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slub,rcu: don't assume the size of struct rcu_head

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The size of struct rcu_head may be changed. When it becomes larger,
it will pollute the page array.

We reserve some some bytes for struct rcu_head when a slab
is allocated in this situation.

Changed from V1:
	use VM_BUG_ON instead BUG_ON

Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
This commit is contained in:
Lai Jiangshan
2011-03-10 15:22:00 +08:00
committed by Pekka Enberg
parent ab9a0f196f
commit da9a638c6f
1 changed files with 25 additions and 5 deletions
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30
mm/slub.c
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@@ -1254,21 +1254,38 @@ static void __free_slab(struct kmem_cache *s, struct page *page)
__free_pages(page, order); __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) static void rcu_free_slab(struct rcu_head *h)
{ {
struct page *page; struct page *page;
page = container_of((struct list_head *)h, struct page, lru); if (need_reserve_slab_rcu)
page = virt_to_head_page(h);
else
page = container_of((struct list_head *)h, struct page, lru);
__free_slab(page->slab, page); __free_slab(page->slab, page);
} }
static void free_slab(struct kmem_cache *s, struct page *page) static void free_slab(struct kmem_cache *s, struct page *page)
{ {
if (unlikely(s->flags & SLAB_DESTROY_BY_RCU)) { if (unlikely(s->flags & SLAB_DESTROY_BY_RCU)) {
/* struct rcu_head *head;
* RCU free overloads the RCU head over the LRU
*/ if (need_reserve_slab_rcu) {
struct rcu_head *head = (void *)&page->lru; 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 {
/*
* RCU free overloads the RCU head over the LRU
*/
head = (void *)&page->lru;
}
call_rcu(head, rcu_free_slab); call_rcu(head, rcu_free_slab);
} else } else
@@ -2356,6 +2373,9 @@ static int kmem_cache_open(struct kmem_cache *s,
s->flags = kmem_cache_flags(size, flags, name, ctor); s->flags = kmem_cache_flags(size, flags, name, ctor);
s->reserved = 0; s->reserved = 0;
if (need_reserve_slab_rcu && (s->flags & SLAB_DESTROY_BY_RCU))
s->reserved = sizeof(struct rcu_head);
if (!calculate_sizes(s, -1)) if (!calculate_sizes(s, -1))
goto error; goto error;
if (disable_higher_order_debug) { if (disable_higher_order_debug) {