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[PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree [message #47902 is a reply to message #47897] Tue, 18 September 2012 14:12 Go to previous messageGo to previous message
Glauber Costa is currently offline  Glauber Costa
Messages: 916
Registered: October 2011
Senior Member
struct page already have this information. If we start chaining
caches, this information will always be more trustworthy than
whatever is passed into the function

A parent pointer is added to the slub structure, so we can make sure
the freeing comes from either the right slab, or from its rightful
parent.

[ v3: added parent testing with VM_BUG_ON ]

Signed-off-by: Glauber Costa <glommer@parallels.com>
CC: Christoph Lameter <cl@linux.com>
CC: Pekka Enberg <penberg@cs.helsinki.fi>
---
mm/slab.c | 5 ++++-
mm/slab.h | 11 +++++++++++
mm/slub.c | 4 +++-
3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index f2d760c..18de3f6 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3938,9 +3938,12 @@ EXPORT_SYMBOL(__kmalloc);
* Free an object which was previously allocated from this
* cache.
*/
-void kmem_cache_free(struct kmem_cache *cachep, void *objp)
+void kmem_cache_free(struct kmem_cache *s, void *objp)
{
unsigned long flags;
+ struct kmem_cache *cachep = virt_to_cache(objp);
+
+ VM_BUG_ON(!slab_equal_or_parent(cachep, s));

local_irq_save(flags);
debug_check_no_locks_freed(objp, cachep->object_size);
diff --git a/mm/slab.h b/mm/slab.h
index 6f2a34d..f2501ab 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -60,11 +60,22 @@ static inline bool cache_match_memcg(struct kmem_cache *cachep,
return cachep->memcg_params.memcg == memcg;
}

+static inline bool slab_equal_or_parent(struct kmem_cache *s,
+ struct kmem_cache *p)
+{
+ return (p == s) || (p == s->memcg_params.parent);
+}
#else
static inline bool cache_match_memcg(struct kmem_cache *cachep,
struct mem_cgroup *memcg)
{
return true;
}
+
+static inline bool slab_equal_or_parent(struct kmem_cache *s,
+ struct kmem_cache *p)
+{
+ return true;
+}
#endif
#endif
diff --git a/mm/slub.c b/mm/slub.c
index 4778548..a045dfc 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2604,7 +2604,9 @@ void kmem_cache_free(struct kmem_cache *s, void *x)

page = virt_to_head_page(x);

- slab_free(s, page, x, _RET_IP_);
+ VM_BUG_ON(!slab_equal_or_parent(page->slab, s));
+
+ slab_free(page->slab, page, x, _RET_IP_);

trace_kmem_cache_free(_RET_IP_, x);
}
--
1.7.11.4

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