Function vm_object_collapse_scan

freebsd/vm/vm_object.c:1763–1891

}

static void
vm_object_collapse_scan(vm_object_t object)
{
	vm_object_t backing_object;
	vm_page_t next, p, pp;
	vm_pindex_t backing_offset_index, new_pindex;

	VM_OBJECT_ASSERT_WLOCKED(object);
	VM_OBJECT_ASSERT_WLOCKED(object->backing_object);

	backing_object = object->backing_object;
	backing_offset_index = OFF_TO_IDX(object->backing_object_offset);

	/*
	 * Our scan
	 */
	for (p = TAILQ_FIRST(&backing_object->memq); p != NULL; p = next) {
		next = TAILQ_NEXT(p, listq);
		new_pindex = p->pindex - backing_offset_index;

		/*
		 * Check for busy page
		 */
		if (vm_page_tryxbusy(p) == 0) {
			next = vm_object_collapse_scan_wait(object, p);
			continue;
		}

		KASSERT(object->backing_object == backing_object,
		    ("vm_object_collapse_scan: backing object mismatch %p != %p",
		    object->backing_object, backing_object));
		KASSERT(p->object == backing_object,
		    ("vm_object_collapse_scan: object mismatch %p != %p",
		    p->object, backing_object));

		if (p->pindex < backing_offset_index ||
		    new_pindex >= object->size) {
			if (backing_object->type == OBJT_SWAP)
				swap_pager_freespace(backing_object, p->pindex,
				    1);

			KASSERT(!pmap_page_is_mapped(p),
			    ("freeing mapped page %p", p));
			if (vm_page_remove(p))
				vm_page_free(p);
			continue;
		}

		if (!vm_page_all_valid(p)) {
			KASSERT(!pmap_page_is_mapped(p),
			    ("freeing mapped page %p", p));
			if (vm_page_remove(p))
				vm_page_free(p);
			continue;
		}

		pp = vm_page_lookup(object, new_pindex);
		if (pp != NULL && vm_page_tryxbusy(pp) == 0) {