Function vmem_try_fetch

freebsd/kern/subr_vmem.c:1037–1076

}

static int
vmem_try_fetch(vmem_t *vm, const vmem_size_t size, vmem_size_t align, int flags)
{
	vmem_size_t avail;

	VMEM_ASSERT_LOCKED(vm);

	/*
	 * XXX it is possible to fail to meet xalloc constraints with the
	 * imported region.  It is up to the user to specify the
	 * import quantum such that it can satisfy any allocation.
	 */
	if (vmem_import(vm, size, align, flags) == 0)
		return (1);

	/*
	 * Try to free some space from the quantum cache or reclaim
	 * functions if available.
	 */
	if (vm->vm_qcache_max != 0 || vm->vm_reclaimfn != NULL) {
		avail = vm->vm_size - vm->vm_inuse;
		bt_save(vm);
		VMEM_UNLOCK(vm);
		if (vm->vm_qcache_max != 0)
			qc_drain(vm);
		if (vm->vm_reclaimfn != NULL)
			vm->vm_reclaimfn(vm, flags);
		VMEM_LOCK(vm);
		bt_restore(vm);
		/* If we were successful retry even NOWAIT. */
		if (vm->vm_size - vm->vm_inuse > avail)
			return (1);
	}
	if ((flags & M_NOWAIT) != 0)
		return (0);
	bt_save(vm);
	VMEM_CONDVAR_WAIT(vm);
	bt_restore(vm);
	return (1);
}

static int
vmem_try_release(vmem_t *vm, struct vmem_btag *bt, const bool remfree)