Function vm_fault_copy_entry

freebsd/vm/vm_fault.c:1884–2080

* Routine: * vm_fault_copy_entry * Function: * Create new shadow object backing dst_entry with private copy of * all underlying pages. When src_entry is equal to dst_entry, * function implements COW for wired-down map entry. Otherwise, * it forks wired entry into dst_map. * * In/out conditions: * The source and destination maps must be locked for write. * The source map entry must

 *		entry corresponding to a main map entry that is wired down).
 */
void
vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
    vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
    vm_ooffset_t *fork_charge)
{
	vm_object_t backing_object, dst_object, object, src_object;
	vm_pindex_t dst_pindex, pindex, src_pindex;
	vm_prot_t access, prot;
	vm_offset_t vaddr;
	vm_page_t dst_m;
	vm_page_t src_m;
	boolean_t upgrade;

#ifdef	lint
	src_map++;
#endif	/* lint */

	upgrade = src_entry == dst_entry;
	access = prot = dst_entry->protection;

	src_object = src_entry->object.vm_object;
	src_pindex = OFF_TO_IDX(src_entry->offset);

	if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
		dst_object = src_object;
		vm_object_reference(dst_object);
	} else {
		/*
		 * Create the top-level object for the destination entry.
		 * Doesn't actually shadow anything - we copy the pages
		 * directly.
		 */
		dst_object = vm_object_allocate_anon(atop(dst_entry->end -
		    dst_entry->start), NULL, NULL, 0);
#if VM_NRESERVLEVEL > 0
		dst_object->flags |= OBJ_COLORED;
		dst_object->pg_color = atop(dst_entry->start);
#endif
		dst_object->domain = src_object->domain;
		dst_object->charge = dst_entry->end - dst_entry->start;
	}

	VM_OBJECT_WLOCK(dst_object);
	KASSERT(upgrade || dst_entry->object.vm_object == NULL,
	    ("vm_fault_copy_entry: vm_object not NULL"));
	if (src_object != dst_object) {
		dst_entry->object.vm_object = dst_object;
		dst_entry->offset = 0;
		dst_entry->eflags &= ~MAP_ENTRY_VN_EXEC;
	}
	if (fork_charge != NULL) {
		KASSERT(dst_entry->cred == NULL,
		    ("vm_fault_copy_entry: leaked swp charge"));
		dst_object->cred = curthread->td_ucred;
		crhold(dst_object->cred);
		*fork_charge += dst_object->charge;
	} else if ((dst_object->type == OBJT_DEFAULT ||
	    dst_object->type == OBJT_SWAP) &&