md: destroy partitions and notify udev when md array is stopped.

md arrays are not currently destroyed when they are stopped - they
remain in /sys/block.  Last time I tried this I tripped over locking
too much.

A consequence of this is that udev doesn't remove anything from /dev.
This is rather ugly.

As an interim measure until proper device removal can be achieved,
make sure all partitions are removed using the BLKRRPART ioctl, and
send a KOBJ_CHANGE when an md array is stopped.

Signed-off-by: NeilBrown <neilb@suse.de>

drivers/md/md.c

@@ -3884,6 +3884,7 @@ static int do_md_stop(mddev_t * mddev, int mode, int is_open)
 	if (mode == 0) {
 		mdk_rdev_t *rdev;
 		struct list_head *tmp;
+		struct block_device *bdev;
 
 		printk(KERN_INFO "md: %s stopped.\n", mdname(mddev));
 
@@ -3940,6 +3941,12 @@ static int do_md_stop(mddev_t * mddev, int mode, int is_open)
 		mddev->degraded = 0;
 		mddev->barriers_work = 0;
 		mddev->safemode = 0;
+		bdev = bdget_disk(mddev->gendisk, 0);
+		if (bdev) {
+			blkdev_ioctl(bdev, 0, BLKRRPART, 0);
+			bdput(bdev);
+		}
+		kobject_uevent(&disk_to_dev(mddev->gendisk)->kobj, KOBJ_CHANGE);
 
 	} else if (mddev->pers)
 		printk(KERN_INFO "md: %s switched to read-only mode.\n",