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SubjectRe: [PATCH v2] mm: memcontrol: replace the loop with a list_for_each_entry()
On Fri 05-02-21 00:30:55, Muchun Song wrote:
> 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>

Acked-by: Michal Hocko <mhocko@suse.com>

Thanks!

> ---
> 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

--
Michal Hocko
SUSE Labs

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