- ENTRY;
- if (!it || (it->it_op != IT_GETATTR && it->it_op != IT_LOOKUP)) {
- cfs_mutex_lock(&lck->rpcl_mutex);
- LASSERT(lck->rpcl_it == NULL);
- lck->rpcl_it = it;
- }
+ ENTRY;
+
+ if (it != NULL && (it->it_op == IT_GETATTR || it->it_op == IT_LOOKUP))
+ return;
+
+ /* This would normally block until the existing request finishes.
+ * If fail_loc is set it will block until the regular request is
+ * done, then set rpcl_it to MDC_FAKE_RPCL_IT. Once that is set
+ * it will only be cleared when all fake requests are finished.
+ * Only when all fake requests are finished can normal requests
+ * be sent, to ensure they are recoverable again. */
+ again:
+ cfs_mutex_lock(&lck->rpcl_mutex);
+
+ if (CFS_FAIL_CHECK_QUIET(OBD_FAIL_MDC_RPCS_SEM)) {
+ lck->rpcl_it = MDC_FAKE_RPCL_IT;
+ lck->rpcl_fakes++;
+ cfs_mutex_unlock(&lck->rpcl_mutex);
+ return;
+ }
+
+ /* This will only happen when the CFS_FAIL_CHECK() was
+ * just turned off but there are still requests in progress.
+ * Wait until they finish. It doesn't need to be efficient
+ * in this extremely rare case, just have low overhead in
+ * the common case when it isn't true. */
+ while (unlikely(lck->rpcl_it == MDC_FAKE_RPCL_IT)) {
+ cfs_mutex_unlock(&lck->rpcl_mutex);
+ cfs_schedule_timeout(cfs_time_seconds(1) / 4);
+ goto again;
+ }
+
+ LASSERT(lck->rpcl_it == NULL);
+ lck->rpcl_it = it;