Revert "loop: cleanup partitions when detaching loop device"

This reverts commit 8761a3dc.

There are situations where the destruction path is called
with the bdev->bd_mutex already held, which then deadlocks in
loop_clr_fd(). The normal partition cleanup does a trylock()
on the mutex, but it'd be nice to have a more bullet proof
method in loop. So punt this more involved fix to the next
merge window, and just back out this buggy fix for now.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/partition-generic.c

@@ -257,7 +257,6 @@ void delete_partition(struct gendisk *disk, int partno)
 
 	hd_struct_put(part);
 }
-EXPORT_SYMBOL(delete_partition);
 
 static ssize_t whole_disk_show(struct device *dev,
 			       struct device_attribute *attr, char *buf)

drivers/block/loop.c

@@ -1044,29 +1044,12 @@ static int loop_clr_fd(struct loop_device *lo)
 	lo->lo_state = Lo_unbound;
 	/* This is safe: open() is still holding a reference. */
 	module_put(THIS_MODULE);
+	if (lo->lo_flags & LO_FLAGS_PARTSCAN && bdev)
+		ioctl_by_bdev(bdev, BLKRRPART, 0);
 	lo->lo_flags = 0;
 	if (!part_shift)
 		lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;
 	mutex_unlock(&lo->lo_ctl_mutex);
-
-	/*
-	 * Remove all partitions, since BLKRRPART won't remove user
-	 * added partitions when max_part=0
-	 */
-	if (bdev) {
-		struct disk_part_iter piter;
-		struct hd_struct *part;
-
-		mutex_lock_nested(&bdev->bd_mutex, 1);
-		invalidate_partition(bdev->bd_disk, 0);
-		disk_part_iter_init(&piter, bdev->bd_disk,
-					DISK_PITER_INCL_EMPTY);
-		while ((part = disk_part_iter_next(&piter)))
-			delete_partition(bdev->bd_disk, part->partno);
-		disk_part_iter_exit(&piter);
-		mutex_unlock(&bdev->bd_mutex);
-	}
-
 	/*
 	 * Need not hold lo_ctl_mutex to fput backing file.
 	 * Calling fput holding lo_ctl_mutex triggers a circular