zinject: Introduce ready delay fault injection

This adds a pause to the ZIO pipeline in the ready stage for
matching I/O (data, dnode, or raw bookmark).

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Rob Norris <robn@despairlabs.com>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Akash B <akash-b@hpe.com>
Signed-off-by: Robert Evans <evansr@google.com>
Closes #17787

module/zfs/zio.c

@@ -5305,6 +5305,16 @@ zio_ready(zio_t *zio)
 		return (NULL);
 	}
 
+	if (zio_injection_enabled) {
+		hrtime_t target = zio_handle_ready_delay(zio);
+		if (target != 0 && zio->io_target_timestamp == 0) {
+			zio->io_stage >>= 1;
+			zio->io_target_timestamp = target;
+			zio_delay_interrupt(zio);
+			return (NULL);
+		}
+	}
+
 	if (zio->io_ready) {
 		ASSERT(IO_IS_ALLOCATING(zio));
 		ASSERT(BP_GET_BIRTH(bp) == zio->io_txg ||

module/zfs/zio_inject.c

@@ -827,6 +827,44 @@ zio_handle_export_delay(spa_t *spa, hrtime_t elapsed)
 	zio_handle_pool_delay(spa, elapsed, ZINJECT_DELAY_EXPORT);
 }
 
+/*
+ * For testing, inject a delay before ready state.
+ */
+hrtime_t
+zio_handle_ready_delay(zio_t *zio)
+{
+	inject_handler_t *handler;
+	hrtime_t now = gethrtime();
+	hrtime_t target = 0;
+
+	/*
+	 * Ignore I/O not associated with any logical data.
+	 */
+	if (zio->io_logical == NULL)
+		return (0);
+
+	rw_enter(&inject_lock, RW_READER);
+
+	for (handler = list_head(&inject_handlers); handler != NULL;
+	    handler = list_next(&inject_handlers, handler)) {
+		if (zio->io_spa != handler->zi_spa ||
+		    handler->zi_record.zi_cmd != ZINJECT_DELAY_READY)
+			continue;
+
+		/* If this handler matches, inject the delay */
+		if (zio_match_iotype(zio, handler->zi_record.zi_iotype) &&
+		    zio_match_handler(&zio->io_logical->io_bookmark,
+		    zio->io_bp ? BP_GET_TYPE(zio->io_bp) : DMU_OT_NONE,
+		    zio_match_dva(zio), &handler->zi_record, zio->io_error)) {
+			target = now + (hrtime_t)handler->zi_record.zi_timer;
+			break;
+		}
+	}
+
+	rw_exit(&inject_lock);
+	return (target);
+}
+
 static int
 zio_calculate_range(const char *pool, zinject_record_t *record)
 {