mm: add folio dtor and order setter functions

Patch series "convert core hugetlb functions to folios", v5.

============== OVERVIEW ===========================
Now that many hugetlb helper functions that deal with hugetlb specific
flags[1] and hugetlb cgroups[2] are converted to folios, higher level
allocation, prep, and freeing functions within hugetlb can also be
converted to operate in folios.

Patch 1 of this series implements the wrapper functions around setting the
compound destructor and compound order for a folio.  Besides the user
added in patch 1, patch 2 and patch 9 also use these helper functions.

Patches 2-10 convert the higher level hugetlb functions to folios.

============== TESTING ===========================
LTP:
	Ran 10 back to back rounds of the LTP hugetlb test suite.

Gigantic Huge Pages:
	Test allocation and freeing via hugeadm commands:
		hugeadm --pool-pages-min 1GB:10
		hugeadm --pool-pages-min 1GB:0

Demote:
	Demote 1 1GB hugepages to 512 2MB hugepages
		echo 1 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages
		echo 1 > /sys/kernel/mm/hugepages/hugepages-1048576kB/demote
		cat /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
			# 512
		cat /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages
			# 0

[1] https://lore.kernel.org/lkml/20220922154207.1575343-1-sidhartha.kumar@oracle.com/
[2] https://lore.kernel.org/linux-mm/20221101223059.460937-1-sidhartha.kumar@oracle.com/


This patch (of 10):

Add folio equivalents for set_compound_order() and
set_compound_page_dtor().

Also remove extra new-lines introduced by mm/hugetlb: convert
move_hugetlb_state() to folios and mm/hugetlb_cgroup: convert
hugetlb_cgroup_uncharge_page() to folios.

[sidhartha.kumar@oracle.com: clarify folio_set_compound_order() zero support]
  Link: https://lkml.kernel.org/r/20221207223731.32784-1-sidhartha.kumar@oracle.com
Link: https://lkml.kernel.org/r/20221129225039.82257-1-sidhartha.kumar@oracle.com
Link: https://lkml.kernel.org/r/20221129225039.82257-2-sidhartha.kumar@oracle.comSigned-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Suggested-by: Mike Kravetz <mike.kravetz@oracle.com>
Suggested-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Tarun Sahu <tsahu@linux.ibm.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Wei Chen <harperchen1110@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/mm.h

@@ -997,6 +997,13 @@ static inline void set_compound_page_dtor(struct page *page,
 	page[1].compound_dtor = compound_dtor;
 }
 
+static inline void folio_set_compound_dtor(struct folio *folio,
+		enum compound_dtor_id compound_dtor)
+{
+	VM_BUG_ON_FOLIO(compound_dtor >= NR_COMPOUND_DTORS, folio);
+	folio->_folio_dtor = compound_dtor;
+}
+
 void destroy_large_folio(struct folio *folio);
 
 static inline int head_compound_pincount(struct page *head)
@@ -1012,6 +1019,22 @@ static inline void set_compound_order(struct page *page, unsigned int order)
 #endif
 }
 
+/*
+ * folio_set_compound_order is generally passed a non-zero order to
+ * initialize a large folio.  However, hugetlb code abuses this by
+ * passing in zero when 'dissolving' a large folio.
+ */
+static inline void folio_set_compound_order(struct folio *folio,
+		unsigned int order)
+{
+	VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
+
+	folio->_folio_order = order;
+#ifdef CONFIG_64BIT
+	folio->_folio_nr_pages = order ? 1U << order : 0;
+#endif
+}
+
 /* Returns the number of pages in this potentially compound page. */
 static inline unsigned long compound_nr(struct page *page)
 {

mm/hugetlb.c

@@ -1780,7 +1780,7 @@ static void __prep_new_hugetlb_folio(struct hstate *h, struct folio *folio)
 {
 	hugetlb_vmemmap_optimize(h, &folio->page);
 	INIT_LIST_HEAD(&folio->lru);
-	folio->_folio_dtor = HUGETLB_PAGE_DTOR;
+	folio_set_compound_dtor(folio, HUGETLB_PAGE_DTOR);
 	hugetlb_set_folio_subpool(folio, NULL);
 	set_hugetlb_cgroup(folio, NULL);
 	set_hugetlb_cgroup_rsvd(folio, NULL);
@@ -2938,7 +2938,6 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
 	 * a reservation exists for the allocation.
 	 */
 	page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve, gbl_chg);
-
 	if (!page) {
 		spin_unlock_irq(&hugetlb_lock);
 		page = alloc_buddy_huge_page_with_mpol(h, vma, addr);
@@ -7343,7 +7342,6 @@ void move_hugetlb_state(struct folio *old_folio, struct folio *new_folio, int re
 		int old_nid = folio_nid(old_folio);
 		int new_nid = folio_nid(new_folio);
 
-
 		folio_set_hugetlb_temporary(old_folio);
 		folio_clear_hugetlb_temporary(new_folio);