mm: refactor folio_undo_large_rmappable()

commit 593a10dabe upstream.

Folios of order <= 1 are not in deferred list, the check of order is added
into folio_undo_large_rmappable() from commit 8897277acf ("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/20240521130315.46072-1-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
[ Upstream commit itself does not apply cleanly, because there
  are fewer calls to folio_undo_large_rmappable() in this tree. ]
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

mm/huge_memory.c

@@ -2767,22 +2767,11 @@ out:
 	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

@@ -413,7 +413,22 @@ 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

@@ -600,9 +600,7 @@ void destroy_large_folio(struct folio *folio)
 		return;
 	}
 
-	if (folio_test_large_rmappable(folio))
-		folio_undo_large_rmappable(folio);
-
+	folio_undo_large_rmappable(folio);
 	mem_cgroup_uncharge(folio);
 	free_the_page(&folio->page, folio_order(folio));
 }