mm/vmalloc.c: change void* into explict vm_struct*

vmap_area->private is void* but we don't use the field for various purpose
but use only for vm_struct.  So change it to a vm_struct* with naming to
improve for readability and type checking.
Signed-off-by: Minchan Kim <minchan@kernel.org>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/vmalloc.c

@@ -256,7 +256,7 @@ struct vmap_area {
 	struct rb_node rb_node;		/* address sorted rbtree */
 	struct list_head list;		/* address sorted list */
 	struct list_head purge_list;	/* "lazy purge" list */
-	void *private;
+	struct vm_struct *vm;
 	struct rcu_head rcu_head;
 };
 
@@ -1285,7 +1285,7 @@ static void setup_vmalloc_vm(struct vm_struct *vm, struct vmap_area *va,
 	vm->addr = (void *)va->va_start;
 	vm->size = va->va_end - va->va_start;
 	vm->caller = caller;
-	va->private = vm;
+	va->vm = vm;
 	va->flags |= VM_VM_AREA;
 }
 
@@ -1408,7 +1408,7 @@ static struct vm_struct *find_vm_area(const void *addr)
 
 	va = find_vmap_area((unsigned long)addr);
 	if (va && va->flags & VM_VM_AREA)
-		return va->private;
+		return va->vm;
 
 	return NULL;
 }
@@ -1427,7 +1427,7 @@ struct vm_struct *remove_vm_area(const void *addr)
 
 	va = find_vmap_area((unsigned long)addr);
 	if (va && va->flags & VM_VM_AREA) {
-		struct vm_struct *vm = va->private;
+		struct vm_struct *vm = va->vm;
 
 		if (!(vm->flags & VM_UNLIST)) {
 			struct vm_struct *tmp, **p;