| Message ID | 20210204105320.46072-1-songmuchun@bytedance.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm: memcontrol: replace the loop with a list_for_each_entry() | expand |
On Thu, Feb 04, 2021 at 06:53:20PM +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(). > > Signed-off-by: Muchun Song <songmuchun@bytedance.com> > --- > mm/memcontrol.c | 17 ++--------------- > 1 file changed, 2 insertions(+), 15 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 6c7f1ea3955e..43341bd7ea1c 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -6891,24 +6891,11 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug) > static void uncharge_list(struct list_head *page_list) > { > struct uncharge_gather ug; > - struct list_head *next; > + struct page *page; > > 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; > - > + list_for_each_entry(page, page_list, lru) > uncharge_page(page, &ug); > - } while (next != page_list); > - > uncharge_batch(&ug); Good catch, this makes things much simpler. Looking at the surrounding code, there also seems to be no reason anymore to have uncharge_list() as a separate function: there is only one caller after the mentioned commit, and it's trivial after your change. Would you mind folding it into mem_cgroup_uncharge_list()? The list_empty() check in that one is also unnecessary now: the do-while loop required at least one page to be on the list or it would crash, but list_for_each() will be just fine on an empty list. Thanks
On Thu, Feb 4, 2021 at 11:14 PM Johannes Weiner <hannes@cmpxchg.org> wrote: > > On Thu, Feb 04, 2021 at 06:53:20PM +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(). > > > > Signed-off-by: Muchun Song <songmuchun@bytedance.com> > > --- > > mm/memcontrol.c | 17 ++--------------- > > 1 file changed, 2 insertions(+), 15 deletions(-) > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 6c7f1ea3955e..43341bd7ea1c 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -6891,24 +6891,11 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug) > > static void uncharge_list(struct list_head *page_list) > > { > > struct uncharge_gather ug; > > - struct list_head *next; > > + struct page *page; > > > > 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; > > - > > + list_for_each_entry(page, page_list, lru) > > uncharge_page(page, &ug); > > - } while (next != page_list); > > - > > uncharge_batch(&ug); > > Good catch, this makes things much simpler. > > Looking at the surrounding code, there also seems to be no reason > anymore to have uncharge_list() as a separate function: there is only > one caller after the mentioned commit, and it's trivial after your > change. Would you mind folding it into mem_cgroup_uncharge_list()? Will do. Thanks. > > The list_empty() check in that one is also unnecessary now: the > do-while loop required at least one page to be on the list or it would > crash, but list_for_each() will be just fine on an empty list. Right. It makes things more simple. > > Thanks
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 6c7f1ea3955e..43341bd7ea1c 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -6891,24 +6891,11 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug) static void uncharge_list(struct list_head *page_list) { struct uncharge_gather ug; - struct list_head *next; + struct page *page; 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; - + list_for_each_entry(page, page_list, lru) uncharge_page(page, &ug); - } while (next != page_list); - uncharge_batch(&ug); }
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(). Signed-off-by: Muchun Song <songmuchun@bytedance.com> --- mm/memcontrol.c | 17 ++--------------- 1 file changed, 2 insertions(+), 15 deletions(-)