hugetlb: create remove_hugetlb_page() to separate functionality

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.

update_and_free_page no longer decrements h->nr_huge_pages{_node} as
this is performed in remove_hugetlb_page.  The only functionality
performed by update_and_free_page is to free the base pages to the lower
level allocators.

update_and_free_page is typically called after remove_hugetlb_page.

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.

Link: https://lkml.kernel.org/r/20210409205254.242291-5-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: HORIGUCHI NAOYA <naoya.horiguchi@nec.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/hugetlb.c

@@ -1333,6 +1333,41 @@ 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);
+
+	VM_BUG_ON_PAGE(hugetlb_cgroup_from_page(page), page);
+	VM_BUG_ON_PAGE(hugetlb_cgroup_from_page_rsvd(page), 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]--;
+	}
+	if (adjust_surplus) {
+		h->surplus_huge_pages--;
+		h->surplus_huge_pages_node[nid]--;
+	}
+
+	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;
@@ -1341,8 +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 |
@@ -1350,10 +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));
@@ -1421,15 +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);
@@ -1714,13 +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;
@@ -1758,7 +1778,6 @@ retry:
 	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;
 
@@ -1789,9 +1808,7 @@ retry:
 			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;
@@ -2558,10 +2575,8 @@ 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)]--;
 		}
 	}
 }