mm: refactor folio_undo_large_rmappable()

Folios of order <= 1 are not in deferred list, the check of order is added
into folio_undo_large_rmappable() from commit 8897277 ("mm: support
order-1 folios in the page cache"), but there is a repeated check for
small folio (order 0) during each call of the
folio_undo_large_rmappable(), so only keep folio_order() check inside the
function.

In addition, move all the checks into header file to save a function call
for non-large-rmappable or empty deferred_list folio.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Kefeng Wang <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Reviewed-by: Vishal Moola (Oracle) <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Lance Yang <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Shakeel Butt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: Kefeng Wang

mm/huge_memory.c

@@ -3258,22 +3258,11 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
 	return ret;
 }
 
-void folio_undo_large_rmappable(struct folio *folio)
+void __folio_undo_large_rmappable(struct folio *folio)
 {
 	struct deferred_split *ds_queue;
 	unsigned long flags;
 
-	if (folio_order(folio) <= 1)
-		return;
-
-	/*
-	 * At this point, there is no one trying to add the folio to
-	 * deferred_list. If folio is not in deferred_list, it's safe
-	 * to check without acquiring the split_queue_lock.
-	 */
-	if (data_race(list_empty(&folio->_deferred_list)))
-		return;
-
 	ds_queue = get_deferred_split_queue(folio);
 	spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
 	if (!list_empty(&folio->_deferred_list)) {

mm/internal.h

@@ -622,7 +622,22 @@ static inline void folio_set_order(struct folio *folio, unsigned int order)
 #endif
 }
 
-void folio_undo_large_rmappable(struct folio *folio);
+void __folio_undo_large_rmappable(struct folio *folio);
+static inline void folio_undo_large_rmappable(struct folio *folio)
+{
+	if (folio_order(folio) <= 1 || !folio_test_large_rmappable(folio))
+		return;
+
+	/*
+	 * At this point, there is no one trying to add the folio to
+	 * deferred_list. If folio is not in deferred_list, it's safe
+	 * to check without acquiring the split_queue_lock.
+	 */
+	if (data_race(list_empty(&folio->_deferred_list)))
+		return;
+
+	__folio_undo_large_rmappable(folio);
+}
 
 static inline struct folio *page_rmappable_folio(struct page *page)
 {

mm/page_alloc.c

@@ -2661,8 +2661,7 @@ void free_unref_folios(struct folio_batch *folios)
 		unsigned long pfn = folio_pfn(folio);
 		unsigned int order = folio_order(folio);
 
-		if (order > 0 && folio_test_large_rmappable(folio))
-			folio_undo_large_rmappable(folio);
+		folio_undo_large_rmappable(folio);
 		if (!free_pages_prepare(&folio->page, order))
 			continue;
 		/*

mm/swap.c

@@ -123,8 +123,7 @@ void __folio_put(struct folio *folio)
 	}
 
 	page_cache_release(folio);
-	if (folio_test_large(folio) && folio_test_large_rmappable(folio))
-		folio_undo_large_rmappable(folio);
+	folio_undo_large_rmappable(folio);
 	mem_cgroup_uncharge(folio);
 	free_unref_page(&folio->page, folio_order(folio));
 }
@@ -1002,10 +1001,7 @@ void folios_put_refs(struct folio_batch *folios, unsigned int *refs)
 			free_huge_folio(folio);
 			continue;
 		}
-		if (folio_test_large(folio) &&
-		    folio_test_large_rmappable(folio))
-			folio_undo_large_rmappable(folio);
-
+		folio_undo_large_rmappable(folio);
 		__page_cache_release(folio, &lruvec, &flags);
 
 		if (j != i)

mm/vmscan.c

@@ -1439,9 +1439,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list,
 		 */
 		nr_reclaimed += nr_pages;
 
-		if (folio_test_large(folio) &&
-		    folio_test_large_rmappable(folio))
-			folio_undo_large_rmappable(folio);
+		folio_undo_large_rmappable(folio);
 		if (folio_batch_add(&free_folios, folio) == 0) {
 			mem_cgroup_uncharge_folios(&free_folios);
 			try_to_unmap_flush();
@@ -1848,9 +1846,7 @@ static unsigned int move_folios_to_lru(struct lruvec *lruvec,
 		if (unlikely(folio_put_testzero(folio))) {
 			__folio_clear_lru_flags(folio);
 
-			if (folio_test_large(folio) &&
-			    folio_test_large_rmappable(folio))
-				folio_undo_large_rmappable(folio);
+			folio_undo_large_rmappable(folio);
 			if (folio_batch_add(&free_folios, folio) == 0) {
 				spin_unlock_irq(&lruvec->lru_lock);
 				mem_cgroup_uncharge_folios(&free_folios);