Function ztest_freeze

freebsd/contrib/openzfs/cmd/ztest/ztest.c:7052–7140

}

static void
ztest_freeze(void)
{
	ztest_ds_t *zd = &ztest_ds[0];
	spa_t *spa;
	int numloops = 0;

	if (ztest_opts.zo_verbose >= 3)
		(void) printf("testing spa_freeze()...\n");

	kernel_init(SPA_MODE_READ | SPA_MODE_WRITE);
	VERIFY3U(0, ==, spa_open(ztest_opts.zo_pool, &spa, FTAG));
	VERIFY3U(0, ==, ztest_dataset_open(0));
	ztest_spa = spa;

	/*
	 * Force the first log block to be transactionally allocated.
	 * We have to do this before we freeze the pool -- otherwise
	 * the log chain won't be anchored.
	 */
	while (BP_IS_HOLE(&zd->zd_zilog->zl_header->zh_log)) {
		ztest_dmu_object_alloc_free(zd, 0);
		zil_commit(zd->zd_zilog, 0);
	}

	txg_wait_synced(spa_get_dsl(spa), 0);

	/*
	 * Freeze the pool.  This stops spa_sync() from doing anything,
	 * so that the only way to record changes from now on is the ZIL.
	 */
	spa_freeze(spa);

	/*
	 * Because it is hard to predict how much space a write will actually
	 * require beforehand, we leave ourselves some fudge space to write over
	 * capacity.
	 */
	uint64_t capacity = metaslab_class_get_space(spa_normal_class(spa)) / 2;

	/*
	 * Run tests that generate log records but don't alter the pool config
	 * or depend on DSL sync tasks (snapshots, objset create/destroy, etc).
	 * We do a txg_wait_synced() after each iteration to force the txg
	 * to increase well beyond the last synced value in the uberblock.
	 * The ZIL should be OK with that.
	 *
	 * Run a random number of times less than zo_maxloops and ensure we do
	 * not run out of space on the pool.
	 */
	while (ztest_random(10) != 0 &&
	    numloops++ < ztest_opts.zo_maxloops &&
	    metaslab_class_get_alloc(spa_normal_class(spa)) < capacity) {
		ztest_od_t od;
		ztest_od_init(&od, 0, FTAG, 0, DMU_OT_UINT64_OTHER, 0, 0, 0);
		VERIFY0(ztest_object_init(zd, &od, sizeof (od), B_FALSE));
		ztest_io(zd, od.od_object,
		    ztest_random(ZTEST_RANGE_LOCKS) << SPA_MAXBLOCKSHIFT);