Update the MOS directory on spa_upgrade_errlog()

spa_upgrade_errlog() does not update the MOS directory when the
head_errlog feature is enabled. In this case if spa_errlog_sync() is not
called, the MOS dir references the old errlog_last and errlog_sync
objects. Thus when doing a scrub a panic will occur:

Call Trace:
 dump_stack+0x6d/0x8b
 panic+0x101/0x2e3
 spl_panic+0xcf/0x102 [spl]
 delete_errlog+0x124/0x130 [zfs]
 spa_errlog_sync+0x256/0x260 [zfs]
 spa_sync_iterate_to_convergence+0xe5/0x250 [zfs]
 spa_sync+0x2f7/0x670 [zfs]
 txg_sync_thread+0x22d/0x2d0 [zfs]
 thread_generic_wrapper+0x83/0xa0 [spl]
 kthread+0x104/0x140
 ret_from_fork+0x1f/0x40

Fix this by updating the related MOS directory objects in
spa_upgrade_errlog().

Reviewed-by: Mark Maybee <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: George Amanakis <[email protected]>
Closes openzfs#15279
Closes openzfs#15277
(cherry picked from commit e923bcd)

Author: gamanakis

module/zfs/spa_errlog.c

@@ -727,12 +727,21 @@ spa_upgrade_errlog(spa_t *spa, dmu_tx_t *tx)
 	if (spa->spa_errlog_last != 0) {
 		sync_upgrade_errlog(spa, spa->spa_errlog_last, &newobj, tx);
 		spa->spa_errlog_last = newobj;
+
+		(void) zap_update(spa->spa_meta_objset,
+		    DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_ERRLOG_LAST,
+		    sizeof (uint64_t), 1, &spa->spa_errlog_last, tx);
 	}
 
 	if (spa->spa_errlog_scrub != 0) {
 		sync_upgrade_errlog(spa, spa->spa_errlog_scrub, &newobj, tx);
 		spa->spa_errlog_scrub = newobj;
+
+		(void) zap_update(spa->spa_meta_objset,
+		    DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_ERRLOG_SCRUB,
+		    sizeof (uint64_t), 1, &spa->spa_errlog_scrub, tx);
 	}
+
 	mutex_exit(&spa->spa_errlog_lock);
 }