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Subject[PATCH -mm 4/6] slqb: record slab's start address in slqb_page

slqb's slab is coloring, it's will be useful that record the
color value or start address in struct slqb_page.

This fix adds a field in struct slqb_page to record slab's
start address, It will be used by kfree_rcu().


struct slqb_page has a field:
struct kmem_cache_list *list;

the corresponding field in struct page is:

union {
struct {
unsigned long private;
struct address_space *mapping;
};
struct kmem_cache *slab;
struct page *first_page;
};

It's large than 'struct kmem_cache_list *list;'
*So we are safe to add a field in struct page.*


(This field will not become a burden in future:)
struct page is very small, this fix uses the last room of
struct page. But if we have to add a more important
field in struct slqb_page in future, We can record slab's
color value in slqb_page instead of start address.
like this:
struct {
unsigned long flags;
atomic_t _count;
u16 inuse; /* use u16 instead */
u16 color; /* of unsigned int */
void *a_more_important_field;
struct kmem_cache_list *list;
void **freelist;
union {
struct list_head lru;
struct rcu_head rcu_head;
};
};

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
diff --git a/mm/slqb.c b/mm/slqb.c
index 48bdf3b..c258ddc 100644
--- a/mm/slqb.c
+++ b/mm/slqb.c
@@ -41,6 +41,7 @@ struct slqb_page {
unsigned long flags; /* mandatory */
atomic_t _count; /* mandatory */
unsigned int inuse; /* Nr of objects */
+ void *s_mem; /* start address */
struct kmem_cache_list *list; /* Pointer to list */
void **freelist; /* LIFO freelist */
union {
@@ -1010,6 +1011,7 @@ static struct slqb_page *new_slab_page(struct kmem_cache *s,
}
set_freepointer(s, last, NULL);

+ page->s_mem = start;
page->freelist = start;
page->inuse = 0;
out:









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