+/*
+ * Completion of a iclog IO does not imply that a transaction has completed, as
+ * transactions can be large enough to span many iclogs. We cannot change the
+ * tail of the log half way through a transaction as this may be the only
+ * transaction in the log and moving the tail to point to the middle of it
+ * will prevent recovery from finding the start of the transaction. Hence we
+ * should only update the last_sync_lsn if this iclog contains transaction
+ * completion callbacks on it.
+ *
+ * We have to do this before we drop the icloglock to ensure we are the only one
+ * that can update it.
+ *
+ * If we are moving the last_sync_lsn forwards, we also need to ensure we kick
+ * the reservation grant head pushing. This is due to the fact that the push
+ * target is bound by the current last_sync_lsn value. Hence if we have a large
+ * amount of log space bound up in this committing transaction then the
+ * last_sync_lsn value may be the limiting factor preventing tail pushing from
+ * freeing space in the log. Hence once we've updated the last_sync_lsn we
+ * should push the AIL to ensure the push target (and hence the grant head) is
+ * no longer bound by the old log head location and can move forwards and make
+ * progress again.
+ */
+static void
+xlog_state_set_callback(
+ struct xlog *log,
+ struct xlog_in_core *iclog,
+ xfs_lsn_t header_lsn)
+{
+ iclog->ic_state = XLOG_STATE_CALLBACK;
+
+ ASSERT(XFS_LSN_CMP(atomic64_read(&log->l_last_sync_lsn),
+ header_lsn) <= 0);
+
+ if (list_empty_careful(&iclog->ic_callbacks))
+ return;
+
+ atomic64_set(&log->l_last_sync_lsn, header_lsn);
+ xlog_grant_push_ail(log, 0);
+}
+