mm: change the interface of prep_compound_tail()

Instead of passing down the head page and tail page index, pass the tail
and head pages directly, as well as the order of the compound page.

This is a preparation for changing how the head position is encoded in the
tail page.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Kiryl Shutsemau <[email protected]>
Reviewed-by: Muchun Song <[email protected]>
Reviewed-by: Zi Yan <[email protected]>
Acked-by: David Hildenbrand (arm) <[email protected]>
Reviewed-by: Vlastimil Babka <[email protected]>
Cc: Albert Ou <[email protected]>
Cc: Alexandre Ghiti <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Frank van der Linden <[email protected]>
Cc: Harry Yoo <[email protected]>
Cc: Huacai Chen <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Oscar Salvador <[email protected]>
Cc: Palmer Dabbelt <[email protected]>
Cc: Paul Walmsley <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Usama Arif <[email protected]>
Cc: WANG Xuerui <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

include/linux/page-flags.h

@@ -870,9 +870,10 @@ static inline bool folio_test_large(const struct folio *folio)
 	return folio_test_head(folio);
 }
 
-static __always_inline void set_compound_head(struct page *page, struct page *head)
+static __always_inline void set_compound_head(struct page *tail,
+		const struct page *head, unsigned int order)
 {
-	WRITE_ONCE(page->compound_head, (unsigned long)head + 1);
+	WRITE_ONCE(tail->compound_head, (unsigned long)head + 1);
 }
 
 static __always_inline void clear_compound_head(struct page *page)

mm/hugetlb.c

@@ -3168,6 +3168,7 @@ found:
 
 /* Initialize [start_page:end_page_number] tail struct pages of a hugepage */
 static void __init hugetlb_folio_init_tail_vmemmap(struct folio *folio,
+					struct hstate *h,
 					unsigned long start_page_number,
 					unsigned long end_page_number)
 {
@@ -3176,6 +3177,7 @@ static void __init hugetlb_folio_init_tail_vmemmap(struct folio *folio,
 	struct page *page = folio_page(folio, start_page_number);
 	unsigned long head_pfn = folio_pfn(folio);
 	unsigned long pfn, end_pfn = head_pfn + end_page_number;
+	unsigned int order = huge_page_order(h);
 
 	/*
 	 * As we marked all tail pages with memblock_reserved_mark_noinit(),
@@ -3183,7 +3185,7 @@ static void __init hugetlb_folio_init_tail_vmemmap(struct folio *folio,
 	 */
 	for (pfn = head_pfn + start_page_number; pfn < end_pfn; page++, pfn++) {
 		__init_single_page(page, pfn, zone, nid);
-		prep_compound_tail((struct page *)folio, pfn - head_pfn);
+		prep_compound_tail(page, &folio->page, order);
 		set_page_count(page, 0);
 	}
 }
@@ -3203,7 +3205,7 @@ static void __init hugetlb_folio_init_vmemmap(struct folio *folio,
 	__folio_set_head(folio);
 	ret = folio_ref_freeze(folio, 1);
 	VM_BUG_ON(!ret);
-	hugetlb_folio_init_tail_vmemmap(folio, 1, nr_pages);
+	hugetlb_folio_init_tail_vmemmap(folio, h, 1, nr_pages);
 	prep_compound_head(&folio->page, huge_page_order(h));
 }
 
@@ -3260,7 +3262,7 @@ static void __init prep_and_add_bootmem_folios(struct hstate *h,
 			 * time as this is early in boot and there should
 			 * be no contention.
 			 */
-			hugetlb_folio_init_tail_vmemmap(folio,
+			hugetlb_folio_init_tail_vmemmap(folio, h,
 					HUGETLB_VMEMMAP_RESERVE_PAGES,
 					pages_per_huge_page(h));
 		}

mm/internal.h

@@ -897,13 +897,12 @@ static inline void prep_compound_head(struct page *page, unsigned int order)
 		INIT_LIST_HEAD(&folio->_deferred_list);
 }
 
-static inline void prep_compound_tail(struct page *head, int tail_idx)
+static inline void prep_compound_tail(struct page *tail,
+		const struct page *head, unsigned int order)
 {
-	struct page *p = head + tail_idx;
-
-	p->mapping = TAIL_MAPPING;
-	set_compound_head(p, head);
-	set_page_private(p, 0);
+	tail->mapping = TAIL_MAPPING;
+	set_compound_head(tail, head, order);
+	set_page_private(tail, 0);
 }
 
 void post_alloc_hook(struct page *page, unsigned int order, gfp_t gfp_flags);

mm/mm_init.c

@@ -1110,7 +1110,7 @@ static void __ref memmap_init_compound(struct page *head,
 		struct page *page = pfn_to_page(pfn);
 
 		__init_zone_device_page(page, pfn, zone_idx, nid, pgmap);
-		prep_compound_tail(head, pfn - head_pfn);
+		prep_compound_tail(page, head, order);
 		set_page_count(page, 0);
 	}
 	prep_compound_head(head, order);

mm/page_alloc.c

@@ -744,7 +744,7 @@ void prep_compound_page(struct page *page, unsigned int order)
 
 	__SetPageHead(page);
 	for (i = 1; i < nr_pages; i++)
-		prep_compound_tail(page, i);
+		prep_compound_tail(page + i, page, order);
 
 	prep_compound_head(page, order);
 }