Revert "md: improve partition detection in md array"

This reverts commit 5b479c91.

Quoth Neil Brown:

  "It causes an oops when auto-detecting raid arrays, and it doesn't
   seem easy to fix.

   The array may not be 'open' when do_md_run is called, so
   bdev->bd_disk might be NULL, so bd_set_size can oops.

   This whole approach of opening an md device before it has been
   assembled just seems to get more and more painful.  I think I'm going
   to have to come up with something clever to provide both backward
   comparability with usage expectation, and sane integration into the
   rest of the kernel."
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/md/md.c

@@ -3104,7 +3104,6 @@ static int do_md_run(mddev_t * mddev)
 	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.. */
@@ -3332,13 +3331,7 @@ static int do_md_run(mddev_t * mddev)
 	md_wakeup_thread(mddev->thread);
 	md_wakeup_thread(mddev->sync_thread); /* possibly kick off a reshape */
 
-	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);
-	}
-
+	mddev->changed = 1;
 	md_new_event(mddev);
 	kobject_uevent(&mddev->gendisk->kobj, KOBJ_CHANGE);
 	return 0;
@@ -3460,6 +3453,7 @@ static int do_md_stop(mddev_t * mddev, int mode)
 			mddev->pers = NULL;
 
 			set_capacity(disk, 0);
+			mddev->changed = 1;
 
 			if (mddev->ro)
 				mddev->ro = 0;
@@ -4599,6 +4593,20 @@ static int md_release(struct inode *inode, struct file * file)
 	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,
@@ -4606,6 +4614,8 @@ static struct block_device_operations md_fops =
 	.release	= md_release,
 	.ioctl		= md_ioctl,
 	.getgeo		= md_getgeo,
+	.media_changed	= md_media_changed,
+	.revalidate_disk= md_revalidate,
 };
 
 static int md_thread(void * arg)

drivers/md/raid1.c

@@ -2063,6 +2063,7 @@ static int raid1_resize(mddev_t *mddev, sector_t sectors)
 	 */
 	mddev->array_size = sectors>>1;
 	set_capacity(mddev->gendisk, mddev->array_size << 1);
+	mddev->changed = 1;
 	if (mddev->array_size > mddev->size && mddev->recovery_cp == MaxSector) {
 		mddev->recovery_cp = mddev->size << 1;
 		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);

drivers/md/raid5.c

@@ -3864,6 +3864,7 @@ static int raid5_resize(mddev_t *mddev, sector_t sectors)
 	sectors &= ~((sector_t)mddev->chunk_size/512 - 1);
 	mddev->array_size = (sectors * (mddev->raid_disks-conf->max_degraded))>>1;
 	set_capacity(mddev->gendisk, mddev->array_size << 1);
+	mddev->changed = 1;
 	if (sectors/2  > mddev->size && mddev->recovery_cp == MaxSector) {
 		mddev->recovery_cp = mddev->size << 1;
 		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
@@ -3998,6 +3999,7 @@ static void end_reshape(raid5_conf_t *conf)
 		conf->mddev->array_size = conf->mddev->size *
 			(conf->raid_disks - conf->max_degraded);
 		set_capacity(conf->mddev->gendisk, conf->mddev->array_size << 1);
+		conf->mddev->changed = 1;
 
 		bdev = bdget_disk(conf->mddev->gendisk, 0);
 		if (bdev) {

include/linux/raid/md_k.h

@@ -201,6 +201,7 @@ struct mddev_s
 	struct mutex			reconfig_mutex;
 	atomic_t			active;
 
+	int				changed;	/* true if we might need to reread partition info */
 	int				degraded;	/* whether md should consider
 							 * adding a spare
 							 */