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Subject[PATCH 16/18] 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 bb8a45f..6a9ec69 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -649,6 +649,34 @@ struct hstate *size_to_hstate(unsigned long size)
return NULL;
}

+static void put_huge_page(struct page *page, int use_reserve)
+{
+ struct hstate *h = page_hstate(page);
+ struct hugepage_subpool *spool =
+ (struct hugepage_subpool *)page_private(page);
+
+ if (!use_reserve) {
+ put_page(page);
+ return;
+ }
+
+ if (!put_page_testzero(page))
+ return;
+
+ set_page_private(page, 0);
+ page->mapping = NULL;
+ BUG_ON(page_count(page));
+ BUG_ON(page_mapcount(page));
+
+ spin_lock(&hugetlb_lock);
+ hugetlb_cgroup_uncharge_page(hstate_index(h),
+ pages_per_huge_page(h), page);
+ enqueue_huge_page(h, page);
+ h->resv_huge_pages++;
+ spin_unlock(&hugetlb_lock);
+ hugepage_subpool_put_pages(spool, 1);
+}
+
static void free_huge_page(struct page *page)
{
/*
@@ -2625,7 +2653,7 @@ retry_avoidcopy:
spin_unlock(&mm->page_table_lock);
mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);

- page_cache_release(new_page);
+ put_huge_page(new_page, use_reserve);
out_old_page:
page_cache_release(old_page);
out_lock:
@@ -2725,7 +2753,7 @@ retry:

err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
if (err) {
- put_page(page);
+ put_huge_page(page, use_reserve);
if (err == -EEXIST)
goto retry;
goto out;
@@ -2798,7 +2826,7 @@ backout:
spin_unlock(&mm->page_table_lock);
backout_unlocked:
unlock_page(page);
- put_page(page);
+ put_huge_page(page, use_reserve);
goto out;
}

--
1.7.9.5


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