From 8b5926560fafe80fe764af2aade152d490a96546 Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Thu, 17 Mar 2016 14:20:31 -0700 Subject: [PATCH] mm: memcontrol: clarify the uncharge_list() loop uncharge_list() does an unusual list walk because the function can take regular lists with dedicated list_heads as well as singleton lists where a single page is passed via the page->lru list node. This can sometimes lead to confusion as well as suggestions to replace the loop with a list_for_each_entry(), which wouldn't work. Signed-off-by: Johannes Weiner Acked-by: Michal Hocko Cc: Vladimir Davydov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 8614e0d750e5..fa7bf354ae32 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5420,6 +5420,10 @@ static void uncharge_list(struct list_head *page_list) struct list_head *next; struct page *page; + /* + * Note that the list can be a single page->lru; hence the + * do-while loop instead of a simple list_for_each_entry(). + */ next = page_list->next; do { unsigned int nr_pages = 1; -- 2.20.1