On Wed 02-12-15 23:12:40, Geliang Tang wrote:
> To make the intention clearer, use list_{first,last}_entry instead
> of list_entry.
I like list_{first,last}_entry that indeed helps readability, the
_or_null is less clear from the name, though. Previous check for an
empty list was easier to read, at least for me. But it seems like
this is a general pattern...
> Signed-off-by: Geliang Tang <geliangtang@xxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> mm/page_alloc.c | 23 +++++++++++------------
> 1 file changed, 11 insertions(+), 12 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index d6d7c97..0d38185 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -830,7 +830,7 @@ static void free_pcppages_bulk(struct zone *zone, int count,
> do {
> int mt; /* migratetype of the to-be-freed page */
>
> - page = list_entry(list->prev, struct page, lru);
> + page = list_last_entry(list, struct page, lru);
> /* must delete as __free_one_page list manipulates */
> list_del(&page->lru);
>
> @@ -1457,11 +1457,10 @@ struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
> /* Find a page of the appropriate size in the preferred list */
> for (current_order = order; current_order < MAX_ORDER; ++current_order) {
> area = &(zone->free_area[current_order]);
> - if (list_empty(&area->free_list[migratetype]))
> - continue;
> -
> - page = list_entry(area->free_list[migratetype].next,
> + page = list_first_entry_or_null(&area->free_list[migratetype],
> struct page, lru);
> + if (!page)
> + continue;
> list_del(&page->lru);
> rmv_page_order(page);
> area->nr_free--;
> @@ -1740,12 +1739,12 @@ static void unreserve_highatomic_pageblock(const struct alloc_context *ac)
> for (order = 0; order < MAX_ORDER; order++) {
> struct free_area *area = &(zone->free_area[order]);
>
> - if (list_empty(&area->free_list[MIGRATE_HIGHATOMIC]))
> + page = list_first_entry_or_null(
> + &area->free_list[MIGRATE_HIGHATOMIC],
> + struct page, lru);
> + if (!page)
> continue;
>
> - page = list_entry(area->free_list[MIGRATE_HIGHATOMIC].next,
> - struct page, lru);
> -
> /*
> * It should never happen but changes to locking could
> * inadvertently allow a per-cpu drain to add pages
> @@ -1793,7 +1792,7 @@ __rmqueue_fallback(struct zone *zone, unsigned int order, int start_migratetype)
> if (fallback_mt == -1)
> continue;
>
> - page = list_entry(area->free_list[fallback_mt].next,
> + page = list_first_entry(&area->free_list[fallback_mt],
> struct page, lru);
> if (can_steal)
> steal_suitable_fallback(zone, page, start_migratetype);
> @@ -2252,9 +2251,9 @@ struct page *buffered_rmqueue(struct zone *preferred_zone,
> }
>
> if (cold)
> - page = list_entry(list->prev, struct page, lru);
> + page = list_last_entry(list, struct page, lru);
> else
> - page = list_entry(list->next, struct page, lru);
> + page = list_first_entry(list, struct page, lru);
>
> list_del(&page->lru);
> pcp->count--;
> --
> 2.5.0
>
>
> --
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--
Michal Hocko
SUSE Labs
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