Function vm_map_entry_link

freebsd/vm/vm_map.c:1417–1473

* vm_map_entry_{un,}link: * * Insert/remove entries from maps. On linking, if new entry clips * existing entry, trim existing entry to avoid overlap, and manage * offsets. On unlinking, merge disappearing entry with neighbor, if * called for, and manage offsets. Callers should not modify fields in * entries already mapped. */

 *	entries already mapped.
 */
static void
vm_map_entry_link(vm_map_t map, vm_map_entry_t entry)
{
	vm_map_entry_t header, llist, rlist, root;
	vm_size_t max_free_left, max_free_right;

	CTR3(KTR_VM,
	    "vm_map_entry_link: map %p, nentries %d, entry %p", map,
	    map->nentries, entry);
	VM_MAP_ASSERT_LOCKED(map);
	map->nentries++;
	header = &map->header;
	root = vm_map_splay_split(map, entry->start, 0, &llist, &rlist);
	if (root == NULL) {
		/*
		 * The new entry does not overlap any existing entry in the
		 * map, so it becomes the new root of the map tree.
		 */
		max_free_left = vm_map_splay_merge_pred(header, entry, llist);
		max_free_right = vm_map_splay_merge_succ(header, entry, rlist);
	} else if (entry->start == root->start) {
		/*
		 * The new entry is a clone of root, with only the end field
		 * changed.  The root entry will be shrunk to abut the new
		 * entry, and will be the right child of the new root entry in
		 * the modified map.
		 */
		KASSERT(entry->end < root->end,
		    ("%s: clip_start not within entry", __func__));
		vm_map_splay_findprev(root, &llist);
		root->offset += entry->end - root->start;
		root->start = entry->end;
		max_free_left = vm_map_splay_merge_pred(header, entry, llist);
		max_free_right = root->max_free = vm_size_max(
		    vm_map_splay_merge_pred(entry, root, entry),
		    vm_map_splay_merge_right(header, root, rlist));
	} else {
		/*
		 * The new entry is a clone of root, with only the start field
		 * changed.  The root entry will be shrunk to abut the new
		 * entry, and will be the left child of the new root entry in
		 * the modified map.
		 */
		KASSERT(entry->end == root->end,
		    ("%s: clip_start not within entry", __func__));
		vm_map_splay_findnext(root, &rlist);
		entry->offset += entry->start - root->start;
		root->end = entry->start;
		max_free_left = root->max_free = vm_size_max(
		    vm_map_splay_merge_left(header, root, llist),
		    vm_map_splay_merge_succ(entry, root, entry));
		max_free_right = vm_map_splay_merge_succ(header, entry, rlist);
	}
	entry->max_free = vm_size_max(max_free_left, max_free_right);
	map->root = entry;
	VM_MAP_ASSERT_CONSISTENT(map);
}