Re: [PATCH 3/3] mm/slab: use list_{empty_careful,last_entry} in drain_freelist

Christoph Lameter
2015-12-02T16:06:15Z

On Wed, 2 Dec 2015, Geliang Tang wrote:

> diff --git a/mm/slab.c b/mm/slab.c
> index 5d5aa3b..1a7d91c 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -2362,21 +2362,14 @@ static void drain_cpu_caches(struct kmem_cache *cachep)
> static int drain_freelist(struct kmem_cache *cache,
> struct kmem_cache_node *n, int tofree)
> {
> - struct list_head *p;
> int nr_freed;
> struct page *page;
>
> nr_freed = 0;
> - while (nr_freed < tofree && !list_empty(&n->slabs_free)) {
> + while (nr_freed < tofree && !list_empty_careful(&n->slabs_free)) {
>
> spin_lock_irq(&n->list_lock);
> - p = n->slabs_free.prev;
> - if (p == &n->slabs_free) {
> - spin_unlock_irq(&n->list_lock);
> - goto out;
> - }
> -
> - page = list_entry(p, struct page, lru);
> + page = list_last_entry(&n->slabs_free, struct page, lru);

This is safe? Process could be rescheduled and lots of things could happen
before disabling irqs.