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Subject[PATCH v2 16/20] mm, hugetlb: move down outside_reserve check
Date
Just move down outside_reserve check and don't check
vma_need_reservation() when outside_resever is true. It is slightly
optimized implementation.

This makes code more readable.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 24de2ca..2372f75 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2499,7 +2499,7 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
struct page *old_page, *new_page;
int outside_reserve = 0;
long chg;
- bool use_reserve;
+ bool use_reserve = false;
unsigned long mmun_start; /* For mmu_notifiers */
unsigned long mmun_end; /* For mmu_notifiers */

@@ -2514,6 +2514,11 @@ retry_avoidcopy:
return 0;
}

+ page_cache_get(old_page);
+
+ /* Drop page_table_lock as buddy allocator may be called */
+ spin_unlock(&mm->page_table_lock);
+
/*
* If the process that created a MAP_PRIVATE mapping is about to
* perform a COW due to a shared page count, attempt to satisfy
@@ -2527,19 +2532,17 @@ retry_avoidcopy:
old_page != pagecache_page)
outside_reserve = 1;

- page_cache_get(old_page);
-
- /* Drop page_table_lock as buddy allocator may be called */
- spin_unlock(&mm->page_table_lock);
- chg = vma_needs_reservation(h, vma, address);
- if (chg == -ENOMEM) {
- page_cache_release(old_page);
+ if (!outside_reserve) {
+ chg = vma_needs_reservation(h, vma, address);
+ if (chg == -ENOMEM) {
+ page_cache_release(old_page);

- /* Caller expects lock to be held */
- spin_lock(&mm->page_table_lock);
- return VM_FAULT_OOM;
+ /* Caller expects lock to be held */
+ spin_lock(&mm->page_table_lock);
+ return VM_FAULT_OOM;
+ }
+ use_reserve = !chg;
}
- use_reserve = !chg && !outside_reserve;

new_page = alloc_huge_page(vma, address, use_reserve);

--
1.7.9.5


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