ext4: fix ext4 mismerge back in January

Duplicate caused, AFAICS, by mismerge in
ff9cb1c4eead5e4c292e75cd3170a82d66944101>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org

fs/ext4/ioctl.c

@@ -268,7 +268,6 @@ group_extend_out:
 		err = ext4_move_extents(filp, donor_filp, me.orig_start,
 					me.donor_start, me.len, &me.moved_len);
 		mnt_drop_write_file(filp);
-		mnt_drop_write(filp->f_path.mnt);
 
 		if (copy_to_user((struct move_extent __user *)arg,
 				 &me, sizeof(me)))