When invoking a scan via the sysfs 'scan' attribute the process
will be blocked until the scan is completed, which can take a
very long time on large installations.
Enabling the 'async_user_scan' parameter moves the actual
LUN scanning to a workqueue, thereby unblocking the process.
Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
---
drivers/scsi/scsi_transport_fc.c | 29 +++++++++++++++++++++++++++--
1 file changed, 27 insertions(+), 2 deletions(-)
diff --git a/drivers/scsi/scsi_transport_fc.c b/drivers/scsi/scsi_transport_fc.c
index 72954a8..af1d35b 100644
--- a/drivers/scsi/scsi_transport_fc.c
+++ b/drivers/scsi/scsi_transport_fc.c
@@ -83,6 +83,21 @@ MODULE_PARM_DESC(disable_target_scan,
"Disable target scan on remote ports (default=0)");
/*
+ * async_user_scan: make 'scan' sysfs attribute asynchronous
+ * on larger installations scanning can take a very long time
+ * during which the process invoking the scan will be blocked
+ * on writing to the 'scan' attribute. Enabling this attribute
+ * will move scanning to a work queue, allowing the process
+ * to return immediately.
+ */
+static bool fc_async_user_scan;
+
+module_param_named(async_user_scan, fc_async_user_scan,
+ bool, S_IRUGO|S_IWUSR);
+MODULE_PARM_DESC(async_user_scan,
+ "Allow for asynchronous user LUN scanning (default=0)");
+
+/*
* Redefine so that we can have same named attributes in the
* sdev/starget/host objects.
*/
@@ -2121,8 +2136,18 @@ fc_user_scan_tgt(struct Scsi_Host *shost, uint channel, uint id, uint lun)
if ((channel == rport->channel) &&
(id == rport->scsi_target_id)) {
- spin_unlock_irqrestore(shost->host_lock, flags);
- scsi_scan_target(&rport->dev, channel, id, lun, 1);
+ if (lun == SCAN_WILD_CARD &&
+ fc_async_user_scan) {
+ if (!(rport->flags & FC_RPORT_SCAN_PENDING)) {
+ rport->flags |= FC_RPORT_SCAN_PENDING;
+ scsi_queue_work(shost,
+ &rport->scan_work);
+ }
+ spin_unlock_irqrestore(shost->host_lock, flags);
+ } else {
+ spin_unlock_irqrestore(shost->host_lock, flags);
+ scsi_scan_target(&rport->dev, channel, id, lun, 1);
+ }
return;
}
}
--
1.8.5.6
--
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