[PATCH 3.12 24/60] sd: get disk reference in sd_check_events()

[Jiri Slaby]

From: Hannes Reinecke <hare@xxxxxxx>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit eb72d0bb84eee5d0dc3044fd17b75e7101dabb57 upstream.

sd_check_events() is called asynchronously, and might race
with device removal. So always take a disk reference when
processing the event to avoid the device being removed while
the event is processed.

Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
Reviewed-by: Ewan D. Milne <emilne@xxxxxxxxxx>
Reviewed-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Cc: Jinpu Wang <jinpu.wang@xxxxxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 drivers/scsi/sd.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index f1e3b5398887..bf7ff64ac7eb 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1365,11 +1365,15 @@ static int media_not_present(struct scsi_disk *sdkp,
  **/
 static unsigned int sd_check_events(struct gendisk *disk, unsigned int clearing)
 {
-	struct scsi_disk *sdkp = scsi_disk(disk);
-	struct scsi_device *sdp = sdkp->device;
+	struct scsi_disk *sdkp = scsi_disk_get(disk);
+	struct scsi_device *sdp;
 	struct scsi_sense_hdr *sshdr = NULL;
 	int retval;
 
+	if (!sdkp)
+		return 0;
+
+	sdp = sdkp->device;
 	SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp, "sd_check_events\n"));
 
 	/*
@@ -1426,6 +1430,7 @@ out:
 	kfree(sshdr);
 	retval = sdp->changed ? DISK_EVENT_MEDIA_CHANGE : 0;
 	sdp->changed = 0;
+	scsi_disk_put(sdkp);
 	return retval;
 }
 
-- 
2.12.0