ocfs2: Only bug out in direct io write for reflinked extent.

In ocfs2_direct_IO_get_blocks, we only need to bug out
in case of we are going to write a recounted extent rec.

What a silly bug introduced by me!
Signed-off-by: NTao Ma <tao.ma@oracle.com>
Signed-off-by: NJoel Becker <joel.becker@oracle.com>
Cc: stable@kernel.org

fs/ocfs2/aops.c

@@ -577,8 +577,9 @@ static int ocfs2_direct_IO_get_blocks(struct inode *inode, sector_t iblock,
 		goto bail;
 	}
 
-	/* We should already CoW the refcounted extent. */
-	BUG_ON(ext_flags & OCFS2_EXT_REFCOUNTED);
+	/* We should already CoW the refcounted extent in case of create. */
+	BUG_ON(create && (ext_flags & OCFS2_EXT_REFCOUNTED));
+
 	/*
 	 * get_more_blocks() expects us to describe a hole by clearing
 	 * the mapped bit on bh_result().