[PATCH v2 2/2] mm: hugetlb: support gigantic surplus pages

[Huang Shijie]

When testing the gigantic page whose order is too large for the buddy
allocator, the libhugetlbfs test case "counter.sh" will fail.

The failure is caused by:
 1) kernel fails to allocate a gigantic page for the surplus case.
    And the gather_surplus_pages() will return NULL in the end.

 2) The condition checks for "over-commit" is wrong.

This patch adds code to allocate the gigantic page in the
__alloc_huge_page(). After this patch, gather_surplus_pages()
can return a gigantic page for the surplus case.

This patch changes the condition checks for:
     return_unused_surplus_pages()
     nr_overcommit_hugepages_store()
     hugetlb_overcommit_handler()

This patch also set @nid with proper value when NUMA_NO_NODE is
passed to alloc_gigantic_page().

After this patch, the counter.sh can pass for the gigantic page.

Acked-by: Steve Capper <steve.capper at arm.com>
Signed-off-by: Huang Shijie <shijie.huang at arm.com>
---
  1. fix the wrong check in hugetlb_overcommit_handler();
  2. try to fix the s390 issue.
---
 mm/hugetlb.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 9fdfc24..5dbfd62 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1095,6 +1095,9 @@ static struct page *alloc_gigantic_page(int nid, unsigned int order)
 	unsigned long ret, pfn, flags;
 	struct zone *z;
 
+	if (nid == NUMA_NO_NODE)
+		nid = numa_mem_id();
+
 	z = NODE_DATA(nid)->node_zones;
 	for (; z - NODE_DATA(nid)->node_zones < MAX_NR_ZONES; z++) {
 		spin_lock_irqsave(&z->lock, flags);
@@ -1578,7 +1581,7 @@ static struct page *__alloc_huge_page(struct hstate *h,
 	struct page *page;
 	unsigned int r_nid;
 
-	if (hstate_is_gigantic(h))
+	if (hstate_is_gigantic(h) && !gigantic_page_supported())
 		return NULL;
 
 	/*
@@ -1623,7 +1626,13 @@ static struct page *__alloc_huge_page(struct hstate *h,
 	}
 	spin_unlock(&hugetlb_lock);
 
-	page = __hugetlb_alloc_buddy_huge_page(h, vma, addr, nid);
+	if (hstate_is_gigantic(h))  {
+		page = alloc_gigantic_page(nid, huge_page_order(h));
+		if (page)
+			prep_compound_gigantic_page(page, huge_page_order(h));
+	} else {
+		page = __hugetlb_alloc_buddy_huge_page(h, vma, addr, nid);
+	}
 
 	spin_lock(&hugetlb_lock);
 	if (page) {
@@ -1790,8 +1799,7 @@ static void return_unused_surplus_pages(struct hstate *h,
 	/* Uncommit the reservation */
 	h->resv_huge_pages -= unused_resv_pages;
 
-	/* Cannot return gigantic pages currently */
-	if (hstate_is_gigantic(h))
+	if (hstate_is_gigantic(h) && !gigantic_page_supported())
 		return;
 
 	nr_pages = min(unused_resv_pages, h->surplus_huge_pages);
@@ -2443,7 +2451,7 @@ static ssize_t nr_overcommit_hugepages_store(struct kobject *kobj,
 	unsigned long input;
 	struct hstate *h = kobj_to_hstate(kobj, NULL);
 
-	if (hstate_is_gigantic(h))
+	if (hstate_is_gigantic(h) && !gigantic_page_supported())
 		return -EINVAL;
 
 	err = kstrtoul(buf, 10, &input);
@@ -2884,7 +2892,7 @@ int hugetlb_overcommit_handler(struct ctl_table *table, int write,
 
 	tmp = h->nr_overcommit_huge_pages;
 
-	if (write && hstate_is_gigantic(h))
+	if (write && hstate_is_gigantic(h) && !gigantic_page_supported())
 		return -EINVAL;
 
 	table->data = &tmp;
-- 
2.1.4