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 <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 8614e0d..fa7bf35 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5420,6 +5420,10 @@
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;