[PATCH v8 5/5] scsi: core: Handle reprobe for existing devices during SCSI scan

[Brian Bunker <brian@purestorage.com>]

Complement scsi_rescan_device() reprobe by handling the scan path.
When a manual or transport-initiated scan finds a LUN that already has
a fully set up scsi_device, call scsi_rescan_device() for it so that
changes to the standard INQUIRY data are picked up and the device is
reprobed if its peripheral qualifier or device type changed.

The device lock is taken inside scsi_rescan_device() while the host's
scan_mutex is held; that lock order is already used by
scsi_remove_device(). Pseudo devices and devices that are still being
set up by another scan are left alone.

Co-developed-by: Krishna Kant <krishna.kant@purestorage.com>
Signed-off-by: Krishna Kant <krishna.kant@purestorage.com>
Signed-off-by: Brian Bunker <brian@purestorage.com>
---
 drivers/scsi/scsi_scan.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 87fd3ba5c3cc..c6424773c3f1 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -1156,6 +1156,16 @@ static int scsi_probe_and_add_lun(struct Scsi_Host *shost,
 			SCSI_LOG_SCAN_BUS(3, sdev_printk(KERN_INFO, sdev,
 				"scsi scan: device exists on %s\n",
 				dev_name(&sdev->sdev_gendev)));
+			/*
+			 * Rescanning a device that has been fully set up:
+			 * refresh its INQUIRY data so that peripheral
+			 * qualifier or device type changes (e.g. ALUA state
+			 * transitions) are picked up.
+			 */
+			if (rescan != SCSI_SCAN_INITIAL &&
+			    !scsi_device_created(sdev) &&
+			    !scsi_device_is_pseudo_dev(sdev))
+				scsi_rescan_device(sdev);
 			if (sdevp)
 				*sdevp = sdev;
 			else
-- 
2.56.0