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Subject[PATCH 3/3 V2] slab,rcu: don't assume the size of struct rcu_head
The size of struct rcu_head may be changed. When it becomes larger,
it may pollute the data after struct slab.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
diff --git a/mm/slab.c b/mm/slab.c
index 37961d1..52cf0b4 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -191,22 +191,6 @@ typedef unsigned int kmem_bufctl_t;
#define SLAB_LIMIT (((kmem_bufctl_t)(~0U))-3)

/*
- * struct slab
- *
- * Manages the objs in a slab. Placed either at the beginning of mem allocated
- * for a slab, or allocated from an general cache.
- * Slabs are chained into three list: fully used, partial, fully free slabs.
- */
-struct slab {
- struct list_head list;
- unsigned long colouroff;
- void *s_mem; /* including colour offset */
- unsigned int inuse; /* num of objs active in slab */
- kmem_bufctl_t free;
- unsigned short nodeid;
-};
-
-/*
* struct slab_rcu
*
* slab_destroy on a SLAB_DESTROY_BY_RCU cache uses this structure to
@@ -219,8 +203,6 @@ struct slab {
*
* rcu_read_lock before reading the address, then rcu_read_unlock after
* taking the spinlock within the structure expected at that address.
- *
- * We assume struct slab_rcu can overlay struct slab when destroying.
*/
struct slab_rcu {
struct rcu_head head;
@@ -229,6 +211,27 @@ struct slab_rcu {
};

/*
+ * struct slab
+ *
+ * Manages the objs in a slab. Placed either at the beginning of mem allocated
+ * for a slab, or allocated from an general cache.
+ * Slabs are chained into three list: fully used, partial, fully free slabs.
+ */
+struct slab {
+ union {
+ struct {
+ struct list_head list;
+ unsigned long colouroff;
+ void *s_mem; /* including colour offset */
+ unsigned int inuse; /* num of objs active in slab */
+ kmem_bufctl_t free;
+ unsigned short nodeid;
+ };
+ struct slab_rcu __slab_cover_slab_rcu;
+ };
+};
+
+/*
* struct array_cache
*
* Purpose:
--

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