scsi: rescan VPD attributes

The VPD page information might change, so we need to be able to update
it. This patch implements a VPD page rescan whenever the 'rescan' sysfs
attribute is triggered.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Shane Seymour <shane.seymour@hpe.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index d07fb65..b1bf42b 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -782,7 +782,7 @@
 	int vpd_len = SCSI_VPD_PG_LEN;
 	int pg80_supported = 0;
 	int pg83_supported = 0;
-	unsigned char *vpd_buf;
+	unsigned char __rcu *vpd_buf, *orig_vpd_buf = NULL;
 
 	if (sdev->skip_vpd_pages)
 		return;
@@ -828,8 +828,16 @@
 			kfree(vpd_buf);
 			goto retry_pg80;
 		}
+		mutex_lock(&sdev->inquiry_mutex);
+		orig_vpd_buf = sdev->vpd_pg80;
 		sdev->vpd_pg80_len = result;
-		sdev->vpd_pg80 = vpd_buf;
+		rcu_assign_pointer(sdev->vpd_pg80, vpd_buf);
+		mutex_unlock(&sdev->inquiry_mutex);
+		synchronize_rcu();
+		if (orig_vpd_buf) {
+			kfree(orig_vpd_buf);
+			orig_vpd_buf = NULL;
+		}
 		vpd_len = SCSI_VPD_PG_LEN;
 	}
 
@@ -849,8 +857,14 @@
 			kfree(vpd_buf);
 			goto retry_pg83;
 		}
+		mutex_lock(&sdev->inquiry_mutex);
+		orig_vpd_buf = sdev->vpd_pg83;
 		sdev->vpd_pg83_len = result;
-		sdev->vpd_pg83 = vpd_buf;
+		rcu_assign_pointer(sdev->vpd_pg83, vpd_buf);
+		mutex_unlock(&sdev->inquiry_mutex);
+		synchronize_rcu();
+		if (orig_vpd_buf)
+			kfree(orig_vpd_buf);
 	}
 }