[PATCH 2/3 V2] slub,rcu: don't assume the size of struct rcu_head
From: Lai Jiangshan <hidden>
Date: 2011-03-10 07:20:30
Also in:
linux-mm, lkml
Subsystem:
memory management, slab allocator, the rest · Maintainers:
Andrew Morton, Vlastimil Babka, Harry Yoo, Linus Torvalds
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 Signed-off-by: Lai Jiangshan <redacted> Acked-by: Christoph Lameter <redacted> --- mm/slub.c | 30 +++++++++++++++++++++++++----- 1 files changed, 25 insertions(+), 5 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index d3d1767..ebba3eb 100644
--- a/mm/slub.c
+++ b/mm/slub.c@@ -1254,21 +1254,38 @@ 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; - 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); } static void free_slab(struct kmem_cache *s, struct page *page) { if (unlikely(s->flags & SLAB_DESTROY_BY_RCU)) { - /* - * RCU free overloads the RCU head over the LRU - */ - struct rcu_head *head = (void *)&page->lru; + 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 { + /* + * RCU free overloads the RCU head over the LRU + */ + head = (void *)&page->lru; + } call_rcu(head, rcu_free_slab); } else
@@ -2356,6 +2373,9 @@ static int kmem_cache_open(struct kmem_cache *s, s->flags = kmem_cache_flags(size, flags, name, ctor); 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)) goto error; if (disable_higher_order_debug) { --
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