Function vm_page_release_toq

freebsd/vm/vm_page.c:4146–4186

* Release a page back to the page queues in preparation for unwiring. */

 * Release a page back to the page queues in preparation for unwiring.
 */
static void
vm_page_release_toq(vm_page_t m, uint8_t nqueue, const bool noreuse)
{
	vm_page_astate_t old, new;
	uint16_t nflag;

	/*
	 * Use a check of the valid bits to determine whether we should
	 * accelerate reclamation of the page.  The object lock might not be
	 * held here, in which case the check is racy.  At worst we will either
	 * accelerate reclamation of a valid page and violate LRU, or
	 * unnecessarily defer reclamation of an invalid page.
	 *
	 * If we were asked to not cache the page, place it near the head of the
	 * inactive queue so that is reclaimed sooner.
	 */
	if (noreuse || m->valid == 0) {
		nqueue = PQ_INACTIVE;
		nflag = PGA_REQUEUE_HEAD;
	} else {
		nflag = PGA_REQUEUE;
	}

	old = vm_page_astate_load(m);
	do {
		new = old;

		/*
		 * If the page is already in the active queue and we are not
		 * trying to accelerate reclamation, simply mark it as
		 * referenced and avoid any queue operations.
		 */
		new.flags &= ~PGA_QUEUE_OP_MASK;
		if (nflag != PGA_REQUEUE_HEAD && old.queue == PQ_ACTIVE)
			new.flags |= PGA_REFERENCED;
		else {
			new.flags |= nflag;
			new.queue = nqueue;
		}
	} while (!vm_page_pqstate_commit(m, &old, new));
}

/*
 * Unwire a page and either attempt to free it or re-add it to the page queues.