Btrfs: Remove the invalid shrink size check up from btrfs_shrink_dev()

Remove an invalid size check up from btrfs_shrink_dev().

The new size should not larger than the device->total_bytes as it was
already verified before coming to here(i.e. new_size < old_size).

Remove invalid check up for btrfs_shrink_dev().
Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

fs/btrfs/ioctl.c

@@ -1409,7 +1409,7 @@ static noinline int btrfs_ioctl_resize(struct btrfs_root *root,
 		btrfs_commit_transaction(trans, root);
 	} else if (new_size < old_size) {
 		ret = btrfs_shrink_device(device, new_size);
-	}
+	} /* equal, nothing need to do */
 
 out_free:
 	kfree(vol_args);

fs/btrfs/volumes.c

@@ -3059,9 +3059,6 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size)
 	u64 old_size = device->total_bytes;
 	u64 diff = device->total_bytes - new_size;
 
-	if (new_size >= device->total_bytes)
-		return -EINVAL;
-
 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;