[PATCH] mm/hugetlb: remove redundant reservation check condition in alloc_huge_page()

[PATCH] mm/hugetlb: remove redundant reservation check condition in alloc_huge_page()

[Miaohe Lin]

If there is no reservation corresponding to a vma, map_chg is always != 0,
i.e. we can not meet the condition where a vma does not have reservation
while map_chg = 0.

Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
 mm/hugetlb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 4f2c92ddbca4..36c3646fa55f 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2311,7 +2311,7 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
 
 	/* If this allocation is not consuming a reservation, charge it now.
 	 */
-	deferred_reserve = map_chg || avoid_reserve || !vma_resv_map(vma);
+	deferred_reserve = map_chg || avoid_reserve;
 	if (deferred_reserve) {
 		ret = hugetlb_cgroup_charge_cgroup_rsvd(
 			idx, pages_per_huge_page(h), &h_cg);
-- 
2.19.1

Re: [PATCH] mm/hugetlb: remove redundant reservation check condition in alloc_huge_page()

[Mike Kravetz]

On 2/9/21 11:54 PM, Miaohe Lin wrote:
> If there is no reservation corresponding to a vma, map_chg is always != 0,
> i.e. we can not meet the condition where a vma does not have reservation
> while map_chg = 0.

This commit message might be easier to understand?

vma_resv_map(vma) checks if a reserve map is associated with the vma.  The
routine vma_needs_reservation() will check vma_resv_map(vma) and return 1
if no reserv map is present.  map_chg is set to the return value of
vma_needs_reservation().  Therefore, !vma_resv_map(vma) is redundant in the
expression:
	map_chg || avoid_reserve || !vma_resv_map(vma);
Remove the redundant check.

-- 
Mike Kravetz

> 
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
>  mm/hugetlb.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 4f2c92ddbca4..36c3646fa55f 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2311,7 +2311,7 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
>  
>  	/* If this allocation is not consuming a reservation, charge it now.
>  	 */
> -	deferred_reserve = map_chg || avoid_reserve || !vma_resv_map(vma);
> +	deferred_reserve = map_chg || avoid_reserve;
>  	if (deferred_reserve) {
>  		ret = hugetlb_cgroup_charge_cgroup_rsvd(
>  			idx, pages_per_huge_page(h), &h_cg);
> 

Re: [PATCH] mm/hugetlb: remove redundant reservation check condition in alloc_huge_page()

[Miaohe Lin]

Hi:
On 2021/2/13 9:15, Mike Kravetz wrote:
> On 2/9/21 11:54 PM, Miaohe Lin wrote:
>> If there is no reservation corresponding to a vma, map_chg is always != 0,
>> i.e. we can not meet the condition where a vma does not have reservation
>> while map_chg = 0.
> 
> This commit message might be easier to understand?
> 
> vma_resv_map(vma) checks if a reserve map is associated with the vma.  The
> routine vma_needs_reservation() will check vma_resv_map(vma) and return 1
> if no reserv map is present.  map_chg is set to the return value of
> vma_needs_reservation().  Therefore, !vma_resv_map(vma) is redundant in the
> expression:
> 	map_chg || avoid_reserve || !vma_resv_map(vma);
> Remove the redundant check.
> 

Sorry for late respond! I will use this wonderful commit message. Many thanks! :)