[RFC PATCH 09/14] mm: Handle large folios in free_unref_folios()

["Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>]

Call folio_undo_large_rmappable() if needed.  free_unref_page_prepare()
destroys the ability to call folio_order(), so stash the order in
folio->private for the benefit of the second loop.

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 mm/page_alloc.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index bca5c70b5576..e586d17fb7f2 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2465,7 +2465,7 @@ void free_unref_page(struct page *page, unsigned int order)
 }
 
 /*
- * Free a batch of 0-order pages
+ * Free a batch of folios
  */
 void free_unref_folios(struct folio_batch *folios)
 {
@@ -2478,7 +2478,11 @@ void free_unref_folios(struct folio_batch *folios)
 	for (i = 0, j = 0; i < folios->nr; i++) {
 		struct folio *folio = folios->folios[i];
 		unsigned long pfn = folio_pfn(folio);
-		if (!free_unref_page_prepare(&folio->page, pfn, 0))
+		unsigned int order = folio_order(folio);
+
+		if (order > 0 && folio_test_large_rmappable(folio))
+			folio_undo_large_rmappable(folio);
+		if (!free_unref_page_prepare(&folio->page, pfn, order))
 			continue;
 
 		/*
@@ -2486,11 +2490,13 @@ void free_unref_folios(struct folio_batch *folios)
 		 * comment in free_unref_page.
 		 */
 		migratetype = get_pcppage_migratetype(&folio->page);
-		if (unlikely(is_migrate_isolate(migratetype))) {
+		if (order > PAGE_ALLOC_COSTLY_ORDER ||
+		    is_migrate_isolate(migratetype)) {
 			free_one_page(folio_zone(folio), &folio->page, pfn,
-					0, migratetype, FPI_NONE);
+					order, migratetype, FPI_NONE);
 			continue;
 		}
+		folio->private = (void *)(unsigned long)order;
 		if (j != i)
 			folios->folios[j] = folio;
 		j++;
@@ -2500,7 +2506,9 @@ void free_unref_folios(struct folio_batch *folios)
 	for (i = 0; i < folios->nr; i++) {
 		struct folio *folio = folios->folios[i];
 		struct zone *zone = folio_zone(folio);
+		unsigned int order = (unsigned long)folio->private;
 
+		folio->private = NULL;
 		migratetype = get_pcppage_migratetype(&folio->page);
 
 		/* Different zone requires a different pcp lock */
@@ -2519,7 +2527,7 @@ void free_unref_folios(struct folio_batch *folios)
 			if (unlikely(!pcp)) {
 				pcp_trylock_finish(UP_flags);
 				free_one_page(zone, &folio->page,
-						folio_pfn(folio), 0,
+						folio_pfn(folio), order,
 						migratetype, FPI_NONE);
 				locked_zone = NULL;
 				continue;
@@ -2535,7 +2543,8 @@ void free_unref_folios(struct folio_batch *folios)
 			migratetype = MIGRATE_MOVABLE;
 
 		trace_mm_page_free_batched(&folio->page);
-		free_unref_page_commit(zone, pcp, &folio->page, migratetype, 0);
+		free_unref_page_commit(zone, pcp, &folio->page, migratetype,
+				order);
 	}
 
 	if (pcp) {
-- 
2.40.1