mm/hugetlb: remove redundant reservation check condition in alloc_huge_page()
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Message ID 20210210075443.26238-1-linmiaohe@huawei.com
State Accepted
Commit 6501fe5f162395ba6dfa6ac86be05f1c24c1a7e0
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Series
  • mm/hugetlb: remove redundant reservation check condition in alloc_huge_page()
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Commit Message

Miaohe Lin Feb. 10, 2021, 7:54 a.m. UTC
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(-)

Comments

Mike Kravetz Feb. 13, 2021, 1:15 a.m. UTC | #1
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.
Miaohe Lin Feb. 18, 2021, 2:27 a.m. UTC | #2
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! :)

Patch
diff mbox series

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);