From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
rcu_head may now grow larger than list_head without affecting slab or
slub.
Signed-off-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
Acked-by: Christoph Lameter <cl@xxxxxxxxx>
---
mm/slab.c | 2 --
mm/slub.c | 27 ++-------------------------
2 files changed, 2 insertions(+), 27 deletions(-)
diff --git a/mm/slab.c b/mm/slab.c
index e387a17d6d56..e6ab1327db25 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1235,8 +1235,6 @@ void __init kmem_cache_init(void)
{
int i;
- BUILD_BUG_ON(sizeof(((struct page *)NULL)->lru) <
- sizeof(struct rcu_head));
kmem_cache = &kmem_cache_boot;
if (!IS_ENABLED(CONFIG_NUMA) || num_possible_nodes() == 1)
diff --git a/mm/slub.c b/mm/slub.c
index 57a20f995220..8e2407f69855 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1681,17 +1681,9 @@ static void __free_slab(struct kmem_cache *s, struct page *page)
__free_pages(page, order);
}
-#define need_reserve_slab_rcu \
- (sizeof(((struct page *)NULL)->lru) < sizeof(struct rcu_head))
-
static void rcu_free_slab(struct rcu_head *h)
{
- struct page *page;
-
- if (need_reserve_slab_rcu)
- page = virt_to_head_page(h);
- else
- page = container_of((struct list_head *)h, struct page, lru);
+ struct page *page = container_of(h, struct page, rcu_head);
__free_slab(page->slab_cache, page);
}
@@ -1699,19 +1691,7 @@ static void rcu_free_slab(struct rcu_head *h)
static void free_slab(struct kmem_cache *s, struct page *page)
{
if (unlikely(s->flags & SLAB_TYPESAFE_BY_RCU)) {
- struct rcu_head *head;
-
- if (need_reserve_slab_rcu) {
- int order = compound_order(page);
- int offset = (PAGE_SIZE << order) - s->reserved;
-
- VM_BUG_ON(s->reserved != sizeof(*head));
- head = page_address(page) + offset;
- } else {
- head = &page->rcu_head;
- }
-
- call_rcu(head, rcu_free_slab);
+ call_rcu(&page->rcu_head, rcu_free_slab);
} else
__free_slab(s, page);
}
@@ -3578,9 +3558,6 @@ static int kmem_cache_open(struct kmem_cache *s, slab_flags_t flags)
s->random = get_random_long();
#endif
- if (need_reserve_slab_rcu && (s->flags & SLAB_TYPESAFE_BY_RCU))
- s->reserved = sizeof(struct rcu_head);
-
if (!calculate_sizes(s, -1))
goto error;
if (disable_higher_order_debug) {
--
2.17.0
