[SCSI] sd: implement sd_check_events()

Replace sd_media_change() with sd_check_events().

* Move media removed logic into set_media_not_present() and
  media_not_present() and set sdev->changed iff an existing media is
  removed or the device indicates UNIT_ATTENTION.

* Make sd_check_events() sets sdev->changed if previously missing
  media becomes present.

* Event is reported only if sdev->changed is set.

This makes media presence event reported if scsi_disk->media_present
actually changed or the device indicated UNIT_ATTENTION.  For backward
compatibility, SDEV_EVT_MEDIA_CHANGE is generated each time
sd_check_events() detects media change event.

[jejb: fix boot failure]
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

drivers/scsi/sd.c

@@ -990,30 +990,51 @@ out:
 
 static void set_media_not_present(struct scsi_disk *sdkp)
 {
+	if (sdkp->media_present)
+		sdkp->device->changed = 1;
+
+	if (sdkp->device->removable) {
 		sdkp->media_present = 0;
 		sdkp->capacity = 0;
-	sdkp->device->changed = 1;
+	}
+}
+
+static int media_not_present(struct scsi_disk *sdkp,
+			     struct scsi_sense_hdr *sshdr)
+{
+	if (!scsi_sense_valid(sshdr))
+		return 0;
+
+	/* not invoked for commands that could return deferred errors */
+	switch (sshdr->sense_key) {
+	case UNIT_ATTENTION:
+	case NOT_READY:
+		/* medium not present */
+		if (sshdr->asc == 0x3A) {
+			set_media_not_present(sdkp);
+			return 1;
+		}
+	}
+	return 0;
 }
 
 /**
- *	sd_media_changed - check if our medium changed
+ *	sd_check_events - check media events
  *	@disk: kernel device descriptor
+ *	@clearing: disk events currently being cleared
  *
- *	Returns 0 if not applicable or no change; 1 if change
+ *	Returns mask of DISK_EVENT_*.
  *
  *	Note: this function is invoked from the block subsystem.
  **/
-static int sd_media_changed(struct gendisk *disk)
+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_sense_hdr *sshdr = NULL;
 	int retval;
 
-	SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp, "sd_media_changed\n"));
+	SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp, "sd_check_events\n"));
-
-	if (!sdp->removable)
-		return 0;
 
 	/*
 	 * If the device is offline, don't send any commands - just pretend as
@@ -1043,40 +1064,37 @@ static int sd_media_changed(struct gendisk *disk)
 					      sshdr);
 	}
 
-	if (retval) {
+	/* failed to execute TUR, assume media not present */
+	if (host_byte(retval)) {
 		set_media_not_present(sdkp);
 		goto out;
 	}
 
+	if (media_not_present(sdkp, sshdr))
+		goto out;
+
 	/*
 	 * For removable scsi disk we have to recognise the presence
-	 * of a disk in the drive. This is kept in the struct scsi_disk
+	 * of a disk in the drive.
-	 * struct and tested at open !  Daniel Roche (dan@lectra.fr)
 	 */
+	if (!sdkp->media_present)
+		sdp->changed = 1;
 	sdkp->media_present = 1;
-
 out:
 	/*
-	 * Report a media change under the following conditions:
+	 * sdp->changed is set under the following conditions:
 	 *
-	 *	Medium is present now and wasn't present before.
+	 *	Medium present state has changed in either direction.
-	 *	Medium wasn't present before and is present now.
+	 *	Device has indicated UNIT_ATTENTION.
-	 *	Medium was present at all times, but it changed while
-	 *		we weren't looking (sdp->changed is set).
 	 *
-	 * If there was no medium before and there is no medium now then
+	 * Report SDEV_EVT_MEDIA_CHANGE too for backward compatibility.
-	 * don't report a change, even if a medium was inserted and removed
-	 * while we weren't looking.
 	 */
-	retval = (sdkp->media_present != sdkp->previous_state ||
+	if (sdp->changed)
-			(sdkp->media_present && sdp->changed));
-	if (retval)
 		sdev_evt_send_simple(sdp, SDEV_EVT_MEDIA_CHANGE, GFP_KERNEL);
-	sdkp->previous_state = sdkp->media_present;
-
-	/* sdp->changed indicates medium was changed or is not present */
-	sdp->changed = !sdkp->media_present;
 	kfree(sshdr);
+
+	retval = sdp->changed ? DISK_EVENT_MEDIA_CHANGE : 0;
+	sdp->changed = 0;
 	return retval;
 }
 
@@ -1169,7 +1187,7 @@ static const struct block_device_operations sd_fops = {
 #ifdef CONFIG_COMPAT
 	.compat_ioctl		= sd_compat_ioctl,
 #endif
-	.media_changed		= sd_media_changed,
+	.check_events		= sd_check_events,
 	.revalidate_disk	= sd_revalidate_disk,
 	.unlock_native_capacity	= sd_unlock_native_capacity,
 };
@@ -1312,23 +1330,6 @@ static int sd_done(struct scsi_cmnd *SCpnt)
 	return good_bytes;
 }
 
-static int media_not_present(struct scsi_disk *sdkp,
-			     struct scsi_sense_hdr *sshdr)
-{
-
-	if (!scsi_sense_valid(sshdr))
-		return 0;
-	/* not invoked for commands that could return deferred errors */
-	if (sshdr->sense_key != NOT_READY &&
-	    sshdr->sense_key != UNIT_ATTENTION)
-		return 0;
-	if (sshdr->asc != 0x3A) /* medium not present */
-		return 0;
-
-	set_media_not_present(sdkp);
-	return 1;
-}
-
 /*
  * spinup disk - called only in sd_revalidate_disk()
  */
@@ -1503,7 +1504,7 @@ static void read_capacity_error(struct scsi_disk *sdkp, struct scsi_device *sdp,
 	 */
 	if (sdp->removable &&
 	    sense_valid && sshdr->sense_key == NOT_READY)
-		sdp->changed = 1;
+		set_media_not_present(sdkp);
 
 	/*
 	 * We used to set media_present to 0 here to indicate no media
@@ -2389,8 +2390,10 @@ static void sd_probe_async(void *data, async_cookie_t cookie)
 
 	gd->driverfs_dev = &sdp->sdev_gendev;
 	gd->flags = GENHD_FL_EXT_DEVT;
-	if (sdp->removable)
+	if (sdp->removable) {
 		gd->flags |= GENHD_FL_REMOVABLE;
+		gd->events |= DISK_EVENT_MEDIA_CHANGE;
+	}
 
 	add_disk(gd);
 	sd_dif_config_host(sdkp);
@@ -2472,7 +2475,6 @@ static int sd_probe(struct device *dev)
 	sdkp->disk = gd;
 	sdkp->index = index;
 	atomic_set(&sdkp->openers, 0);
-	sdkp->previous_state = 1;
 
 	if (!sdp->request_queue->rq_timeout) {
 		if (sdp->type != TYPE_MOD)

drivers/scsi/sd.h

@@ -55,7 +55,6 @@ struct scsi_disk {
 	u8		media_present;
 	u8		write_prot;
 	u8		protection_type;/* Data Integrity Field */
-	unsigned	previous_state : 1;
 	unsigned	ATO : 1;	/* state of disk ATO bit */
 	unsigned	WCE : 1;	/* state of disk WCE bit */
 	unsigned	RCD : 1;	/* state of disk RCD bit, unused */