Function spa_load_impl

freebsd/contrib/openzfs/module/zfs/spa.c:4634–4885

* Load an existing storage pool, using the config provided. This config * describes which vdevs are part of the pool and is later validated against * partial configs present in each vdev's label and an entire copy of the * config stored in the MOS. */

 * config stored in the MOS.
 */
static int
spa_load_impl(spa_t *spa, spa_import_type_t type, char **ereport)
{
	int error = 0;
	boolean_t missing_feat_write = B_FALSE;
	boolean_t checkpoint_rewind =
	    (spa->spa_import_flags & ZFS_IMPORT_CHECKPOINT);
	boolean_t update_config_cache = B_FALSE;

	ASSERT(MUTEX_HELD(&spa_namespace_lock));
	ASSERT(spa->spa_config_source != SPA_CONFIG_SRC_NONE);

	spa_load_note(spa, "LOADING");

	error = spa_ld_mos_with_trusted_config(spa, type, &update_config_cache);
	if (error != 0)
		return (error);

	/*
	 * If we are rewinding to the checkpoint then we need to repeat
	 * everything we've done so far in this function but this time
	 * selecting the checkpointed uberblock and using that to open
	 * the MOS.
	 */
	if (checkpoint_rewind) {
		/*
		 * If we are rewinding to the checkpoint update config cache
		 * anyway.
		 */
		update_config_cache = B_TRUE;

		/*
		 * Extract the checkpointed uberblock from the current MOS
		 * and use this as the pool's uberblock from now on. If the
		 * pool is imported as writeable we also write the checkpoint
		 * uberblock to the labels, making the rewind permanent.
		 */
		error = spa_ld_checkpoint_rewind(spa);
		if (error != 0)
			return (error);

		/*
		 * Redo the loading process again with the
		 * checkpointed uberblock.
		 */
		spa_ld_prepare_for_reload(spa);
		spa_load_note(spa, "LOADING checkpointed uberblock");
		error = spa_ld_mos_with_trusted_config(spa, type, NULL);
		if (error != 0)
			return (error);
	}

	/*
	 * Retrieve the checkpoint txg if the pool has a checkpoint.
	 */
	error = spa_ld_read_checkpoint_txg(spa);
	if (error != 0)
		return (error);