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Subject[PATCH v2 06/20] mm, hugetlb: return a reserved page to a reserved pool if failed
Date
If we fail with a reserved page, just calling put_page() is not sufficient,
because put_page() invoke free_huge_page() at last step and it doesn't
know whether a page comes from a reserved pool or not. So it doesn't do
anything related to reserved count. This makes reserve count lower
than how we need, because reserve count already decrease in
dequeue_huge_page_vma(). This patch fix this situation.

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

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 6c8eec2..3f834f1 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -572,6 +572,7 @@ retry_cpuset:
if (!vma_has_reserves(vma, chg))
break;

+ SetPagePrivate(page);
h->resv_huge_pages--;
break;
}
@@ -626,15 +627,20 @@ static void free_huge_page(struct page *page)
int nid = page_to_nid(page);
struct hugepage_subpool *spool =
(struct hugepage_subpool *)page_private(page);
+ bool restore_reserve;

set_page_private(page, 0);
page->mapping = NULL;
BUG_ON(page_count(page));
BUG_ON(page_mapcount(page));
+ restore_reserve = PagePrivate(page);

spin_lock(&hugetlb_lock);
hugetlb_cgroup_uncharge_page(hstate_index(h),
pages_per_huge_page(h), page);
+ if (restore_reserve)
+ h->resv_huge_pages++;
+
if (h->surplus_huge_pages_node[nid] && huge_page_order(h) < MAX_ORDER) {
/* remove the page from active list */
list_del(&page->lru);
@@ -2616,6 +2622,8 @@ retry_avoidcopy:
spin_lock(&mm->page_table_lock);
ptep = huge_pte_offset(mm, address & huge_page_mask(h));
if (likely(pte_same(huge_ptep_get(ptep), pte))) {
+ ClearPagePrivate(new_page);
+
/* Break COW */
huge_ptep_clear_flush(vma, address, ptep);
set_huge_pte_at(mm, address, ptep,
@@ -2727,6 +2735,7 @@ retry:
goto retry;
goto out;
}
+ ClearPagePrivate(page);

spin_lock(&inode->i_lock);
inode->i_blocks += blocks_per_huge_page(h);
@@ -2773,8 +2782,10 @@ retry:
if (!huge_pte_none(huge_ptep_get(ptep)))
goto backout;

- if (anon_rmap)
+ if (anon_rmap) {
+ ClearPagePrivate(page);
hugepage_add_new_anon_rmap(page, vma, address);
+ }
else
page_dup_rmap(page);
new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
--
1.7.9.5


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