7743 per-vdev-zaps have no initialize path on upgrade

Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Don Brady <don.brady@intel.com>

When loading a pool that had been created before the existance of
per-vdev zaps, on a system that knows about per-vdev zaps, the
per-vdev zaps will not be allocated and initialized.

This appears to be because the logic that would have done so, in
spa_sync_config_object(), is not reached under normal operation. It is
only reached if spa_config_dirty_list is non-empty.

The fix is to add another `AVZ_ACTION_` enum that will allow this code
to be reached when we detect that we're loading an old pool, even when
there are no dirty configs.

Closes #272

Author: pcd1193182

usr/src/uts/common/fs/zfs/spa.c

@@ -2657,10 +2657,14 @@ spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
 	error = spa_dir_prop(spa, DMU_POOL_VDEV_ZAP_MAP,
 	    &spa->spa_all_vdev_zaps);
 
-	if (error != ENOENT && error != 0) {
+	if (error == ENOENT) {
+		VERIFY(!nvlist_exists(mos_config,
+		    ZPOOL_CONFIG_HAS_PER_VDEV_ZAPS));
+		spa->spa_avz_action = AVZ_ACTION_INITIALIZE;
+		ASSERT0(vdev_count_verify_zaps(spa->spa_root_vdev));
+	} else if (error != 0) {
 		return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
-	} else if (error == 0 && !nvlist_exists(mos_config,
-	    ZPOOL_CONFIG_HAS_PER_VDEV_ZAPS)) {
+	} else if (!nvlist_exists(mos_config, ZPOOL_CONFIG_HAS_PER_VDEV_ZAPS)) {
 		/*
 		 * An older version of ZFS overwrote the sentinel value, so
 		 * we have orphaned per-vdev ZAPs in the MOS. Defer their
@@ -6156,6 +6160,7 @@ spa_sync_config_object(spa_t *spa, dmu_tx_t *tx)
 	spa_config_enter(spa, SCL_STATE, FTAG, RW_READER);
 
 	ASSERT(spa->spa_avz_action == AVZ_ACTION_NONE ||
+	    spa->spa_avz_action == AVZ_ACTION_INITIALIZE ||
 	    spa->spa_all_vdev_zaps != 0);
 
 	if (spa->spa_avz_action == AVZ_ACTION_REBUILD) {

usr/src/uts/common/fs/zfs/sys/spa_impl.h

@@ -119,7 +119,8 @@ typedef struct spa_taskqs {
 typedef enum spa_all_vdev_zap_action {
 	AVZ_ACTION_NONE = 0,
 	AVZ_ACTION_DESTROY,	/* Destroy all per-vdev ZAPs and the AVZ. */
-	AVZ_ACTION_REBUILD	/* Populate the new AVZ, see spa_avz_rebuild */
+	AVZ_ACTION_REBUILD,	/* Populate the new AVZ, see spa_avz_rebuild */
+	AVZ_ACTION_INITIALIZE
 } spa_avz_action_t;
 
 struct spa {