内存管理-SLAB(撤销SLAB块slab_destroy())

static void slab_destroy (kmem_cache_t *cachep, struct slab *slabp)
{
/*获得第一个对象的地址*/
void *addr = slabp->s_mem - slabp->colouroff;
#if DEBUG
int i;
for (i = 0; i < cachep->num; i++) {
void *objp = slabp->s_mem + cachep->objsize * i;

if (cachep->flags & SLAB_POISON) {
#ifdef CONFIG_DEBUG_PAGEALLOC
if ((cachep->objsize%PAGE_SIZE)==0 && OFF_SLAB(cachep))
kernel_map_pages(virt_to_page(objp), cachep->objsize/PAGE_SIZE,1);
else
check_poison_obj(cachep, objp);
#else
check_poison_obj(cachep, objp);
#endif
}
if (cachep->flags & SLAB_RED_ZONE) {
if (*dbg_redzone1(cachep, objp) != RED_INACTIVE)
slab_error(cachep, "start of a freed object "
"was overwritten");
if (*dbg_redzone2(cachep, objp) != RED_INACTIVE)
slab_error(cachep, "end of a freed object "
"was overwritten");
}
if (cachep->dtor && !(cachep->flags & SLAB_POISON))
(cachep->dtor)(objp+obj_dbghead(cachep), cachep, 0);
}
#else
/*在撤销slab块的时候调用析构函数，析构每一个对象，在新版本的kernel中，已经没有了析构函数，只有构造函数*/
if (cachep->dtor) {
int i;
for (i = 0; i < cachep->num; i++) {
void* objp = slabp->s_mem+cachep->objsize*i;
(cachep->dtor)(objp, cachep, 0);
}
}
#endif

if (unlikely(cachep->flags & SLAB_DESTROY_BY_RCU)) {
struct slab_rcu *slab_rcu;

slab_rcu = (struct slab_rcu *) slabp;
slab_rcu->cachep = cachep;
slab_rcu->addr = addr;
call_rcu(&slab_rcu->head, kmem_rcu_free);
} else {
/*释放给buddy system*/
kmem_freepages(cachep, addr);
/*如果是外置slab管理对象，则在那个cache中进行销毁*/
if (OFF_SLAB(cachep))
kmem_cache_free(cachep->slabp_cache, slabp);
}
}