[PATCH v2 4/8] hugetlb: create remove_hugetlb_page() to separate functionality

[Mike Kravetz]

The new remove_hugetlb_page() routine is designed to remove a hugetlb
page from hugetlbfs processing.  It will remove the page from the active
or free list, update global counters and set the compound page
destructor to NULL so that PageHuge() will return false for the 'page'.
After this call, the 'page' can be treated as a normal compound page or
a collection of base size pages.

remove_hugetlb_page is to be called with the hugetlb_lock held.

Creating this routine and separating functionality is in preparation for
restructuring code to reduce lock hold times.  This commit should not
introduce any changes to functionality.

Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
 mm/hugetlb.c | 67 ++++++++++++++++++++++++++++++++--------------------
 1 file changed, 42 insertions(+), 25 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 8497a3598c86..16beabbbbe49 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1331,6 +1331,43 @@ static inline void destroy_compound_gigantic_page(struct page *page,
 						unsigned int order) { }
 #endif
 
+/*
+ * Remove hugetlb page from lists, and update dtor so that page appears
+ * as just a compound page.  A reference is held on the page.
+ *
+ * Must be called with hugetlb lock held.
+ */
+static void remove_hugetlb_page(struct hstate *h, struct page *page,
+							bool adjust_surplus)
+{
+	int nid = page_to_nid(page);
+
+	if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
+		return;
+
+	list_del(&page->lru);
+
+	if (HPageFreed(page)) {
+		h->free_huge_pages--;
+		h->free_huge_pages_node[nid]--;
+		ClearHPageFreed(page);
+	}
+	if (adjust_surplus) {
+		h->surplus_huge_pages--;
+		h->surplus_huge_pages_node[nid]--;
+	}
+
+	VM_BUG_ON_PAGE(hugetlb_cgroup_from_page(page), page);
+	VM_BUG_ON_PAGE(hugetlb_cgroup_from_page_rsvd(page), page);
+
+	ClearHPageTemporary(page);
+	set_page_refcounted(page);
+	set_compound_page_dtor(page, NULL_COMPOUND_DTOR);
+
+	h->nr_huge_pages--;
+	h->nr_huge_pages_node[nid]--;
+}
+
 static void update_and_free_page(struct hstate *h, struct page *page)
 {
 	int i;
@@ -1339,8 +1376,6 @@ static void update_and_free_page(struct hstate *h, struct page *page)
 	if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
 		return;
 
-	h->nr_huge_pages--;
-	h->nr_huge_pages_node[page_to_nid(page)]--;
 	for (i = 0; i < pages_per_huge_page(h);
 	     i++, subpage = mem_map_next(subpage, page, i)) {
 		subpage->flags &= ~(1 << PG_locked | 1 << PG_error |
@@ -1348,10 +1383,6 @@ static void update_and_free_page(struct hstate *h, struct page *page)
 				1 << PG_active | 1 << PG_private |
 				1 << PG_writeback);
 	}
-	VM_BUG_ON_PAGE(hugetlb_cgroup_from_page(page), page);
-	VM_BUG_ON_PAGE(hugetlb_cgroup_from_page_rsvd(page), page);
-	set_compound_page_dtor(page, NULL_COMPOUND_DTOR);
-	set_page_refcounted(page);
 	if (hstate_is_gigantic(h)) {
 		destroy_compound_gigantic_page(page, huge_page_order(h));
 		free_gigantic_page(page, huge_page_order(h));
@@ -1419,15 +1450,12 @@ static void __free_huge_page(struct page *page)
 		h->resv_huge_pages++;
 
 	if (HPageTemporary(page)) {
-		list_del(&page->lru);
-		ClearHPageTemporary(page);
+		remove_hugetlb_page(h, page, false);
 		update_and_free_page(h, page);
 	} else if (h->surplus_huge_pages_node[nid]) {
 		/* remove the page from active list */
-		list_del(&page->lru);
+		remove_hugetlb_page(h, page, true);
 		update_and_free_page(h, page);
-		h->surplus_huge_pages--;
-		h->surplus_huge_pages_node[nid]--;
 	} else {
 		arch_clear_hugepage_flags(page);
 		enqueue_huge_page(h, page);
@@ -1712,13 +1740,7 @@ static int free_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed,
 			struct page *page =
 				list_entry(h->hugepage_freelists[node].next,
 					  struct page, lru);
-			list_del(&page->lru);
-			h->free_huge_pages--;
-			h->free_huge_pages_node[node]--;
-			if (acct_surplus) {
-				h->surplus_huge_pages--;
-				h->surplus_huge_pages_node[node]--;
-			}
+			remove_hugetlb_page(h, page, acct_surplus);
 			update_and_free_page(h, page);
 			ret = 1;
 			break;
@@ -1756,7 +1778,6 @@ int dissolve_free_huge_page(struct page *page)
 	if (!page_count(page)) {
 		struct page *head = compound_head(page);
 		struct hstate *h = page_hstate(head);
-		int nid = page_to_nid(head);
 		if (h->free_huge_pages - h->resv_huge_pages == 0)
 			goto out;
 
@@ -1787,9 +1808,7 @@ int dissolve_free_huge_page(struct page *page)
 			SetPageHWPoison(page);
 			ClearPageHWPoison(head);
 		}
-		list_del(&head->lru);
-		h->free_huge_pages--;
-		h->free_huge_pages_node[nid]--;
+		remove_hugetlb_page(h, page, false);
 		h->max_huge_pages--;
 		update_and_free_page(h, head);
 		rc = 0;
@@ -2667,10 +2686,8 @@ static void try_to_free_low(struct hstate *h, unsigned long count,
 				return;
 			if (PageHighMem(page))
 				continue;
-			list_del(&page->lru);
+			remove_hugetlb_page(h, page, false);
 			update_and_free_page(h, page);
-			h->free_huge_pages--;
-			h->free_huge_pages_node[page_to_nid(page)]--;
 		}
 	}
 }
-- 
2.30.2