[PATCH] xen: simplify balloon_first_page() with list_first_entry_or_null()

[PATCH] xen: simplify balloon_first_page() with list_first_entry_or_null()

[Jeff Liu]

From: Jie Liu <jeff.liu@oracle.com>

Simplify the code logic of balloon_first_page() by replacing
the combination of list_empty() and list_first_entry() with
list_first_entry_or_null().  As a net win, we can change this
routine to inline as now it's one line.

Signed-off-by: Jie Liu <jeff.liu@oracle.com>

---
 drivers/xen/balloon.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index b232908..0e4ca20 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -157,11 +157,10 @@ static struct page *balloon_retrieve(bool prefer_highmem)
 	return page;
 }
 
-static struct page *balloon_first_page(void)
+static inline struct page *balloon_first_page(void)
 {
-	if (list_empty(&ballooned_pages))
-		return NULL;
-	return list_entry(ballooned_pages.next, struct page, lru);
+	return list_first_entry_or_null(&ballooned_pages,
+					struct page, lru);
 }
 
 static struct page *balloon_next_page(struct page *page)
-- 
1.7.9.5

Re: [PATCH] xen: simplify balloon_first_page() with list_first_entry_or_null()

[David Vrabel]

On 13/11/13 11:44, Jeff Liu wrote:
> From: Jie Liu <jeff.liu@oracle.com>
> 
> Simplify the code logic of balloon_first_page() by replacing
> the combination of list_empty() and list_first_entry() with
> list_first_entry_or_null().  As a net win, we can change this
> routine to inline as now it's one line.
> 
> Signed-off-by: Jie Liu <jeff.liu@oracle.com>
> 
> ---
>  drivers/xen/balloon.c |    7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> index b232908..0e4ca20 100644
> --- a/drivers/xen/balloon.c
> +++ b/drivers/xen/balloon.c
> @@ -157,11 +157,10 @@ static struct page *balloon_retrieve(bool prefer_highmem)
>  	return page;
>  }
>  
> -static struct page *balloon_first_page(void)
> +static inline struct page *balloon_first_page(void)
>  {
> -	if (list_empty(&ballooned_pages))
> -		return NULL;
> -	return list_entry(ballooned_pages.next, struct page, lru);
> +	return list_first_entry_or_null(&ballooned_pages,
> +					struct page, lru);
>  }

There's only one user of balloon_first_page(), can you remove
balloon_first_page() and just use list_first_entry_or_null()?

David

Re: [PATCH] xen: simplify balloon_first_page() with list_first_entry_or_null()

[Jeff Liu]

On 11/13, 2013 20:09 PM, David Vrabel wrote:
> On 13/11/13 11:44, Jeff Liu wrote:
>> From: Jie Liu <jeff.liu@oracle.com>
>>
>> Simplify the code logic of balloon_first_page() by replacing
>> the combination of list_empty() and list_first_entry() with
>> list_first_entry_or_null().  As a net win, we can change this
>> routine to inline as now it's one line.
>>
>> Signed-off-by: Jie Liu <jeff.liu@oracle.com>
>>
>> ---
>>  drivers/xen/balloon.c |    7 +++----
>>  1 file changed, 3 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
>> index b232908..0e4ca20 100644
>> --- a/drivers/xen/balloon.c
>> +++ b/drivers/xen/balloon.c
>> @@ -157,11 +157,10 @@ static struct page *balloon_retrieve(bool prefer_highmem)
>>  	return page;
>>  }
>>  
>> -static struct page *balloon_first_page(void)
>> +static inline struct page *balloon_first_page(void)
>>  {
>> -	if (list_empty(&ballooned_pages))
>> -		return NULL;
>> -	return list_entry(ballooned_pages.next, struct page, lru);
>> +	return list_first_entry_or_null(&ballooned_pages,
>> +					struct page, lru);
>>  }
> 
> There's only one user of balloon_first_page(), can you remove
> balloon_first_page() and just use list_first_entry_or_null()?
Sure, will post the revised version a little while.

Thanks,
-Jeff