[SCSI] sd: check runtime PM status in sd_shutdown

sd_shutdown is called during reboot/poweroff.
It may fail if parent device, for example, ata port, was runtime suspended.

Fix it by checking runtime PM status of sd.
Exit immediately if sd was runtime suspended already.
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/scsi/sd.c

@@ -50,6 +50,7 @@
 #include <linux/string_helpers.h>
 #include <linux/async.h>
 #include <linux/slab.h>
+#include <linux/pm_runtime.h>
 #include <asm/uaccess.h>
 #include <asm/unaligned.h>
 
@@ -2741,6 +2742,9 @@ static void sd_shutdown(struct device *dev)
 	if (!sdkp)
 		return;         /* this can happen */
 
+	if (pm_runtime_suspended(dev))
+		goto exit;
+
 	if (sdkp->WCE) {
 		sd_printk(KERN_NOTICE, sdkp, "Synchronizing SCSI cache\n");
 		sd_sync_cache(sdkp);
@@ -2751,6 +2755,7 @@ static void sd_shutdown(struct device *dev)
 		sd_start_stop_device(sdkp, 0);
 	}
 
+exit:
 	scsi_disk_put(sdkp);
 }