md: improve partition detection in md array

md currently uses ->media_changed to make sure rescan_partitions
is call on md array after they are assembled.

However that doesn't happen until the array is opened, which is later
than some people would like.

So use blkdev_ioctl to do the rescan immediately that the
array has been assembled.

This means we can remove all the ->change infrastructure as it was only used
to trigger a partition rescan.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 65814b0..2901d0c 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -3104,6 +3104,7 @@
 	struct gendisk *disk;
 	struct mdk_personality *pers;
 	char b[BDEVNAME_SIZE];
+	struct block_device *bdev;
 
 	if (list_empty(&mddev->disks))
 		/* cannot run an array with no devices.. */
@@ -3331,7 +3332,13 @@
 	md_wakeup_thread(mddev->thread);
 	md_wakeup_thread(mddev->sync_thread); /* possibly kick off a reshape */
 
-	mddev->changed = 1;
+	bdev = bdget_disk(mddev->gendisk, 0);
+	if (bdev) {
+		bd_set_size(bdev, mddev->array_size << 1);
+		blkdev_ioctl(bdev->bd_inode, NULL, BLKRRPART, 0);
+		bdput(bdev);
+	}
+
 	md_new_event(mddev);
 	kobject_uevent(&mddev->gendisk->kobj, KOBJ_CHANGE);
 	return 0;
@@ -3453,7 +3460,6 @@
 			mddev->pers = NULL;
 
 			set_capacity(disk, 0);
-			mddev->changed = 1;
 
 			if (mddev->ro)
 				mddev->ro = 0;
@@ -4593,20 +4599,6 @@
 	return 0;
 }
 
-static int md_media_changed(struct gendisk *disk)
-{
-	mddev_t *mddev = disk->private_data;
-
-	return mddev->changed;
-}
-
-static int md_revalidate(struct gendisk *disk)
-{
-	mddev_t *mddev = disk->private_data;
-
-	mddev->changed = 0;
-	return 0;
-}
 static struct block_device_operations md_fops =
 {
 	.owner		= THIS_MODULE,
@@ -4614,8 +4606,6 @@
 	.release	= md_release,
 	.ioctl		= md_ioctl,
 	.getgeo		= md_getgeo,
-	.media_changed	= md_media_changed,
-	.revalidate_disk= md_revalidate,
 };
 
 static int md_thread(void * arg)