[PATCH] thp: deferred_split_scan(): stop shrinker if the queue is empty

[Kirill A. Shutemov]

If pages on queue were freed under us, deferred_split_scan() would
return zero. It makes caller keep calling deferred_split_scan() without
any result.

Let's return SHRINK_STOP in this situation.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Suggested-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
---
 mm/huge_memory.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 298dbc001b07..2ea5e26ce069 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3508,6 +3508,12 @@ static unsigned long deferred_split_scan(struct shrinker *shrink,
 	list_splice_tail(&list, &pgdata->split_queue);
 	spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
 
+	/*
+	 * Stop shrinker, if we didn't split any page, but the queue is empty.
+	 * This can happen if pages were freed under us.
+	 */
+	if (!split && list_empty(&pgdata->split_queue))
+		return SHRINK_STOP;
 	return split;
 }
 
-- 
 Kirill A. Shutemov