb_node) {
-			*pprev = rb_entry(rb_node, struct vm_area_struct, vm_rb);
-			rb_node = rb_node->rb_right;
-		}
+		struct rb_node *rb_node = rb_last(&mm->mm_rb);
+		*pprev = !rb_node ? NULL :
+			 rb_entry(rb_node, struct vm_area_struct, vm_rb);
 	}
 	return vma;
 }