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From:   Mike Kravetz <mike.kravetz@oracle.com>
To:     linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc:     Roman Gushchin <guro@fb.com>, Michal Hocko <mhocko@suse.com>,
        Shakeel Butt <shakeelb@google.com>,
        Oscar Salvador <osalvador@suse.de>,
        David Hildenbrand <david@redhat.com>,
        Muchun Song <songmuchun@bytedance.com>,
        David Rientjes <rientjes@google.com>,
        Miaohe Lin <linmiaohe@huawei.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Matthew Wilcox <willy@infradead.org>,
        HORIGUCHI NAOYA <naoya.horiguchi@nec.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
        Waiman Long <longman@redhat.com>, Peter Xu <peterx@redhat.com>,
        Mina Almasry <almasrymina@google.com>,
        Hillf Danton <hdanton@sina.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Barry Song <song.bao.hua@hisilicon.com>,
        Will Deacon <will@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mike Kravetz <mike.kravetz@oracle.com>
Subject: [PATCH v4 4/8] hugetlb: create remove_hugetlb_page() to separate functionality
Date:   Mon,  5 Apr 2021 16:00:39 -0700
Message-Id: <20210405230043.182734-5-mike.kravetz@oracle.com>
In-Reply-To: <20210405230043.182734-1-mike.kravetz@oracle.com>
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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.

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 mm/hugetlb.c | 88 ++++++++++++++++++++++++++++++----------------------
 1 file changed, 51 insertions(+), 37 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 8497a3598c86..df2a3d1f632b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1055,18 +1055,13 @@ static bool vma_has_reserves(struct vm_area_struct *vma, long chg)
 	return false;
 }
 
-static void __enqueue_huge_page(struct list_head *list, struct page *page)
-{
-	list_move(&page->lru, list);
-	SetHPageFreed(page);
-}
-
 static void enqueue_huge_page(struct hstate *h, struct page *page)
 {
 	int nid = page_to_nid(page);
-	__enqueue_huge_page(&h->hugepage_freelists[nid], page);
+	list_move(&page->lru, &h->hugepage_freelists[nid]);
 	h->free_huge_pages++;
 	h->free_huge_pages_node[nid]++;
+	SetHPageFreed(page);
 }
 
 static struct page *dequeue_huge_page_node_exact(struct hstate *h, int nid)
@@ -1331,6 +1326,43 @@ 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 +1371,6 @@ 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 +1378,6 @@ 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 +1445,12 @@ 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 +1735,7 @@ 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 +1773,6 @@ 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 +1803,7 @@ 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;
@@ -2298,6 +2312,7 @@ static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page,
 		/*
 		 * Freed from under us. Drop new_page too.
 		 */
+		remove_hugetlb_page(h, new_page, false);
 		update_and_free_page(h, new_page);
 		goto unlock;
 	} else if (page_count(old_page)) {
@@ -2305,6 +2320,7 @@ static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page,
 		 * Someone has grabbed the page, try to isolate it here.
 		 * Fail with -EBUSY if not possible.
 		 */
+		remove_hugetlb_page(h, new_page, false);
 		update_and_free_page(h, new_page);
 		spin_unlock(&hugetlb_lock);
 		if (!isolate_huge_page(old_page, list))
@@ -2323,13 +2339,13 @@ static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page,
 		/*
 		 * Ok, old_page is still a genuine free hugepage. Replace it
 		 * with the new one.
+		 * Note: h->free_huge_pages{_node} counters are decremented
+		 * in remove_hugetlb_page for old_page and incremented in
+		 * enqueue_huge_page for new page.  Net result is no change.
 		 */
-		list_del(&old_page->lru);
+		remove_hugetlb_page(h, old_page, false);
 		update_and_free_page(h, old_page);
-		/*
-		 * h->free_huge_pages{_node} counters do not need to be updated.
-		 */
-		__enqueue_huge_page(&h->hugepage_freelists[nid], new_page);
+		enqueue_huge_page(h, new_page);
 	}
 unlock:
 	spin_unlock(&hugetlb_lock);
@@ -2667,10 +2683,8 @@ 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