[SCSI] sd,sr: add early detection of medium not present

The current scsi_test_unit_ready() is updated to return sense code
information (in struct scsi_sense_hdr).  The sd and sr drivers are
changed to interpret the sense code return asc 0x3a as no media and
adjust the device status accordingly.
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

drivers/scsi/scsi_ioctl.c

@@ -244,7 +244,7 @@ int scsi_ioctl(struct scsi_device *sdev, int cmd, void __user *arg)
 		return scsi_set_medium_removal(sdev, SCSI_REMOVAL_ALLOW);
 	case SCSI_IOCTL_TEST_UNIT_READY:
 		return scsi_test_unit_ready(sdev, IOCTL_NORMAL_TIMEOUT,
-					    NORMAL_RETRIES);
+					    NORMAL_RETRIES, NULL);
 	case SCSI_IOCTL_START_UNIT:
 		scsi_cmd[0] = START_STOP;
 		scsi_cmd[1] = 0;

drivers/scsi/scsi_lib.c

@@ -1973,27 +1973,57 @@ scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
 }
 EXPORT_SYMBOL(scsi_mode_sense);
 
+/**
+ *	scsi_test_unit_ready - test if unit is ready
+ *	@sdev:	scsi device to change the state of.
+ *	@timeout: command timeout
+ *	@retries: number of retries before failing
+ *	@sshdr_external: Optional pointer to struct scsi_sense_hdr for
+ *		returning sense. Make sure that this is cleared before passing
+ *		in.
+ *
+ *	Returns zero if unsuccessful or an error if TUR failed.  For
+ *	removable media, a return of NOT_READY or UNIT_ATTENTION is
+ *	translated to success, with the ->changed flag updated.
+ **/
 int
-scsi_test_unit_ready(struct scsi_device *sdev, int timeout, int retries)
+scsi_test_unit_ready(struct scsi_device *sdev, int timeout, int retries,
+		     struct scsi_sense_hdr *sshdr_external)
 {
 	char cmd[] = {
 		TEST_UNIT_READY, 0, 0, 0, 0, 0,
 	};
-	struct scsi_sense_hdr sshdr;
+	struct scsi_sense_hdr *sshdr;
 	int result;
 
-	result = scsi_execute_req(sdev, cmd, DMA_NONE, NULL, 0, &sshdr,
+	if (!sshdr_external)
+		sshdr = kzalloc(sizeof(*sshdr), GFP_KERNEL);
+	else
+		sshdr = sshdr_external;
+
+	/* try to eat the UNIT_ATTENTION if there are enough retries */
+	do {
+		result = scsi_execute_req(sdev, cmd, DMA_NONE, NULL, 0, sshdr,
 					  timeout, retries);
+	} while ((driver_byte(result) & DRIVER_SENSE) &&
+		 sshdr && sshdr->sense_key == UNIT_ATTENTION &&
+		 --retries);
+
+	if (!sshdr)
+		/* could not allocate sense buffer, so can't process it */
+		return result;
 
 	if ((driver_byte(result) & DRIVER_SENSE) && sdev->removable) {
 
-		if ((scsi_sense_valid(&sshdr)) &&
-		    ((sshdr.sense_key == UNIT_ATTENTION) ||
-		     (sshdr.sense_key == NOT_READY))) {
+		if ((scsi_sense_valid(sshdr)) &&
+		    ((sshdr->sense_key == UNIT_ATTENTION) ||
+		     (sshdr->sense_key == NOT_READY))) {
 			sdev->changed = 1;
 			result = 0;
 		}
 	}
+	if (!sshdr_external)
+		kfree(sshdr);
 	return result;
 }
 EXPORT_SYMBOL(scsi_test_unit_ready);

drivers/scsi/sd.c

@@ -736,6 +736,7 @@ static int sd_media_changed(struct gendisk *disk)
 {
 	struct scsi_disk *sdkp = scsi_disk(disk);
 	struct scsi_device *sdp = sdkp->device;
+	struct scsi_sense_hdr *sshdr = NULL;
 	int retval;
 
 	SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp, "sd_media_changed\n"));
@@ -766,8 +767,11 @@ static int sd_media_changed(struct gendisk *disk)
 	 */
 	retval = -ENODEV;
 
-	if (scsi_block_when_processing_errors(sdp))
-		retval = scsi_test_unit_ready(sdp, SD_TIMEOUT, SD_MAX_RETRIES);
+	if (scsi_block_when_processing_errors(sdp)) {
+		sshdr  = kzalloc(sizeof(*sshdr), GFP_KERNEL);
+		retval = scsi_test_unit_ready(sdp, SD_TIMEOUT, SD_MAX_RETRIES,
+					      sshdr);
+	}
 
 	/*
 	 * Unable to test, unit probably not ready.   This usually
@@ -775,7 +779,9 @@ static int sd_media_changed(struct gendisk *disk)
 	 * and we will figure it out later once the drive is
 	 * available again.
 	 */
-	if (retval) {
+	if (retval || (scsi_sense_valid(sshdr) &&
+		       /* 0x3a is medium not present */
+		       sshdr->asc == 0x3a)) {
 		set_media_not_present(sdkp);
 		retval = 1;
 		goto out;
@@ -794,6 +800,7 @@ out:
 	if (retval != sdkp->previous_state)
 		sdev_evt_send_simple(sdp, SDEV_EVT_MEDIA_CHANGE, GFP_KERNEL);
 	sdkp->previous_state = retval;
+	kfree(sshdr);
 	return retval;
 }
 

drivers/scsi/sr.c

@@ -179,18 +179,24 @@ static int sr_media_change(struct cdrom_device_info *cdi, int slot)
 {
 	struct scsi_cd *cd = cdi->handle;
 	int retval;
+	struct scsi_sense_hdr *sshdr;
 
 	if (CDSL_CURRENT != slot) {
 		/* no changer support */
 		return -EINVAL;
 	}
 
-	retval = scsi_test_unit_ready(cd->device, SR_TIMEOUT, MAX_RETRIES);
-	if (retval) {
-		/* Unable to test, unit probably not ready.  This usually
-		 * means there is no disc in the drive.  Mark as changed,
-		 * and we will figure it out later once the drive is
-		 * available again.  */
+	sshdr =  kzalloc(sizeof(*sshdr), GFP_KERNEL);
+	retval = scsi_test_unit_ready(cd->device, SR_TIMEOUT, MAX_RETRIES,
+				      sshdr);
+	if (retval || (scsi_sense_valid(sshdr) &&
+		       /* 0x3a is medium not present */
+		       sshdr->asc == 0x3a)) {
+		/* Media not present or unable to test, unit probably not
+		 * ready. This usually means there is no disc in the drive.
+		 * Mark as changed, and we will figure it out later once
+		 * the drive is available again.
+		 */
 		cd->device->changed = 1;
 		/* This will force a flush, if called from check_disk_change */
 		retval = 1;
@@ -213,6 +219,7 @@ out:
 		sdev_evt_send_simple(cd->device, SDEV_EVT_MEDIA_CHANGE,
 				     GFP_KERNEL);
 	cd->previous_state = retval;
+	kfree(sshdr);
 
 	return retval;
 }

include/scsi/scsi_device.h

@@ -295,7 +295,7 @@ extern int scsi_mode_select(struct scsi_device *sdev, int pf, int sp,
 			    struct scsi_mode_data *data,
 			    struct scsi_sense_hdr *);
 extern int scsi_test_unit_ready(struct scsi_device *sdev, int timeout,
-				int retries);
+				int retries, struct scsi_sense_hdr *sshdr);
 extern int scsi_device_set_state(struct scsi_device *sdev,
 				 enum scsi_device_state state);
 extern struct scsi_event *sdev_evt_alloc(enum scsi_device_event evt_type,