On Thu 10-03-16 15:50:15, Johannes Weiner wrote:
> 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.
Yes this confused at least me 2 times AFAIR.
>
> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Thanks!
> ---
> 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;
> --
> 2.7.2
--
Michal Hocko
SUSE Labs
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