[SCSI] sd: Add runtime pm in the sd_check_events()

The sd_check_event() will be called periodly even when the device is in the
suspended status to check media event. The scsi_test_unit_ready() in the
sd_check_event() will issue scsi cmd request. Issuing scsi request when the
device is in the suspeneded status will cause problem. For example, when a usb
flash disk in the suspended status, scsi_test_unit_ready() issues a scsi
request. The request will be returned as failed because the usb device is not
active. The patch adds scsi_autopm_get_device() and scsi_autopm_put_device()
around scsi_test_unit_ready() in the sd_check_event() to resolve such problem.

Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

drivers/scsi/sd.c

@@ -1212,9 +1212,14 @@ static unsigned int sd_check_events(struct gendisk *disk, unsigned int clearing)
 	retval = -ENODEV;
 
 	if (scsi_block_when_processing_errors(sdp)) {
+		retval = scsi_autopm_get_device(sdp);
+		if (retval)
+			goto out;
+
 		sshdr  = kzalloc(sizeof(*sshdr), GFP_KERNEL);
 		retval = scsi_test_unit_ready(sdp, SD_TIMEOUT, SD_MAX_RETRIES,
 					      sshdr);
+		scsi_autopm_put_device(sdp);
 	}
 
 	/* failed to execute TUR, assume media not present */