2021-02-04 16:37:55

by Muchun Song

Subject: [PATCH v2] mm: memcontrol: replace the loop with a list_for_each_entry()

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 <[email protected]>
---
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

2021-02-04 17:47:37

by Johannes Weiner

Subject: Re: [PATCH v2] mm: memcontrol: replace the loop with a list_for_each_entry()

On Fri, Feb 05, 2021 at 12:30:55AM +0800, 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 <[email protected]>

Acked-by: Johannes Weiner <[email protected]>

Thank you, Muchun!

2021-02-05 01:32:40

by Roman Gushchin

Subject: Re: [PATCH v2] mm: memcontrol: replace the loop with a list_for_each_entry()

On Fri, Feb 05, 2021 at 12:30:55AM +0800, 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 <[email protected]>
> ---
> v2:
> - Fold uncharge_list() to mem_cgroup_uncharge_list().
>
> mm/memcontrol.c | 35 ++++++++---------------------------
> 1 file changed, 8 insertions(+), 27 deletions(-)

Nice cleanup!

Acked-by: Roman Gushchin <[email protected]>

Thanks.

2021-02-05 02:57:04

by Miaohe Lin

Subject: Re: [PATCH v2] mm: memcontrol: replace the loop with a list_for_each_entry()

Hi:
On 2021/2/5 0:30, 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 <[email protected]>

LGTM. Thanks.
Reviewed-by: Miaohe Lin <[email protected]>

> ---
> 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);
> }
>
> /**
>

2021-02-05 23:23:40

by Michal Hocko

Subject: Re: [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 <[email protected]>

Acked-by: Michal Hocko <[email protected]>

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

2021-02-06 04:13:24

by Shakeel Butt

Subject: Re: [PATCH v2] mm: memcontrol: replace the loop with a list_for_each_entry()

On Thu, Feb 4, 2021 at 8:39 AM Muchun Song <[email protected]> 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 <[email protected]>

Reviewed-by: Shakeel Butt <[email protected]>