struct vm_struct {
struct vm_struct *next;
void *addr;
unsigned long size;
unsigned long flags;
struct page **pages;
#ifdef CONFIG_HAVE_ARCH_HUGE_VMALLOC
unsigned int page_order;
#endif
unsigned int nr_pages;
phys_addr_t phys_addr;
const void *caller;
};
struct vmap_area {
unsigned long va_start;
unsigned long va_end;
struct rb_node rb_node; /* address sorted rbtree */
struct list_head list; /* address sorted list */
/*
* The following two variables can be packed, because
* a vmap_area object can be either:
* 1) in "free" tree (root is vmap_area_root)
* 2) or "busy" tree (root is free_vmap_area_root)
*/
union {
unsigned long subtree_max_size; /* in "free" tree */
struct vm_struct *vm; /* in "busy" tree */
};
};
I have a confusion about this part of the kernel code.
Why do kernel developers use two structures for management?
Why didn't they merge the two structures into one?