scsi: core: Don't wait for quiesce in scsi_device_block()

scsi_device_block() is only called from scsi_target_block(), which calls it
repeatedly for every child device. For targets with many devices, waiting
for every queue to quiesce may cause a substantial delay (we measured more
than 100s delay for blocking a FC rport with 2048 LUNs).

Just call blk_mq_wait_quiesce_done() once from scsi_target_block() after
stopping all queues.

Signed-off-by: Martin Wilck <mwilck@suse.com>
Link: https://lore.kernel.org/r/20230614103616.31857-6-mwilck@suse.com
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 4b46dcba764932ee4b3ae82b918dc70671f1ef0b..b98750028044c8359495cce332402abd834bcb19 100644 (file)
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2771,8 +2771,9 @@ EXPORT_SYMBOL_GPL(scsi_internal_device_block_nowait);
  * @sdev: device to block
  * @data: dummy argument, ignored
  *
- * Pause SCSI command processing on the specified device and wait until all
- * ongoing scsi_queue_rq() calls have finished. May sleep.
+ * Pause SCSI command processing on the specified device. Callers must wait
+ * until all ongoing scsi_queue_rq() calls have finished after this function
+ * returns.
  *
  * Note:
  * This routine transitions the device to the SDEV_BLOCK state (which must be
@@ -2786,17 +2787,15 @@ static void scsi_device_block(struct scsi_device *sdev, void *data)
 
        mutex_lock(&sdev->state_mutex);
        err = __scsi_internal_device_block_nowait(sdev);
-       if (err == 0) {
+       if (err == 0)
                /*
                 * scsi_stop_queue() must be called with the state_mutex
                 * held. Otherwise a simultaneous scsi_start_queue() call
                 * might unquiesce the queue before we quiesce it.
                 */
                scsi_stop_queue(sdev);
-               mutex_unlock(&sdev->state_mutex);
-               blk_mq_wait_quiesce_done(sdev->request_queue->tag_set);
-       } else
-               mutex_unlock(&sdev->state_mutex);
+
+       mutex_unlock(&sdev->state_mutex);
 
        WARN_ONCE(err, "__scsi_internal_device_block_nowait(%s) failed: err = %d\n",
                  dev_name(&sdev->sdev_gendev), err);
@@ -2894,11 +2893,15 @@ target_block(struct device *dev, void *data)
 void
 scsi_target_block(struct device *dev)
 {
+       struct Scsi_Host *shost = dev_to_shost(dev);
+
        if (scsi_is_target_device(dev))
                starget_for_each_device(to_scsi_target(dev), NULL,
                                        scsi_device_block);
        else
                device_for_each_child(dev, NULL, target_block);
+
+       blk_mq_wait_quiesce_done(&shost->tag_set);
 }
 EXPORT_SYMBOL_GPL(scsi_target_block);