ZIL: Tune some assertions.

In zil_free_lwb() we should first assert lwb_state or the rest of
assertions can be misleading if it is false.

Add lwb_state assertions in zil_lwb_add_block() to make sure we are
not trying to add elements to lwb_vdev_tree after it was processed.

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by:	Alexander Motin <[email protected]>
Sponsored by:	iXsystems, Inc.
Closes openzfs#15227

module/zfs/zil.c

@@ -814,17 +814,17 @@ static void
 zil_free_lwb(zilog_t *zilog, lwb_t *lwb)
 {
 	ASSERT(MUTEX_HELD(&zilog->zl_lock));
-	ASSERT(!MUTEX_HELD(&lwb->lwb_vdev_lock));
-	VERIFY(list_is_empty(&lwb->lwb_waiters));
-	VERIFY(list_is_empty(&lwb->lwb_itxs));
-	ASSERT(avl_is_empty(&lwb->lwb_vdev_tree));
+	ASSERT(lwb->lwb_state == LWB_STATE_NEW ||
+	    lwb->lwb_state == LWB_STATE_FLUSH_DONE);
 	ASSERT3P(lwb->lwb_child_zio, ==, NULL);
 	ASSERT3P(lwb->lwb_write_zio, ==, NULL);
 	ASSERT3P(lwb->lwb_root_zio, ==, NULL);
 	ASSERT3U(lwb->lwb_alloc_txg, <=, spa_syncing_txg(zilog->zl_spa));
 	ASSERT3U(lwb->lwb_max_txg, <=, spa_syncing_txg(zilog->zl_spa));
-	ASSERT(lwb->lwb_state == LWB_STATE_NEW ||
-	    lwb->lwb_state == LWB_STATE_FLUSH_DONE);
+	VERIFY(list_is_empty(&lwb->lwb_itxs));
+	VERIFY(list_is_empty(&lwb->lwb_waiters));
+	ASSERT(avl_is_empty(&lwb->lwb_vdev_tree));
+	ASSERT(!MUTEX_HELD(&lwb->lwb_vdev_lock));
 
 	/*
 	 * Clear the zilog's field to indicate this lwb is no longer
@@ -1329,6 +1329,9 @@ zil_lwb_add_block(lwb_t *lwb, const blkptr_t *bp)
 	int ndvas = BP_GET_NDVAS(bp);
 	int i;
 
+	ASSERT3S(lwb->lwb_state, !=, LWB_STATE_WRITE_DONE);
+	ASSERT3S(lwb->lwb_state, !=, LWB_STATE_FLUSH_DONE);
+
 	if (zil_nocacheflush)
 		return;