mm: remove HUGETLB_PAGE_DTOR

We can use a bit in page[1].flags to indicate that this folio belongs to
hugetlb instead of using a value in page[1].dtors.  That lets
folio_test_hugetlb() become an inline function like it should be.  We can
also get rid of NULL_COMPOUND_DTOR.

Link: https://lkml.kernel.org/r/20230816151201.3655946-8-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Yanteng Si <siyanteng@loongson.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

2 files changed, 7 insertions, 44 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 6a3c80026ab3..a82c3104337e 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1585,25 +1585,7 @@ static inline void __clear_hugetlb_destructor(struct hstate *h,
 {
 	lockdep_assert_held(&hugetlb_lock);
 
-	/*
-	 * Very subtle
-	 *
-	 * For non-gigantic pages set the destructor to the normal compound
-	 * page dtor.  This is needed in case someone takes an additional
-	 * temporary ref to the page, and freeing is delayed until they drop
-	 * their reference.
-	 *
-	 * For gigantic pages set the destructor to the null dtor.  This
-	 * destructor will never be called.  Before freeing the gigantic
-	 * page destroy_compound_gigantic_folio will turn the folio into a
-	 * simple group of pages.  After this the destructor does not
-	 * apply.
-	 *
-	 */
-	if (hstate_is_gigantic(h))
-		folio_set_compound_dtor(folio, NULL_COMPOUND_DTOR);
-	else
-		folio_set_compound_dtor(folio, COMPOUND_PAGE_DTOR);
+	folio_clear_hugetlb(folio);
 }
 
 /*
@@ -1690,7 +1672,7 @@ static void add_hugetlb_folio(struct hstate *h, struct folio *folio,
 		h->surplus_huge_pages_node[nid]++;
 	}
 
-	folio_set_compound_dtor(folio, HUGETLB_PAGE_DTOR);
+	folio_set_hugetlb(folio);
 	folio_change_private(folio, NULL);
 	/*
 	 * We have to set hugetlb_vmemmap_optimized again as above
@@ -1814,9 +1796,8 @@ static void free_hpage_workfn(struct work_struct *work)
 		/*
 		 * The VM_BUG_ON_FOLIO(!folio_test_hugetlb(folio), folio) in
 		 * folio_hstate() is going to trigger because a previous call to
-		 * remove_hugetlb_folio() will call folio_set_compound_dtor
-		 * (folio, NULL_COMPOUND_DTOR), so do not use folio_hstate()
-		 * directly.
+		 * remove_hugetlb_folio() will clear the hugetlb bit, so do
+		 * not use folio_hstate() directly.
 		 */
 		h = size_to_hstate(page_size(page));
 
@@ -1955,7 +1936,7 @@ static void __prep_new_hugetlb_folio(struct hstate *h, struct folio *folio)
 {
 	hugetlb_vmemmap_optimize(h, &folio->page);
 	INIT_LIST_HEAD(&folio->lru);
-	folio_set_compound_dtor(folio, HUGETLB_PAGE_DTOR);
+	folio_set_hugetlb(folio);
 	hugetlb_set_folio_subpool(folio, NULL);
 	set_hugetlb_cgroup(folio, NULL);
 	set_hugetlb_cgroup_rsvd(folio, NULL);
@@ -2070,28 +2051,10 @@ int PageHuge(struct page *page)
 	if (!PageCompound(page))
 		return 0;
 	folio = page_folio(page);
-	return folio->_folio_dtor == HUGETLB_PAGE_DTOR;
+	return folio_test_hugetlb(folio);
 }
 EXPORT_SYMBOL_GPL(PageHuge);
 
-/**
- * folio_test_hugetlb - Determine if the folio belongs to hugetlbfs
- * @folio: The folio to test.
- *
- * Context: Any context.  Caller should have a reference on the folio to
- * prevent it from being turned into a tail page.
- * Return: True for hugetlbfs folios, false for anon folios or folios
- * belonging to other filesystems.
- */
-bool folio_test_hugetlb(struct folio *folio)
-{
-	if (!folio_test_large(folio))
-		return false;
-
-	return folio->_folio_dtor == HUGETLB_PAGE_DTOR;
-}
-EXPORT_SYMBOL_GPL(folio_test_hugetlb);
-
 /*
  * Find and lock address space (mapping) in write mode.
  *
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 31fec31be31e..d96dc6a3077a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1112,7 +1112,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
 		VM_BUG_ON_PAGE(compound && compound_order(page) != order, page);
 
 		if (compound)
-			ClearPageHasHWPoisoned(page);
+			page[1].flags &= ~PAGE_FLAGS_SECOND;
 		for (i = 1; i < (1 << order); i++) {
 			if (compound)
 				bad += free_tail_page_prepare(page, page + i);