There is a case that we attempt to allocate a hugepage with chg = 0 and
avoid_reserve = 1. Although chg = 0 means that it has a reserved hugepage,
we wouldn't use it, since avoid_reserve = 1 represents that we don't want
to allocate a hugepage from a reserved pool. This happens when the parent
process that created a MAP_PRIVATE mapping is about to perform a COW due to
a shared page count and it attempt to satisfy the allocation without using
the existing reserves.
In this case, we would not dequeue a reserved hugepage and, instead, try
to allocate a new hugepage. Therefore, we should check subpool counter
for a new hugepage. This patch implement it.
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
---
Replenishing commit message and adding reviewed-by tag.
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 12b6581..ea1ae0a 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1144,13 +1144,14 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
chg = vma_needs_reservation(h, vma, addr);
if (chg < 0)
return ERR_PTR(-ENOMEM);
- if (chg)
- if (hugepage_subpool_get_pages(spool, chg))
+ if (chg || avoid_reserve)
+ if (hugepage_subpool_get_pages(spool, 1))
return ERR_PTR(-ENOSPC);
ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), &h_cg);
if (ret) {
- hugepage_subpool_put_pages(spool, chg);
+ if (chg || avoid_reserve)
+ hugepage_subpool_put_pages(spool, 1);
return ERR_PTR(-ENOSPC);
}
spin_lock(&hugetlb_lock);
@@ -1162,7 +1163,8 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
hugetlb_cgroup_uncharge_cgroup(idx,
pages_per_huge_page(h),
h_cg);
- hugepage_subpool_put_pages(spool, chg);
+ if (chg || avoid_reserve)
+ hugepage_subpool_put_pages(spool, 1);
return ERR_PTR(-ENOSPC);
}
spin_lock(&hugetlb_lock);
--
1.7.9.5
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