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Subject[PATCH v2] mm: memcontrol: replace the loop with a list_for_each_entry()
Date
The rule of list walk has gone since:

commit a9d5adeeb4b2 ("mm/memcontrol: allow to uncharge page without using page->lru field")

So remove the strange comment and replace the loop with a
list_for_each_entry().

There is only one caller of the uncharge_list(). So just fold it into
mem_cgroup_uncharge_list() and remove it.

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
v2:
- Fold uncharge_list() to mem_cgroup_uncharge_list().

mm/memcontrol.c | 35 ++++++++---------------------------
1 file changed, 8 insertions(+), 27 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ed5cc78a8dbf..8c035846c7a4 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6862,31 +6862,6 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug)
css_put(&ug->memcg->css);
}

-static void uncharge_list(struct list_head *page_list)
-{
- struct uncharge_gather ug;
- struct list_head *next;
-
- uncharge_gather_clear(&ug);
-
- /*
- * 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 {
- struct page *page;
-
- page = list_entry(next, struct page, lru);
- next = page->lru.next;
-
- uncharge_page(page, &ug);
- } while (next != page_list);
-
- if (ug.memcg)
- uncharge_batch(&ug);
-}
-
/**
* mem_cgroup_uncharge - uncharge a page
* @page: page to uncharge
@@ -6918,11 +6893,17 @@ void mem_cgroup_uncharge(struct page *page)
*/
void mem_cgroup_uncharge_list(struct list_head *page_list)
{
+ struct uncharge_gather ug;
+ struct page *page;
+
if (mem_cgroup_disabled())
return;

- if (!list_empty(page_list))
- uncharge_list(page_list);
+ uncharge_gather_clear(&ug);
+ list_for_each_entry(page, page_list, lru)
+ uncharge_page(page, &ug);
+ if (ug.memcg)
+ uncharge_batch(&ug);
}

/**
--
2.11.0
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