ide: unexport DISK_EVENT_MEDIA_CHANGE for ide-gd and ide-cd

check_events() implementations in both ide-gd and ide-cd are
inadequate for in-kernel event polling. Both generate media change
events continuously when certain conditions are met causing infinite
event loop between the driver and userland event handler.

As disk event now supports suppression of unlisted events, simply
de-listing DISK_EVENT_MEDIA_CHANGE from disk->events resolves the
problem. Internal handling around media revalidation will behave the
same while userland will fall back to userland event polling after
detecting the device doesn't support disk events.

Signed-off-by: Tejun Heo <[e-mail]>
Reported-by: Jens Axboe <[e-mail]>
Acked-by: "David S. Miller" <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>

drivers/ide/ide-cd.c

···
 	ide_cd_read_toc(drive, &sense);
 	g->fops = &idecd_ops;
 	g->flags |= GENHD_FL_REMOVABLE;
-	g->events = DISK_EVENT_MEDIA_CHANGE;
 	add_disk(g);
 	return 0;
 

drivers/ide/ide-cd_ioctl.c

···
 	return CDS_DRIVE_NOT_READY;
 }
 
+/*
+ * ide-cd always generates media changed event if media is missing, which
+ * makes it impossible to use for proper event reporting, so disk->events
+ * is cleared to 0 and the following function is used only to trigger
+ * revalidation and never propagated to userland.
+ */
 unsigned int ide_cdrom_check_events_real(struct cdrom_device_info *cdi,
 					 unsigned int clearing, int slot_nr)
 {

drivers/ide/ide-gd.c

···
 		return 0;
 	}
 
+	/*
+	 * The following is used to force revalidation on the first open on
+	 * removeable devices, and never gets reported to userland as
+	 * genhd->events is 0.  This is intended as removeable ide disk
+	 * can't really detect MEDIA_CHANGE events.
+	 */
 	ret = drive->dev_flags & IDE_DFLAG_MEDIA_CHANGED;
 	drive->dev_flags &= ~IDE_DFLAG_MEDIA_CHANGED;
 
···
 	if (drive->dev_flags & IDE_DFLAG_REMOVABLE)
 		g->flags = GENHD_FL_REMOVABLE;
 	g->fops = &ide_gd_ops;
-	g->events = DISK_EVENT_MEDIA_CHANGE;
 	add_disk(g);
 	return 0;